1. Introduction
The goal of the CLARIN Federated Content Search (CLARIN-FCS) - Core specification is to introduce an interface specification that decouples the search engine functionality from its exploitation, i.e. user-interfaces, third-party applications, and to allow services to access heterogeneous search engines in a uniform way.
1.1. Terminology
The key words MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD, SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL in this document are to be interpreted as in RFC2119.
1.2. Glossary
- Aggregator
-
A module or service to dispatch queries to repositories and collect results.
- Annotation Layer
-
An annotation layer is the sum of possible annotations for a language resource, such as part of speech or orthographic transcription. Usually it is related to a given annotation task or topic. For the scope of the specification it is used as synonym for annotation tier.
- CLARIN-FCS, FCS
-
CLARIN federated content search, an interface specification to allow searching within resource content of repositories.
- Client
-
A software component, which implements the interface specification to query Endpoints, i.e. an aggregator or a user-interface.
- CQL
-
Contextual Query Language, previously known as Common Query Language, is a domain specific language for representing queries to information retrieval systems such as search engines, bibliographic catalogs and museum collection information.
- Data View
-
A Data View is a mechanism to support different representations of search results, e.g. a "hits with highlights" view, an image or a geolocation.
- Data View Payload, Payload
-
The actual content encoded within a Data View, i.e. a CMDI metadata record or a KML encoded geolocation.
- Endpoint
-
A software component, which implements the CLARIN-FCS interface specification and translates between CLARIN-FCS and a search engine.
- FCS-QL
-
Federated Content Search Query Language is the query language used in the advanced CLARIN-FCS profile. It is derived from Corpus Workbench’s CQP-TUTORIAL.
- Hit
-
A piece of data returned by a Search Engine that matches the search criterion. What is considered a Hit highly depends on Search Engine.
- Interface Specification
-
Common harmonized interface and suite of protocols that repositories need to implement.
- Layer
-
See Annotation Layer.
- PID
-
A Persistent identifier is a long-lasting reference to a digital object.
- Repository
-
A software component at a CLARIN center that stores resources (= data) and information about these resources (= metadata).
- Repository Registry
-
A separate service that allows registering Repositories and their Endpoints and provides information about these to other components, e.g. an Aggregator. The CLARIN Center Registry is an implementation of such a repository registry.
- Resource
-
A searchable and addressable entity at an Endpoint, such as a text corpus or a multi-modal corpus.
- Resource Fragment
-
A smaller unit in a Resource, e.g. a sentence in a text corpus or a time interval in an audio transcription.
- Result Set
-
An (ordered) set of hits that match a search criterion produced by a search engine as the result of processing a query.
- Search Engine
-
A software component within a repository that allows for searching within the repository contents.
- SRU
-
Search and Retrieve via URL is a protocol for Internet search queries. Originally introduced by Library of Congress LOC-SRU12, later standardization process moved to OASIS OASIS-SRU12, OASIS-SRU20.
1.3. Normative References
- RFC2119
-
Key words for use in RFCs to Indicate Requirement Levels, IETF RFC 2119, March 1997, https://www.ietf.org/rfc/rfc2119.html
- XML-Namespaces
-
Namespaces in XML 1.0 (Third Edition), W3C, 8 December 2009, http://www.w3.org/TR/2009/REC-xml-names-20091208/
- OASIS-SRU-Overview
-
searchRetrieve: Part 0. Overview Version 1.0, OASIS, January 2013, http://docs.oasis-open.org/search-ws/searchRetrieve/v1.0/os/part0-overview/searchRetrieve-v1.0-os-part0-overview.doc (HTML), (PDF)
- OASIS-SRU-APD
-
searchRetrieve: Part 1. Abstract Protocol Definition Version 1.0, OASIS, January 2013, http://docs.oasis-open.org/search-ws/searchRetrieve/v1.0/os/part1-apd/searchRetrieve-v1.0-os-part1-apd.doc (HTML), (PDF)
- OASIS-SRU12
-
searchRetrieve: Part 2. SRU searchRetrieve Operation: APD Binding for SRU 1.2 Version 1.0, OASIS, January 2013, http://docs.oasis-open.org/search-ws/searchRetrieve/v1.0/os/part2-sru1.2/searchRetrieve-v1.0-os-part2-sru1.2.doc (HTML), (PDF)
- OASIS-SRU20
-
searchRetrieve: Part 3. SRU searchRetrieve Operation: APD Binding for SRU 2.0 Version 1.0, OASIS, January 2013, http://docs.oasis-open.org/search-ws/searchRetrieve/v1.0/os/part3-sru2.0/searchRetrieve-v1.0-os-part3-sru2.0.doc (HTML), (PDF)
- OASIS-CQL
-
searchRetrieve: Part 5. CQL: The Contextual Query Language version 1.0, OASIS, January 2013, http://docs.oasis-open.org/search-ws/searchRetrieve/v1.0/os/part5-cql/searchRetrieve-v1.0-os-part5-cql.doc (HTML), (PDF)
- SRU-Explain
-
searchRetrieve: Part 7. SRU Explain Operation version 1.0, OASIS, January 2013, http://docs.oasis-open.org/search-ws/searchRetrieve/v1.0/os/part7-explain/searchRetrieve-v1.0-os-part7-explain.doc (HTML), (PDF)
- SRU-Scan
-
searchRetrieve: Part 6. SRU Scan Operation version 1.0, OASIS, January 2013, http://docs.oasis-open.org/search-ws/searchRetrieve/v1.0/os/part6-scan/searchRetrieve-v1.0-os-part6-scan.doc (HTML), (PDF)
- LOC-SRU12
-
SRU Version 1.2: SRU Search/Retrieve Operation, Library of Congress, http://www.loc.gov/standards/sru/sru-1-2.html
- LOC-DIAG
-
SRU Version 1.2: SRU Diagnostics List, Library of Congress, http://www.loc.gov/standards/sru/diagnostics/diagnosticsList.html
- UD-POS
-
Universal Dependencies, Universal POS tags v2.0, https://universaldependencies.github.io/u/pos/index.html
- SAMPA
-
Dafydd Gibbon, Inge Mertins, Roger Moore (Eds.): Handbook of Multimodal and Spoken Language Systems. Resources, Terminology and Product Evaluation, Kluwer Academic Publishers, Boston MA, 2000, ISBN 0-7923-7904-7
- CLARIN-FCS-DataViews
-
CLARIN Federated Content Search (CLARIN-FCS) - Data Views, SCCTC FCS Task-Force, April 2014, https://trac.clarin.eu/wiki/FCS/Dataviews, https://github.com/clarin-eric/fcs-misc/tree/main/fcs-dataviews-1.0, https://office.clarin.eu/v/CE-2014-0317-CLARIN_FCS_Specification_DataViews_1_0-v20170613.pdf
1.4. Non-Normative References
- CQP-TUTORIAL
-
Evert et al.: The IMS Open Corpus Workbench (CWB) CQP Query Language Tutorial, CWB Version 3.0, February 2010, http://cwb.sourceforge.net/files/CQP_Tutorial/
- RFC6838
-
Media Type Specifications and Registration Procedures, IETF RFC 6838, January 2013, https://www.ietf.org/rfc/rfc6838.html
- RFC3023
-
XML Media Types, IETF RFC 3023, January 2001, https://www.ietf.org/rfc/rfc3023.html
1.5. Typographic and XML Namespace conventions
The following typographic conventions for XML fragments will be used throughout this specification:
-
<prefix:Element>An XML element with the Generic Identifier Element that is bound to an XML namespace denoted by the prefix prefix.
-
@attrAn XML attribute with the name attr.
-
stringThe literal string must be used either as element content or attribute value.
Endpoints and Clients MUST adhere to the XML-Namespaces specification. The CLARIN-FCS interface specification generally does not dictate whether XML elements should be serialized in their prefixed or non-prefixed syntax, but Endpoints MUST ensure that the correct XML namespace is used for elements and that XML namespaces are declared correctly. Clients MUST be agnostic regarding syntax for serializing the XML elements, i.e. if the prefixed or un-prefixed variant was used, and SHOULD operate solely on expanded names, i.e. pairs of namespace name and local name.
The following XML namespace names and prefixes are used throughout this specification. The column "Recommended Syntax" indicates which syntax variant SHOULD be used by the Endpoint to serialize the XML response.
| Prefix | Namespace Name | Comment | Recommended Syntax |
|---|---|---|---|
|
CLARIN-FCS Resources |
prefixed |
|
|
CLARIN-FCS Endpoint Description |
prefixed |
|
|
CLARIN-FCS Generic Hits Data View |
prefixed |
|
|
CLARIN-FCS Advanced Data View |
prefixed |
|
|
SRU Version 2.0 |
prefixed |
|
|
SRU Version 2.0 Diagnostics |
prefixed |
|
|
SRU/ZeeRex Explain |
prefixed |
|
|
SRU Version 1.2, only compatibility mode |
prefixed |
|
|
SRU Version 1.2 Diagnostics, only compatibility mode |
prefixed |
2. CLARIN-FCS Interface Specification
The CLARIN-FCS Interface Specification defines a set of capabilities, an extensible result format and a set of required operations. CLARIN-FCS is built on the SRU/CQL standard and additional functionality required for CLARIN-FCS is added through SRU/CQL’s extension mechanisms.
Specifically, the CLARIN-FCS Interface Specification consists of two parts, a set of formats, and a transport protocol. The Endpoint component is a software component that acts as a bridge between a Client and a Search Engine and passes the requests sent by the Client to the Search Engine. The Search Engine is a custom software component that allows the search of language resources in a Repository. The Endpoint implements the Transport Protocol and acts as a mediator between the CLARIN-FCS specific formats and the idiosyncrasies of Search Engines of the individual Repositories. The following figure illustrates the overall architecture.
In general, the work flow in CLARIN-FCS is as follows: a Client submits a query to an Endpoint; the Endpoint translates the query from CQL or FCS-QL to the query dialect used by the Search Engine and submits the translated query to the Search Engine; the Search Engine processes the query and generates a result set, i.e. it compiles a set of hits that match the search criterion; the Endpoint then translates the results from the Search Engine-specific result set format to the CLARIN-FCS result format and sends them to the Client.
2.1. Discovery
The Discovery step allows a Client to gather information about an Endpoint, in particular which capabilities are supported or which resources are available for searching.
2.1.1. Capabilities
A Capability defines a certain feature set that is part of CLARIN-FCS, e.g. what kind of queries are supported. Each Endpoint implements some (or all) of these Capabilities. The Endpoint will announce the capabilities it provides to allow a Client to auto-tune itself (see section Endpoint Description). Each Capability is identified by a Capability Identifier, which uses the URI syntax. The following Capabilities are defined in CLARIN-FCS:
| Name | Capability Identifier | Summary |
|---|---|---|
Basic Search |
|
Simple full-text searching |
Advanced Search |
|
Searching in structured and/or annotated data |
Endpoints MUST implement the Basic Search Capability. Endpoints MUST NOT invent custom Capability Identifiers and MUST only use the values defined above.
2.1.2. Endpoint Description
Endpoints need to provide information about their capabilities to support auto-configuration of Clients. The Endpoint Description mechanism provides the necessary facility to provide this information to the Clients. Endpoints MUST encode their capabilities using an XML format and embed this information into the SRU/CQL protocol as described in section Operation "explain". The XML fragment generated by the Endpoint for the Endpoint Description MUST be valid according to the XML schema "Endpoint-Description.xsd".
The XML fragment for Endpoint Description is encoded as an <ed:EndpointDescription> element that contains the following attributes and children:
-
one
@versionattribute (REQUIRED) on the<ed:EndpointDescription>elementThe value of the
@versionattributeMUSTbe2. -
one
<ed:Capabilities>element (REQUIRED) that contains one or more<ed:Capability>elementsThe content of the
<ed:Capability>element is a Capability Identifier that indicates the capabilities that are supported by the Endpoint. For valid values for the Capability Identifier, see section Capabilities. This listMUST NOTinclude duplicate values. -
one
<ed:SupportedDataViews>element (REQUIRED)A list of Data Views that are supported by this Endpoint. This list is composed of one or more
<ed:SupportedDataView>elements. The content of a<ed:SupportedDataView>MUSTbe the MIME type of a supported Data View, e.g.application/x-clarin-fcs-hits+xml. Each<ed:SupportedDataView>elementMUSTcarry an@idand a@delivery-policyattribute. The value of the@idattribute is later used in the <ed:Resource> element to indicate which Data View is supported by a resource (see below). EndpointsSHOULDuse the recommended short identifier for the Data View. The@delivery-policyindicates, the Endpoint’s delivery policy, for that Data View. Valid values aresend-by-defaultfor the send-by-default andneed-to-requestfor the need-to-request delivery policy.This list
MUST NOTinclude duplicate entries, i.e. no MIME type must appear more than once.The value of the
@idattributeMUST NOTcontain the characters,(comma) or;(semicolon) -
one
<ed:SupportedLayers>element (REQUIREDif Endpoint supports Advanced Search capability)A list of Layers that are generally supported by this Endpoint. This list is composed of one or more
<ed:SupportedLayer>elements. The content of a<ed:SupportedLayer>MUSTbe the identifier of a Layer (see section Layers), e.g. orth. Each<ed:SupportedLayer>elementMUSTcarry an@idand a @result-id attribute. The value of the@idattribute is later used in the <ed:Resource> element to indicate, which Layer is supported by a resource (see below). The@result-idattribute is used in the Advanced Data View (see section Advanced Data View). Each<ed:SupportedLayer>elementMAYcarry an optional@qualifierattribute. It is used as a qualifier in a FCS-QL search term in to address this specific layer.This list
MUST NOTinclude duplicate entries, i.e. no Layer with the same@result-idMIME type must appear more than once.The value of the
@idor@result-idattributeMUST NOTcontain the characters,(comma) or;(semicolon) The value of the@qualifierattributeMUST NOTcontain characters other thana-z,A-Z,0-9and-(hyphen), and the first character MUST be one ofa-zorA-Z. The<ed:SupportedLayer>elementMAYcarry an@alt-value-infoand@alt-value-info-uriattribute;@alt-value-infoSHOULDcontain a short description about the layer, e.g. the original tag set used;@alt-value-info-uriMUSTcontain a well-formed URI andSHOULDpoint to a web site with further information, e.g. about the original tag set and how the translation to FCS is done. Client, e.g. the Aggregator, can display this information together with the search result. -
one
<ed:Resources>element (REQUIRED)A list of (top-level) resources that are available, i.e. searchable, at the Endpoint. The
<ed:Resources>element contains one or more<ed:Resource>elements (see below). The EndpointMUSTdeclare at least one (top-level) resource.
The <ed:Resource> element contains a basic description of a resource that is available at the Endpoint. A resource is a searchable entity, e.g. a single corpus. The <ed:Resource> has a mandatory @pid attribute that contains persistent identifier of the resource. This value MUST be the same as the MdSelfLink of the CMDI record describing the resource. The <ed:Resource> element contains the following children:
-
one or more
<ed:Title>elements (REQUIRED)A human-readable title for the resource. A
REQUIRED@xml:langattribute indicates the language of the title. An English version of the title isREQUIRED. The list of titlesMUST NOTcontain duplicate entries for the same language. -
zero or more
<ed:Description>elements (OPTIONAL)An optional human-readable description of the resource. It
SHOULDbe at most one sentence. AREQUIRED@xml:langattribute indicates the language of the description. If supplied, an English version of the description isREQUIRED. The list of descriptionsMUST NOTcontain duplicate entries for the same language. -
zero or more
<ed:Institution>elements (OPTIONAL)An optional human-readable name for the institution of the resource. A
REQUIRED@xml:langattribute indicates the language of the institution name. If supplied, an English version of the institution name isREQUIRED. If there is no English translation available, the element with the English language should contain the original institution name. The list of institution namesMUST NOTcontain duplicate entries for the same language. -
zero or one
<ed:LandingPageURI>element (OPTIONAL)A link to a website for the resource, e.g. a landing page for a resource, i.e. a web-site that describes a corpus.
-
one
<ed:Languages>element (REQUIRED)The (relevant) languages available within the resource. The
<ed:Languages>element contains one or more<ed:Language>elements. The content of a<ed:Language>elementMUSTbe a ISO 639-3 three letter language code. This element should be repeated for all languages (relevant) available within the resource, however this listMUST NOTcontain duplicate entries. -
one
<ed:AvailableDataViews>element (REQUIRED)The Data Views that are available for the resource. The
<ed:AvailableDataViews>elementMUSTcarry a@refattribute that contains a whitespace-separated list of id values that correspond to value of the appropriate@idattribute for the<ed:SupportedDataView>elements that are referenced.In case of sub-resources, each Resource
SHOULDsupport all Data Views that are supported by the parent resource. However, every resourceMUSTdeclare all available Data Views independently, i.e. there is no implicit inheritance semantic. -
one
<ed:AvailableLayers>element (REQUIREDif Endpoint supports Advanced Search capability)The
<ed:AvailableLayers>elementMUSTcarry a@refattribute that contains a whitespace-separated list of id values that correspond to the value of the appropriate@idattribute for the<ed:SupportedLayer>elements that are referenced.In case of sub-resources, each Resource
SHOULDsupport all Layers that are supported by the parent resource. However, every resourceMUSTdeclare all available Layers independently, i.e. there is no implicit inheritance semantic. -
zero or one
<ed:Resources>element (OPTIONAL)If a resource has searchable sub-resources, the Endpoint
MUSTsupply additional finer grained resource elements, which are wrapped in a<ed:Resources>element. A sub-resource is a searchable entity within a resource, e.g. a sub-corpus.
<ed:EndpointDescription xmlns:ed="http://clarin.eu/fcs/endpoint-description" version="2">
<ed:Capabilities>
<ed:Capability>http://clarin.eu/fcs/capability/basic-search</ed:Capability>
</ed:Capabilities>
<ed:SupportedDataViews>
<ed:SupportedDataView id="hits" delivery-policy="send-by-default">application/x-clarin-fcs-hits+xml</ed:SupportedDataView>
</ed:SupportedDataViews>
<ed:Resources>
<!-- just one top-level resource at the Endpoint -->
<ed:Resource pid="http://hdl.handle.net/4711/0815">
<ed:Title xml:lang="de">Goethe Korpus</ed:Title>
<ed:Title xml:lang="en">Goethe corpus</ed:Title>
<ed:Description xml:lang="de">Das Goethe-Korpus des IDS Mannheim.</ed:Description>
<ed:Description xml:lang="en">The Goethe corpus of IDS Mannheim.</ed:Description>
<ed:LandingPageURI>http://repos.example.org/corpus1.html</ed:LandingPageURI>
<ed:Languages>
<ed:Language>deu</ed:Language>
</ed:Languages>
<ed:AvailableDataViews ref="hits" />
</ed:Resource>
</ed:Resources>
</ed:EndpointDescription>Example simple Endpoint Description shows a simple Endpoint Description for an Endpoint that only supports the Basic Search Capability and only provides the Generic Hits Data View, which is indicated by a <ed:SupportedDataView> element. This element carries an @id attribute with a value of hits, the recommended value for the short identifier, and indicates a delivery policy of send-by-default by the @delivery-policy attribute. It only provides one top-level resource identified by the persistent identifier http://hdl.handle.net/4711/0815. The resource has a title as well as a description in German and English. A landing page is located at http://repos.example.org/corpus1.html. The predominant language in the resource contents is German. Only the Generic Hits Data View is supported for this resource, because the <ed:AvailableDataViews> element only references the <ed:SupporedDataView> element with the @id with a value of hits.
<ed:EndpointDescription xmlns:ed="http://clarin.eu/fcs/endpoint-description" version="2">
<ed:Capabilities>
<ed:Capability>http://clarin.eu/fcs/capability/basic-search</ed:Capability>
</ed:Capabilities>
<ed:SupportedDataViews>
<ed:SupportedDataView id="hits" delivery-policy="send-by-default">application/x-clarin-fcs-hits+xml</ed:SupportedDataView>
<ed:SupportedDataView id="cmdi" delivery-policy="need-to-request">application/x-cmdi+xml</ed:SupportedDataView>
</ed:SupportedDataViews>
<ed:Resources>
<!-- top-level resource 1 -->
<ed:Resource pid="http://hdl.handle.net/4711/0815">
<ed:Title xml:lang="de">Goethe Korpus</ed:Title>
<ed:Title xml:lang="en">Goethe corpus</ed:Title>
<ed:Description xml:lang="de">Das Goethe-Korpus des IDS Mannheim.</ed:Description>
<ed:Description xml:lang="en">The Goethe corpus of IDS Mannheim.</ed:Description>
<ed:LandingPageURI>http://repos.example.org/corpus1.html</ed:LandingPageURI>
<ed:Languages>
<ed:Language>deu</ed:Language>
</ed:Languages>
<ed:AvailableDataViews ref="hits" />
</ed:Resource>
<!-- top-level resource 2 -->
<ed:Resource pid="http://hdl.handle.net/4711/0816">
<ed:Title xml:lang="de">Zeitungskorpus des Mannheimer Morgen</ed:Title>
<ed:Title xml:lang="en">Mannheimer Morgen newspaper corpus</ed:Title>
<ed:LandingPageURI>http://repos.example.org/corpus2.html</ed:LandingPageURI>
<ed:Languages>
<ed:Language>deu</ed:Language>
</ed:Languages>
<ed:AvailableDataViews ref="hits cmdi" />
<ed:Resources>
<!-- sub-resource 1 of top-level resource 2 -->
<ed:Resource pid="http://hdl.handle.net/4711/0816-1">
<ed:Title xml:lang="de">Zeitungskorpus des Mannheimer Morgen (vor 1990)</ed:Title>
<ed:Title xml:lang="en">Mannheimer Morgen newspaper corpus (before 1990)</ed:Title>
<ed:LandingPageURI>http://repos.example.org/corpus2.html#sub1</ed:LandingPageURI>
<ed:Languages>
<ed:Language>deu</ed:Language>
</ed:Languages>
<ed:AvailableDataViews ref="hits cmdi" />
</ed:Resource>
<!-- sub-resource 2 of top-level resource 2 -->
<ed:Resource pid="http://hdl.handle.net/4711/0816-2">
<ed:Title xml:lang="de">Zeitungskorpus des Mannheimer Morgen (nach 1990)</ed:Title>
<ed:Title xml:lang="en">Mannheimer Morgen newspaper corpus (after 1990)</ed:Title>
<ed:LandingPageURI>http://repos.example.org/corpus2.html#sub2</ed:LandingPageURI>
<ed:Languages>
<ed:Language>deu</ed:Language>
</ed:Languages>
<ed:AvailableDataViews ref="hits cmdi" />
</ed:Resource>
</ed:Resources>
</ed:Resource>
</ed:Resources>
</ed:EndpointDescription>The more complex Example CMDI Endpoint Description show an Endpoint Description for an Endpoint that, similar to Example simple Endpoint Description, supports the Basic Search capability. In addition to the Generic Hits Data View, it also supports the CMDI Data View. The delivery polices are send-by-default for the Generic Hits Data View and need-to-request for the CMDI Data View. The Endpoint has two top-level resources (identified by the persistent identifiers http://hdl.handle.net/4711/0815 and http://hdl.handle.net/4711/0816. The second top-level resource has two independently searchable sub-resources, identified by the persistent identifier http://hdl.handle.net/4711/0816-1 and http://hdl.handle.net/4711/0816-2. All resources are described using several properties, like title, description, etc. The first top-level resource provides only the Generic Hits Data View, while the other top-level resource including its children provide the Generic Hits and the CMDI Data Views.
<ed:EndpointDescription xmlns:ed="http://clarin.eu/fcs/endpoint-description" version="2">
<ed:Capabilities>
<ed:Capability>http://clarin.eu/fcs/capability/basic-search</ed:Capability>
<ed:Capability>http://clarin.eu/fcs/capability/advanced-search</ed:Capability>
</ed:Capabilities>
<ed:SupportedDataViews>
<ed:SupportedDataView id="hits" delivery-policy="send-by-default">application/x-clarin-fcs-hits+xml</ed:SupportedDataView>
<ed:SupportedDataView id="adv" delivery-policy="send-by-default">application/x-clarin-fcs-adv+xml</ed:SupportedDataView>
</ed:SupportedDataViews>
<ed:SupportedLayers>
<ed:SupportedLayer id="word" result-id="http://spraakbanken.gu.se/ns/fcs/layer/word">text</ed:SupportedLayer>
<ed:SupportedLayer id="orth" result-id="http://endpoint.example.org/Layers/orth" type="empty">orth</ed:SupportedLayer>
<ed:SupportedLayer id="lemma" result-id="http://spraakbanken.gu.se/ns/fcs/layer/lemma">lemma</ed:SupportedLayer>
<ed:SupportedLayer id="pos" result-id="http://spraakbanken.gu.se/ns/fcs/layer/pos"
alt-value-info="SUC tagset"
alt-value-info-uri="https://spraakbanken.gu.se/parole/Docs/SUC2.0-manual.pdf"
qualifier="suc">pos</ed:SupportedLayer>
<ed:SupportedLayer id="pos2" result-id="http://spraakbanken.gu.se/ns/fcs/layer/pos2"
alt-value-info="2nd tagset"
qualifier="t2">pos</ed:SupportedLayer>
</ed:SupportedLayers>
<ed:Resources>
<!-- just one top-level resource at the Endpoint -->
<ed:Resource pid="hdl:10794/suc">
<ed:Title xml:lang="sv">SUC-korpusen</ed:Title>
<ed:Title xml:lang="en">The SUC corpus</ed:Title>
<ed:Description xml:lang="sv">Stockholm-Umeå-korpusen hos Språkbanken.</ed:Description>
<ed:Description xml:lang="en">The Stockholm-Umeå corpus at Språkbanken.</ed:Description>
<ed:LandingPageURI>https://spraakbanken.gu.se/resurser/suc</ed:LandingPageURI>
<ed:Languages>
<ed:Language>swe</ed:Language>
</ed:Languages>
<ed:AvailableDataViews ref="hits adv" />
<ed:AvailableLayers ref="word lemma pos pos2" />
</ed:Resource>
</ed:Resources>
</ed:EndpointDescription>Example advanced Endpoint Description shows an Endpoint Description for an Endpoint that supports the Advanced Search capability. The <ed:SupportedDataViews> also shows support for Advanced Data View in this case. The <ed:SupportedLayers> contains the list of <ed:SupportedLayer> elements. These elements must carry an @id attribute that is referred to by an <ed:Resource> element to indicate which Data View is supported and a @result-id attribute. The @result-id attribute is used in ADV. If needed the optional @qualifier attribute is used in a FCS-QL search term to address this specific layer, e.g. pos or pos2. The attribute @alt-value-info should contain a short description about the layer. If further information is needed use the @alt-value-info-uri attribute with an well-fomed URI to point to a web site. This information could be shown by the Aggregator together with any search results. The attribute @type has a default value of value which should only be changed to empty when needed.
2.2. Searching
In the Searching step the Client performs the actual search request to a previously discovered Endpoint.
2.2.1. Basic Search
The Basic Search capability provides simple full-text search. Queries in Basic Search MUST be performed in the Contextual Query Language (OASIS-CQL). The Endpoint MUST support term-only queries. The Endpoint SHOULD support terms combined with boolean operator queries (AND and OR), including sub-queries. An Endpoint MAY also support NOT or PROX operator queries. If an Endpoint does not support a query, i.e. the used operators are not supported by the Endpoint, then it MUST return an appropriate error message using the appropriate SRU diagnostic (LOC-DIAG).
The Endpoint MUST perform the query on an annotation layer that makes the most sense for the user, i.e. the textual content for a text corpus resource or the orthographic transcription of a spoken language corpus. Endpoints SHOULD perform the query case-sensitive.
cat "cat" cat AND dog "grumpy cat" "grumpy cat" AND dog "grumpy cat" OR "lazy dog" cat AND (mouse OR "lazy dog")
|
Note
|
In CQL, a term can be a single token or a phrase, i.e. tokens separated by spaces. If a single term contains spaces, it needs to be quoted. |
|
Note
|
Endpoints MUST be able to parse all of CQL. If they don’t support a certain CQL feature, they MUST generate an appropriate error message (see section SRU/CQL). Especially, if an Endpoint only supports Basic Search, it MUST NOT silently accept queries that include CQL features besides term-only and terms combined with boolean operator queries, i.e. queries involving context sets, etc.
|
2.2.2. Advanced Search
The Advanced Search capability allows searching in annotated data that is represented in annotation layers. An annotation layer contains annotations of a specific type, e.g. lemma or part-of-speech layer. Queries can be performed across annotation layer.
CLARIN-FCS defines a set of searchable annotation layers with certain semantics and syntax. Endpoints SHOULD support as many different, of course depending on the resource type, annotation layers as possible.
2.2.2.1. Layers
Each Layer is assumed to be segmented, e.g. to allow for searching for a single lemma. However, CLARIN-FCS does not endorse a specific segmentation, i.e. the segmentation of Layers is in the domain of the Endpoint and opaque to CLARIN-FCS. CLARIN-FCS does not endorse nor assume a formal linguistic relation or formal linguistic hierarchy between two items on two different layers.
| Layer Type Identifier | Annotation Layer Description | Syntax | Examples (without quotes) |
|---|---|---|---|
|
Textual representation of resource, also the layer that is used in Basic Search |
String |
"Dog", "cat" "walking", "better" |
|
Lemmatisation |
String |
"good", "walk", "dog" |
|
Part-of-Speech annotations |
Universal POS tags |
"NOUN", "VERB", "ADJ" |
|
Orthographic transcription of (mostly) spoken resources |
String |
"dug", "cat", "wolking" |
|
Orthographic normalization of (mostly) spoken resources |
String |
"dog", "cat", "walking", "best" |
|
Phonetic transcription |
"'du:", "'vi:-d6 'ha:-b@n" |
The column Layer Type Identifier denotes the identifier for a layer. It is used in FCS-QL queries and the XML serialization for the Advanced Data View. All valid identifiers are defined in the table above, all other identifiers are reserved and MUST NOT be used. Clients and Endpoints MAY create custom Layer Type Identifiers, e.g. for testing proposed. If they do so, the custom Layer Type identifiers MUST start with the String x-, e.g. x-customLayer. The column Syntax describes the inventory of symbols that a Client MUST use with a corresponding annotation layer; the value String denotes that symbols are arbitrary Unicode Strings, i.e. no fixed inventory of symbols is defined. An Endpoint SHOULD provide an appropriate error, if a Client used an invalid value.
2.2.2.2. FCS-QL
Queries in Advanced Search MUST be performed using FCS-QL (FCS-QL Grammar). The Endpoint MUST support parsing all of FCS-QL. If an Endpoint does not support a query, i.e. the used operators or layers are not supported by the Endpoint, it MUST return an appropriate error message using the appropriate SRU diagnostic (LOC-DIAG). However, if the parameter x-fcs-rewrites-allowed is set to true, the Endpoint MAY rewrite the query with changed recall as a result.
The Endpoint MUST perform the query on the annotation layers that makes the most sense for the user, e.g. if no specific [PartofSpeech] layer is given with several layers available from the Discovery phase it should use the most generic one. Endpoints SHOULD perform the query with case sensitivity as specified in the query which by default is case sensitive.
"walking"
[token = "walking"]
"Dog" /c
[word = "Dog" /c]
[pos = "NOUN"]
[pos != "NOUN"]
[lemma = "walk"]
"blaue|grüne" [pos = "NOUN"]
"dogs" []{3,} "cats" within s
[z:pos = "ADJ"]
[z:pos = "ADJ" & q:pos = "ADJ"]
The qualifiers z in z:pos and q in q:pos SHOULD match an available qualifier attribute value in a pos-SupportedLayer in a discovered [EndpointDescripion].
|
Note
|
Endpoints supporting Advanced Search MUST be able to parse all of FCS-QL. If they don’t support a certain FCS-QL feature, they MUST generate an appropriate error message (see section SRU/CQL). If an Endpoint only supports Basic Search, it MUST NOT silently accept queries that include FCS-QL features.
|
|
Note
|
FCS-QL layer identifiers are reserved. The Endpoint MUST prepend the local prefix x- to any identifier used outside of the reserved set, e.g., x-customLayer for a local identifier customLayer.
|
2.2.3. Result Format
The Search Engine will produce a result set containing several hits as the outcome of processing a query. The Endpoint MUST serialize these hits in the CLARIN-FCS result format. Endpoints are REQUIRED to adhere to the principle that one hit MUST be serialized as one CLARIN-FCS result record and MUST NOT combine several hits in one CLARIN-FCS result record. E.g., if a query matches five different sentences within one text (= the resource), the Endpoint must serialize them as five SRU records each with one Hit each referencing the same containing Resource (see section Operation "searchRetrieve").
CLARIN-FCS uses a customized format for returning results. Resource and Resource Fragments serve as containers for hit results, which are presented in one or more Data View. The following section describes the Resource format and Data View format and section Operation "searchRetrieve" will describe how hits are embedded within SRU responses.
2.2.3.1. Resource and ResourceFragment
To encode search results, CLARIN-FCS supports two building blocks:
- Resources
-
A Resource is a searchable and addressable entity at the Endpoint, such as a text corpus or a multi-modal corpus. A resource
SHOULDbe a self-contained unit, i.e. not a single sentence in a text corpus or a time interval in an audio transcription, but rather a complete document from a text corpus or a complete audio transcription. - Resource Fragments
-
A Resource Fragment is a smaller unit in a Resource, i.e. a sentence in a text corpus or a time interval in an audio transcription.
A Resource SHOULD be the most precise unit of data that is directly addressable as a "whole". A Resource SHOULD contain a Resource Fragment, if the hit consists of just a part of the Resource unit (for example if the hit is a sentence within a large text). A Resource Fragment SHOULD be addressable within a resource, i.e. it has an offset or a resource-internal identifier. Using Resource Fragments is OPTIONAL, but Endpoints are encouraged to use them. If the Endpoint encodes a hit with a Resource Fragment, the actual hit SHOULD be encoded as a Data View within the Resource Fragment.
Endpoints SHOULD always provide a link to the resource itself, i.e. each Resource or Resource Fragment SHOULD be identified by a persistent identifier or providing a URI that is unique for the Endpoint. Even if direct linking is not possible, i.e. due to licensing issues, the Endpoints SHOULD provide a URI to link to a web-page describing the corpus or collection, including instruction on how to obtain it. Endpoints SHOULD provide links that are as specific as possible (and logical), i.e. if a sentence within a resource cannot be addressed directly, the Resource Fragment SHOULD NOT contain a persistent identifier or an URI.
If the Endpoint can provide both, a persistent identifier as well as a URI, for either Resource or Resource Fragment, then they SHOULD provide both. When working with results, Clients SHOULD prefer persistent identifiers over regular URIs.
Resource and Resource Fragment are serialized in XML and Endpoints MUST generate responses that are valid according to the XML schema "Resource.xsd". A Resource is encoded in the form of a <fcs:Resource> element, a Resource Fragment in the form of a <fcs:ResourceFragment> element. The content of a Data View is wrapped in a <fcs:DataView> element. <fcs:Resource> is the top-level element and MAY contain zero or more <fcs:DataView> elements and MAY contain zero or more <fcs:ResourceFragment> elements. A <fcs:ResourceFragment> element MUST contain one or more <fcs:DataView> elements.
The elements <fcs:Resource>, <fcs:ResourceFragment> and <fcs:DataView> MAY carry a @pid and/or a @ref attribute, which allows linking to the original data represented by the Resource, Resource Fragment, or Data View. A @pid attribute MUST contain a valid persistent identifier, a @ref MUST contain valid URI, i.e. a "plain" URI without the additional semantics of being a persistent reference. If the Endpoint cannot provide a @pid attribute for a <fcs:Resource>, they SHOULD provide a @ref attribute. Endpoint SHOULD add either a @pid or @ref attribute to either the <fcs:Resource> or the <fcs:ResourceFragment> element, if possible to both elements. Endpoints are RECOMMENDED to give @pid attributes, if they can provide them.
Endpoints MUST use the identifier http://clarin.eu/fcs/resource for the responseItemType (= content for the <sru:recordSchema> element) in SRU responses.
Endpoints MAY serialize hits as multiple Data Views, however they MUST provide the Generic Hits (HITS) Data View either encoded as a Resource Fragment (if applicable), or otherwise within the Resource (if there is no reasonable Resource Fragment). Other Data Views SHOULD be put in a place that is logical for their content (as is to be determined by the Endpoint), e.g. a metadata Data View would most likely be put directly below Resource and a Data View representing some annotation layers directly around the hit is more likely to belong within a Resource Fragment.
<fcs:Resource xmlns:fcs="http://clarin.eu/fcs/resource" pid="http://hdl.handle.net/4711/00-15">
<fcs:DataView type="application/x-clarin-fcs-hits+xml">
<!-- data view payload omitted -->
</fcs:DataView>
</fcs:Resource>Example of Generic Hits embedded in Resource shows a simple hit, which is encoded in one Data View of type Generic Hits embedded within a Resource. The type of the Data View is identified by the MIME type application/x-clarin-fcs-hits+xml. The Resource is referenceable by the persistent identifier http://hdl.handle.net/4711/08-15.
<fcs:Resource xmlns:fcs="http://clarin.eu/fcs/resource" pid="http://hdl.handle.net/4711/08-15">
<fcs:ResourceFragment>
<fcs:DataView type="application/x-clarin-fcs-hits+xml">
<!-- data view payload omitted -->
</fcs:DataView>
</fcs:ResourceFragment>
</fcs:Resource>Example of Generic Hits embedded in Resource Fragment shows a hit encoded as a Resource Fragment embedded within a Resource. The actual hit is again encoded as one Data View of type Generic Hits. The hit is not directly referenceable, but the Resource, in which the hit occurred, is referenceable by the persistent identifier http://hdl.handle.net/4711/08-15. In contrast to Example of Generic Hits embedded in Resource, the Endpoint decided to provide a "semantically richer" encoding and embedded the hit using a Resource Fragment within the Resource to indicate that the hit is a part of a larger resource, e.g. a sentence in a text document.
<fcs:Resource xmlns:fcs="http://clarin.eu/fcs/resource"
pid="http://hdl.handle.net/4711/08-15" ref="http://repos.example.org/file/text_08_15.html">
<fcs:DataView type="application/x-cmdi+xml"
pid="http://hdl.handle.net/4711/08-15-1" ref="http://repos.example.org/file/08_15_1.cmdi">
<!-- data view payload omitted -->
</fcs:DataView>
<fcs:ResourceFragment pid="http://hdl.handle.net/4711/08-15-2" ref="http://repos.example.org/file/text_08_15.html#sentence2">
<fcs:DataView type="application/x-clarin-fcs-hits+xml">
<!-- data view payload omitted -->
</fcs:DataView>
</fcs:ResourceFragment>
</fcs:Resource>The more complex Example of Generic Hits embedded in Resource Fragment with CMDI Data View is similar to Example of Generic Hits embedded in Resource Fragment, i.e. it shows a hit is encoded as one Generic Hits Data View in a Resource Fragment, which is embedded in a Resource. In contrast to Example of Generic Hits embedded in Resource Fragment, another Data View of type CMDI is embedded directly within the Resource. The Endpoint can use this type of Data View to directly provide CMDI metadata about the Resource to Clients. All entities of the Hit can be referenced by a persistent identifier and a URI. The complete Resource is referenceable by either the persistent identifier http://hdl.handle.net/4711/08-15 or the URI http://repos.example.org/file/text_08_15.html and the CMDI metadata record in the CMDI Data View is referenceable either by the persistent identifier http://hdl.handle.net/4711/08-15-1 or the URI http://repos.example.org/file/08_15_1.cmdi. The actual hit in the Resource Fragment is also directly referenceable by either the persistent identifier http://hdl.handle.net/4711/00-15-2 or the URI http://repos.example.org/file/text_08_15.html#sentence2.
2.2.3.2. Data View
A Data View serves as a container for encoding the actual search results (the data fragments relevant to search) within CLARIN-FCS. Data Views are designed to allow for different representations of results, i.e. they are deliberately kept open to allow further extensions with more supported Data View formats. This specification only defines a most basic Data View for representing search results, called Generic Hits (see below). More Data Views are defined in the supplementary specification CLARIN-FCS-DataViews.
The content of a Data View is called Payload. Each Payload is typed and the type of the Payload is recorded in the @type attribute of the <fcs:DataView> element. The Payload type is identified by a MIME type (RFC6838, RFC3023). If no existing MIME type can be used, implementers SHOULD define a proper private mime type.
The Payload of a Data View can either be deposited inline or by reference. In the case of inline, it MUST be serialized as an XML fragment below the <fcs:DataView> element. This is the preferred method for payloads that can easily be serialized in XML. Deposition by reference is meant for content that cannot easily be deposited inline, i.e. binary content (like images). In this case, the Data View MUST include a @ref or @pid attribute that links location for Clients to download the payload. This location SHOULD be openly accessible, i.e. data can be downloaded freely without any need to perform a login.
Data Views are classified into a send-by-default and a need-to-request delivery policy. In case of the send-by-default delivery policy, the Endpoint MUST send the Data View automatically, i.e. Endpoints MUST unconditionally include the Data View when they serialize a response to a search request. In the case of need-to-request, the Client must explicitly request the Endpoint to include this Data View in the response. This enables the Endpoint to not generate and serialize Data Views that are "expensive" in terms of computational power or bandwidth for every response. To request such a Data View, a Client MUST submit a comma separated list of Data View identifiers (see section Endpoint Description) in the x-fcs-dataviews extra request parameter with the searchRetrieve request. If a Client requests a Data View that is not valid for the search context, the Endpoint MUST generate a non-fatal diagnostic http://clarin.eu/fcs/diagnostic/4 ("Requested Data View not valid for this resource"). The details field of the diagnostic MUST contain the MIME type of the Data View that was not valid. If more than one requested Data View is invalid, the Endpoint MUST generate a separate non-fatal diagnostic http://clarin.eu/fcs/diagnostic/4 for each of the requested Data Views.
The description of every Data View contains a recommendation as to how the Endpoint should handle the payload delivery, i.e. if a Data View is by default considered send-by-default or need-to-request. Endpoint MAY choose to implement different policy. The relevant information which policy is implemented by an Endpoint for a specific Data View is part of the Endpoint Description (see section Endpoint Description). For each Data View, a Recommended Short Identifier is defined that Endpoint SHOULD use for an identifier of the Data View in the list of supported Data Views in the Endpoint Description.
The Generic Hits Data View is mandatory, thus all Endpoints MUST implement it and provide search results represented in the Generic Hits Data View. Endpoints MUST implement the Generic Hits Data View with the send-by-default delivery policy.
|
Note
|
The examples in the following sections show only the payload with the enclosing <fcs:DataView> element of a Data View. Of course, the Data View must be embedded either in a <fcs:Resource> or a <fcs:ResourceFragment> element. The @pid and @ref attributes have been omitted for all inline payload types.
|
Generic Hits (HITS)
Description |
The representation of the hit |
|---|---|
MIME type |
|
Payload Disposition |
inline |
Payload Delivery |
send-by-default ( |
Recommended Short Identifier |
|
XML Schema |
The Generic Hits Data View serves as the most basic agreement in CLARIN-FCS for serialization of search results and MUST be implemented by all Endpoints. In many cases, this Data View can only serve as an (lossy) approximation, because resources at Endpoints are very heterogeneous. For instance, the Generic Hits Data View is probably not the best representation for a hit result in a corpus of spoken language, but an architecture like CLARIN-FCS requires one common representation to be implemented by all Endpoints, therefore this Data View was defined. The Generic Hits Data View supports multiple markers for supplying highlighting for an individual hit, e.g. if a query contains a (boolean) conjunction, the Endpoint can use multiple markers to provide individual highlights for the matching terms. An Endpoint MUST NOT use this Data View to aggregate several hits within one resource. Each hit SHOULD be presented within the context of a complete sentence. If that is not possible due to the nature of the type of the resource, the Endpoint MUST provide an equivalent reasonable unit of context (e.g. within a phrase of an orthographic transcription of an utterance). The <hits:Hit> element within the <hits:Result> element is not enforced by the XML schema, but Endpoints are RECOMMENDED to use it. The XML fragment of the Generic Hits payload MUST be valid according to the XML schema "DataView-Hits.xsd".
<!-- potential @pid and @ref attributes omitted -->
<fcs:DataView type="application/x-clarin-fcs-hits+xml">
<hits:Result xmlns:hits="http://clarin.eu/fcs/dataview/hits">
The quick brown <hits:Hit>fox</hits:Hit> jumps over the lazy dog.
</hits:Result>
</fcs:DataView><!-- potential @pid and @ref attributes omitted -->
<fcs:DataView type="application/x-clarin-fcs-hits+xml">
<hits:Result xmlns:hits="http://clarin.eu/fcs/dataview/hits">
The quick brown <hits:Hit>fox</hits:Hit> jumps over the lazy <hits:Hit>dog</hits:Hit>.
</hits:Result>
</fcs:DataView>Advanced (ADV)
Description |
The representation of the hit for Advanced Search |
|---|---|
MIME type |
|
Payload Disposition |
inline |
Payload Delivery |
send-by-default ( |
Recommended Short Identifier |
|
XML Schema |
The Advanced (ADV) Data View serves as the natural serialization of search results for Advanced Search queries. The ADV Data View supports structured information in one or more annotation layers. The annotations are streams (ranges) over the signal in a stand-off like format with start and end offsets. The list of <Segment> elements building a stream can be of type item for character-based streams or timestamp for audio streams (granularity up to 0.001s). The Endpoint is responsible for choosing the proper offsets for the segments. The segments MUST be possible to align over all annotation layers. For character streams the recommendation is Unicode Normalization Form KC. Segments MAY also have an endpoint specific reference indicated by an URI that could be shown in the Aggregator, e.g. to open an audio player or other viewer with contents from the Search Engine. The list of <Layer> elements contains <Span> elements making references to the segments. A <Span> inherits the start and end offsets from its segments and contains the actual annotation as its content. It MAY also carry information about the original annotation value in an @alt-value attribute. The document order of the <Layer> elements define the view order in the Aggregator. Each Layer has a Layer type identifier and a Layer identifier. The Endpoint SHOULD at least return all layers that were referenced in the Advanced Search query. It MAY return more layers. The attribute @highlight is used to mark Spans as hits. Multiple hit markers are supported and the Aggregator MAY display them visually distinct. It is up to the Endpoint to decide what should be marked as a hit, but the recommendation is to mark everything referenced in the Advanced Search query.
Data |
t |
d |
a |
' |
s |
d |
e |
e |
n |
i |
g |
e |
e |
c |
h |
t |
e |
h |
||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Offset |
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
12 |
13 |
14 |
15 |
16 |
17 |
18 |
19 |
20 |
21 |
22 |
23 |
24 |
Data |
o |
o |
p |
v |
o |
o |
r |
o |
n |
s |
m |
e |
n |
s |
e |
n |
||||||||
Offset |
25 |
26 |
27 |
28 |
29 |
30 |
31 |
32 |
33 |
34 |
35 |
36 |
37 |
38 |
39 |
40 |
41 |
42 |
43 |
Offset (Start, End) |
1,1 |
3,4 |
6,7 |
9,10 |
12,16 |
18,22 |
24,27 |
29,32 |
34,36 |
38,43 |
|---|---|---|---|---|---|---|---|---|---|---|
Layer orth |
t |
da |
's |
de |
enige |
echte |
hoop |
voor |
ons |
mensen |
Layer pos |
X |
PRON |
VERB |
DET |
DET |
ADJ |
NOUN |
ADP |
PRON |
NOUN |
Layer lemma |
_ |
dat |
zijn |
de |
enig |
echt |
hoop |
voor |
ons |
mens |
Layer phonetic |
t@ |
dAz |
dAz |
d@ |
en@G@ |
Ext@ |
hop |
for |
Ons |
mEns@ |
<Advanced>
<Segments unit="items">
<Segment id="s1" start="1" end="1"
ref="http://hdl.handle.net/4711/123456789?urlappend=%3Fplay=0:173"/>
<Segment id="s2" start="3" end="4"
ref="http://hdl.handle.net/4711/123456789?urlappend=%3Fplay=173:304"/>
<Segment id="s3" start="6" end="7"
ref="http://hdl.handle.net/4711/123456789?urlappend=%3Fplay=173:304"/>
<Segment id="s4" start="9" end="10"
ref="http://hdl.handle.net/4711/123456789?urlappend=%3Fplay=304:480"/>
<Segment id="s5" start="12" end="16"
ref="http://hdl.handle.net/4711/123456789?urlappend=%3Fplay=480:1119"/>
<Segment id="s6" start="18" end="22"
ref="http://hdl.handle.net/4711/123456789?urlappend=%3Fplay=1339:1901"/>
<Segment id="s7" start="24" end="27"
ref="http://hdl.handle.net/4711/123456789?urlappend=%3Fplay=1901:2427"/>
<Segment id="s8" start="29" end="32"
ref="http://hdl.handle.net/4711/123456789?urlappend=%3Fplay=3084:3493"/>
<Segment id="s9" start="34" end="36"
ref="http://hdl.handle.net/4711/123456789?urlappend=%3Fplay=3493:3754"/>
<Segment id="s10" start="38" end="43"
ref="http://hdl.handle.net/4711/123456789?urlappend=%3Fplay=3754:4274"/>
</Segments>
<Layers>
<Layer id="http://endpoint.example.org/Layers/orth1">
<Span ref="s1">t</Span>
<Span ref="s2">da</Span>
<Span ref="s3">'s</Span>
<Span ref="s4">de</Span>
<Span ref="s5">enige</Span>
<Span ref="s6">echte</Span>
<Span ref="s7">hoop</Span>
<Span ref="s8">voor</Span>
<Span ref="s9">ons</Span>
<Span ref="s10">mensen</Span>
</Layer>
<Layer id="http://endpoint.example.org/Layers/pos1">
<Span ref="s1" alt-value="SPEC(afgebr)">X</Span>
<Span ref="s2" alt-value="VNW(aanw,pron,stan,vol,3o,ev)">PRON</Span>
<Span ref="s3" alt-value="WW(pv,tgw,ev)">VERB</Span>
<Span ref="s4" alt-value="LID(bep,stan,rest)">DET</Span>
<Span ref="s5" alt-value="VNW(onbep,det,stan,prenom,met-e,rest)">DET</Span>
<Span ref="s6" alt-value="ADJ(prenom,basis,met-e,stan)">ADJ</Span>
<Span ref="s7" alt-value="N(soort,ev,basis,zijd,stan)">NOUN</Span>
<Span ref="s8" alt-value="VZ(init)">ADP</Span>
<Span ref="s9" alt-value="VNW(pr,pron,obl,vol,1,mv)">PRON</Span>
<Span ref="s10" alt-value="N(soort,mv,basis)">NOUN</Span>
</Layer>
<Layer id="http://endpoint.example.org/Layers/lemma1">
<Span ref="s1">_</Span>
<Span ref="s2">dat</Span>
<Span ref="s3">zijn</Span>
<Span ref="s4">de</Span>
<Span ref="s5">enig</Span>
<Span ref="s6" highlight="h1">echt</Span>
<Span ref="s7" highlight="h1">hoop</Span>
<Span ref="s8">voor</Span>
<Span ref="s9">ons</Span>
<Span ref="s10">mens</Span>
</Layer>
<Layer id="http://endpoint.example.org/Layers/phon">
<Span ref="s1">t@</Span>
<Span ref="s2" highlight="h2">dAz</Span>
<Span ref="s3">dAz</Span>
<Span ref="s4">d@</Span>
<Span ref="s5">en@G@</Span>
<Span ref="s6">Ext@</Span>
<Span ref="s7">hop</Span>
<Span ref="s8">for</Span>
<Span ref="s9">Ons</Span>
<Span ref="s10">mEns@</Span>
</Layer>
</Layers>
</Advanced>2.2.4. Versioning and Extensions
2.2.4.1. Backwards Compatibility
Clients MUST be compatible to CLARIN-FCS 1.0, thus MUST implement SRU 1.2. If a Client uses CLARIN-FCS 1.0 to talk to an Endpoint, it MUST NOT use features beyond the Basic Search capability. Clients MUST implement a heuristic to automatically determine which CLARIN-FCS protocol version, i.e. which version of the SRU protocol, can be used talk an Endpoint.
Clients MUST be able to process the legacy XML namespaces:
-
http://www.loc.gov/zing/srw/for SRU response documents, and -
http://www.loc.gov/zing/srw/diagnostic/for diagnostics within SRU response documents.
which SRU 1.2 Endpoints use for serializing responses as well as the OASIS XML namespaces. CLARIN-FCS deviates from the OASIS specification OASIS-SRU-Overview and OASIS-SRU12 to ensure backwards comparability with SRU 1.2 services as they were defined by the LOC-SRU12.
Pseudo algorithm for version detection heuristic:
-
Send explain request without
versionandoperationparameter. -
Check SRU response for content of the element
<sru:explainResponse>/<sru:version>.
2.2.4.2. Endpoint Custom Extensions
Endpoints can add custom extensions, i.e. custom data, to the Result Format. This extension mechanism can for example be used to provide hints for an (XSLT/XQuery) application that works directly on CLARIN-FCS, e.g. to allow it to generate back and forward links to navigate in a result set.
An Endpoint MAY add arbitrary XML fragments to the extension hooks provided in the <fcs:Resource> element (see the XML schema for "Resource.xsd"). The XML fragment for the extension MUST use a custom XML namespace name for the extension. Endpoints MUST NOT use XML namespace names that start with the prefixes http://clarin.eu, http://www.clarin.eu/, https://clarin.eu or https://www.clarin.eu/.
A Client MUST ignore any custom extensions it does not understand and skip over these XML fragments when parsing the Endpoint’s response.
The non-normative appendix contains an example, how an extension could be implemented.
3. CLARIN-FCS to SRU/CQL binding
3.1. SRU/CQL
CLARIN-FCS Core 2.0 uses SRU 2.0 (Search/Retrieve via URL) as underlaying communication protocol. SRU specifies a general communication protocol for searching and retrieving records and CQL (Contextual Query Language) specifies extensible query language. SRU 2.0 allows using additional custom query languages. CLARIN-FCS Core 2.0 uses FCS-QL for the Advanced Search capability.
Endpoints and Clients MUST implement the SRU/CQL protocol suite as defined in OASIS-SRU-Overview, OASIS-SRU-APD, OASIS-CQL, SRU-Explain, SRU-Scan, especially with respect to:
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Data Model,
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Query Model,
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Processing Model,
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Result Set Model, and
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Diagnostics Model.
Endpoints and Clients MUST implement the APD Binding for SRU 2.0, as defined in OASIS-SRU20.
Clients MUST implement APD Binding for SRU 1.2, as defined in OASIS-SRU12.
Clients MAY also implement APD binding for version 1.1.
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Note
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when implementing SRU 1.2 Endpoints and Clients MUST behave like described in the section Backwards Compatibility.
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Endpoints or Clients MUST support CQL conformance Level 2 (as defined in OASIS-CQL, section 6), i.e. be able to parse (Endpoints) or serialize (Clients) all of CQL and respond with appropriate error messages to the search/retrieve protocol interface.
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Note
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this does not imply that Endpoints are required to support all of CQL, but rather that they are able to parse all of CQL and generate the appropriate error message, if a query includes a feature they do not support. |
Endpoints MUST generate diagnostics according to OASIS-SRU20, Appendix D for error conditions or to indicate unsupported features. Unfortunately, the OASIS specification does not provides a comprehensive list of diagnostics for CQL-related errors. Therefore, Endpoints MUST use diagnostics from LOC-DIAG, section "Diagnostics Relating to CQL" for CQL related errors.
Endpoints MUST support the HTTP GET OASIS-SRU20, Appendix B.1 and HTTP POST OASIS-SRU20, Appendix B.2 lower level protocol binding. Endpoints MAY also support the SOAP OASIS-SRU20, Appendix B.3 binding.
3.2. Operation explain
The explain operation of the SRU protocol serves to announce server capabilities and to allow clients to configure themselves automatically. This operation is used similarly.
The Endpoint MUST respond to a explain request by a proper explain response. As per SRU-Explain, the response MUST contain one <sru:record> element that contains an SRU Explain record. The <sru:recordSchema> element MUST contain the literal http://explain.z3950.org/dtd/2.0/, i.e. the official identifier for Explain records.
According to the Capabilities supported by the Endpoint the Explain record MUST contain the following elements:
- "Basic Search" Capability
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<zr:serverInfo>as defined in SRU-Explain (REQUIRED).<zr:databaseInfo>as defined in SRU-Explain (REQUIRED).<zr:schemaInfo>as defined in SRU-Explain (REQUIRED). This elementMUSTcontain an element<zr:schema>with an@identifierattribute with a value ofhttp://clarin.eu/fcs/resourceand a@nameattribute with a value offcs.<zr:configInfo>isOPTIONAL.Other capabilities may define how the
<zr:indexInfo>element is to be used, therefore it isNOT RECOMMENDEDfor Endpoints to use it in custom extensions.
To support auto-configuration in CLARIN-FCS, the Endpoint MUST provide an Endpoint Description. The Endpoint Description is included in explain response utilizing SRUs extension mechanism, i.e. by embedding an XML fragment into the <sru:extraResponseData> element. The Endpoint MUST include the Endpoint Description only if the Client performs an explain request with the extra request parameter x-fcs-endpoint-description with a value of true. If the Client performs an explain request without supplying this extra request parameter the Endpoint MUST NOT include the Endpoint Description. The format of the Endpoint Description XML fragment is defined in Endpoint Description.
The following example shows a SRU 1.2 request and response to an explain request with added extra request parameter x-fcs-endpoint-description:
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HTTP GET request: Client → Endpoint:
http://repos.example.org/fcs-endpoint?operation=explain&version=1.2&x-fcs-endpoint-description=true
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HTTP response: Endpoint → Client:
<?xml version='1.0' encoding='utf-8'?> <sru:explainResponse xmlns:sru="http://www.loc.gov/zing/srw/"> <sru:version>1.2</sru:version> <sru:record> <sru:recordSchema>http://explain.z3950.org/dtd/2.0/</sru:recordSchema> <sru:recordPacking>xml</sru:recordPacking> <sru:recordData> <zr:explain xmlns:zr="http://explain.z3950.org/dtd/2.0/"> <!-- <zr:serverInfo > is REQUIRED --> <zr:serverInfo protocol="SRU" version="1.2" transport="http"> <zr:host>repos.example.org</zr:host> <zr:port>80</zr:port> <zr:database>fcs-endpoint</zr:database> </zr:serverInfo> <!-- <zr:databaseInfo> is REQUIRED --> <zr:databaseInfo> <zr:title lang="de">Goethe Corpus</zr:title> <zr:title lang="en" primary="true">Goethe Korpus</zr:title> <zr:description lang="de">Das Goethe-Korpus des IDS Mannheim.</zr:description> <zr:description lang="en" primary="true">The Goethe corpus of IDS Mannheim.</zr:description> </zr:databaseInfo> <!-- <zr:schemaInfo> is REQUIRED --> <zr:schemaInfo> <zr:schema identifier="http://clarin.eu/fcs/resource" name="fcs"> <zr:title lang="en" primary="true">CLARIN Federated Content Search</zr:title> </zr:schema> </zr:schemaInfo> <!-- <zr:configInfo> is OPTIONAL --> <zr:configInfo> <zr:default type="numberOfRecords">250</zr:default> <zr:setting type="maximumRecords">1000</zr:setting> </zr:configInfo> </zr:explain> </sru:recordData> </sru:record> <!-- <sru:echoedExplainRequest> is OPTIONAL --> <sru:echoedExplainRequest> <sru:version>1.2</sru:version> <sru:baseUrl>http://repos.example.org/fcs-endpoint</sru:baseUrl> </sru:echoedExplainRequest> <sru:extraResponseData> <ed:EndpointDescription xmlns:ed="http://clarin.eu/fcs/endpoint-description" version="1"> <ed:Capabilities> <ed:Capability>http://clarin.eu/fcs/capability/basic-search</ed:Capability> </ed:Capabilities> <ed:SupportedDataViews> <ed:SupportedDataView id="hits" delivery-policy="send-by-default">application/x-clarin-fcs-hits+xml</ed:SupportedDataView> </ed:SupportedDataViews> <ed:Resources> <!-- just one top-level resource at the Endpoint --> <ed:Resource pid="http://hdl.handle.net/4711/0815"> <ed:Title xml:lang="de">Goethe Corpus</ed:Title> <ed:Title xml:lang="en">Goethe Korpus</ed:Title> <ed:Description xml:lang="de">Das Goethe-Korpus des IDS Mannheim.</ed:Description> <ed:Description xml:lang="en">The Goethe corpus of IDS Mannheim.</ed:Description> <ed:LandingPageURI>http://repos.example.org/corpus1.html</ed:LandingPageURI> <ed:Languages> <ed:Language>deu</ed:Language> </ed:Languages> <ed:AvailableDataViews ref="hits"/> </ed:Resource> </ed:Resources> </ed:EndpointDescription> </sru:extraResponseData> </sru:explainResponse>
And a SRU 2.0 example request and response to an explain request also with the extra request parameter x-fcs-endpoint-description:
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HTTP GET request: Client → Endpoint:
http://repos.example.org/fcs-endpoint?operation=explain&x-fcs-endpoint-description=true
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HTTP response: Endpoint → Client:
<sruResponse:explainResponse> <sruResponse:version>2.0</sruResponse:version> <sruResponse:record> <sruResponse:recordSchema>http://explain.z3950.org/dtd/2.0/</sruResponse:recordSchema> <sruResponse:recordXMLEscaping>xml</sruResponse:recordXMLEscaping> <sruResponse:recordData> <zr:explain> <zr:serverInfo protocol="SRU" version="2.0" transport="http"> <zr:host>127.0.0.1</zr:host> <zr:port>8080</zr:port> <zr:database>korp-endpoint</zr:database> </zr:serverInfo> <zr:databaseInfo> <zr:title lang="se">Språkbankens korpusar</zr:title> <zr:title lang="en" primary="true">The Språkbanken corpora</zr:title> <zr:description lang="se">Sök i Språkbankens korpusar.</zr:description> <zr:description lang="en" primary="true">Search in the Språkbanken corpora.</zr:description> <zr:author lang="en">Språkbanken (The Swedish Language Bank)</zr:author> <zr:author lang="se" primary="true">Språkbanken</zr:author> </zr:databaseInfo> <zr:indexInfo> <zr:set identifier="http://clarin.eu/fcs/resource" name="fcs"> <zr:title lang="se">Clarins innehållssökning</zr:title> <zr:title lang="en" primary="true">CLARIN Content Search</zr:title> </zr:set> <zr:index search="true" scan="false" sort="false"> <zr:title lang="en" primary="true">Words</zr:title> <zr:map primary="true"> <zr:name set="fcs">words</zr:name> </zr:map> </zr:index> </zr:indexInfo> <zr:schemaInfo> <zr:schema identifier="http://clarin.eu/fcs/resource" name="fcs"> <zr:title lang="en" primary="true">CLARIN Content Search</zr:title> </zr:schema> </zr:schemaInfo> <zr:configInfo> <zr:default type="numberOfRecords">250</zr:default> <zr:setting type="maximumRecords">1000</zr:setting> </zr:configInfo> </zr:explain> </sruResponse:recordData> </sruResponse:record> <sruResponse:echoedExplainRequest> <sruResponse:version>2.0</sruResponse:version> </sruResponse:echoedExplainRequest> <sruResponse:extraResponseData> <ed:EndpointDescription version="2"> <ed:Capabilities> <ed:Capability>http://clarin.eu/fcs/capability/basic-search</ed:Capability> <ed:Capability>http://clarin.eu/fcs/capability/advanced-search</ed:Capability> </ed:Capabilities> <ed:SupportedDataViews> <ed:SupportedDataView id="hits" delivery-policy="send-by-default">application/x-clarin-fcs-hits+xml</ed:SupportedDataView> <ed:SupportedDataView id="adv" delivery-policy="send-by-default">application/x-clarin-fcs-adv+xml</ed:SupportedDataView> </ed:SupportedDataViews> <ed:SupportedLayers> <ed:SupportedLayer id="word" result-id="http://spraakbanken.gu.se/ns/fcs/layer/word">text</ed:SupportedLayer> <ed:SupportedLayer id="lemma" result-id="http://spraakbanken.gu.se/ns/fcs/layer/lemma">lemma</ed:SupportedLayer> <ed:SupportedLayer id="pos" result-id="http://spraakbanken.gu.se/ns/fcs/layer/pos">pos</ed:SupportedLayer> </ed:SupportedLayers> <ed:Resources> <ed:Resource pid="hdl:10794/suc"> <ed:Title xml:lang="sv">SUC-korpusen</ed:Title> <ed:Title xml:lang="en">The SUC corpus</ed:Title> <ed:Description xml:lang="sv">Stockholm-Umeå-korpusen hos Språkbanken.</ed:Description> <ed:Description xml:lang="en">The Stockholm-Umeå corpus at Språkbanken.</ed:Description> <ed:LandingPageURI>https://spraakbanken.gu.se/resurser/suc</ed:LandingPageURI> <ed:Languages> <ed:Language>swe</ed:Language> </ed:Languages> <ed:AvailableDataViews ref="hits adv"/> <ed:AvailableLayers ref="word lemma pos"/> </ed:Resource> </ed:Resources> </ed:EndpointDescription> </sruResponse:extraResponseData> </sruResponse:explainResponse>
3.3. Operation scan
The scan operation of the SRU protocol is currently neither used in the Basic Search nor Advanced Search capability of CLARIN-FCS. Future capabilities may use this operation, therefore it is NOT RECOMMENDED for Endpoints to define custom extensions that use this operation.
3.4. Operation searchRetrieve
The searchRetrieve operation of the SRU protocol is used for searching in the Resources that are provided by the Endpoint. The SRU protocol defines the serialization of request and response formats in OASIS-SRU20 for SRU version 2.0 and OASIS-SRU12 for SRU version 1.2. An Endpoint MUST respond in the correct format, i.e. when Endpoint also supports SRU 1.2 and the request is issued in SRU version 1.2, the response must be encoded accordingly. For SRU 2.0 we introduce the queryType parameter to tell which query language to use. For Contextual Query Language the value is cql and for FCS-QL the value is fcs.
In SRU, search result hits are encoded down to a record level, i.e. the <sru:record> element, and SRU allows records to be serialized in various formats, so called record schemas. Endpoints MUST support the CLARIN-FCS record schema (see section Result Format) and MUST use the value http://clarin.eu/fcs/resource for the responseItemType ("record schema identifier"). Endpoints MUST represent exactly one hit within the Resource as one SRU record, i.e. <sru:record> element.
The following example shows a request and response to a searchRetrieve request with a term-only query for "cat":
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HTTP GET request: Client → Endpoint:
http://repos.example.org/fcs-endpoint?operation=searchRetrieve&version=1.2&query=cat
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HTTP response: Endpoint → Client:
<?xml version='1.0' encoding='utf-8'?> <sru:searchRetrieveResponse xmlns:sru="http://www.loc.gov/zing/srw/"> <sru:version>1.2</sru:version> <sru:numberOfRecords>6</sru:numberOfRecords> <sru:records> <sru:record> <sru:recordSchema>http://clarin.eu/fcs/resource</sru:recordSchema> <sru:recordPacking>xml</sru:recordPacking> <sru:recordData> <fcs:Resource xmlns:fcs="http://clarin.eu/fcs/resource" pid="http://hdl.handle.net/4711/08-15"> <fcs:ResourceFragment> <fcs:DataView type="application/x-clarin-fcs-hits+xml"> <hits:Result xmlns:hits="http://clarin.eu/fcs/dataview/hits"> The quick brown <hits:Hit>cat</hits:Hit> jumps over the lazy dog. </hits:Result> </fcs:DataView> </fcs:ResourceFragment> </fcs:Resource> </sru:recordData> <sru:recordPosition>1</sru:recordPosition> </sru:record> <!-- more <sru:records> omitted for brevity --> </sru:records> <!-- <sru:echoedSearchRetrieveRequest> is OPTIONAL --> <sru:echoedSearchRetrieveRequest> <sru:version>1.2</sru:version> <sru:query>cat</sru:query> <sru:xQuery xmlns="http://www.loc.gov/zing/cql/xcql/"> <searchClause> <index>cql.serverChoice</index> <relation> <value>=</value> </relation> <term>cat</term> </searchClause> </sru:xQuery> <sru:startRecord>1</sru:startRecord> <sru:baseUrl>http://repos.example.org/fcs-endpoint</sru:baseUrl> </sru:echoedSearchRetrieveRequest> </sru:searchRetrieveResponse>
Moving to SRU 2.0 have the introduced queryType parameter. The same query as seen with SRU 1.2 above would then become:
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HTTP GET request: Client → Endpoint:
http://repos.example.org/fcs-endpoint?operation=searchRetrieve&queryType=cql&query=%22anv%C3%A4ndning%22
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HTTP response: Endpoint → Client:
<?xml version='1.0' encoding='utf-8'?> <sruResponse:searchRetrieveResponse> <sruResponse:version>2.0</sruResponse:version> <sruResponse:numberOfRecords>33260</sruResponse:numberOfRecords> <sruResponse:records> <sruResponse:record> <sruResponse:recordSchema>http://clarin.eu/fcs/resource</sruResponse:recordSchema> <sruResponse:recordXMLEscaping>xml</sruResponse:recordXMLEscaping> <sruResponse:recordData> <fcs:Resource pid="ABOUNDERRATTELSER2012-32245"> <fcs:ResourceFragment> <fcs:DataView type="application/x-clarin-fcs-hits+xml"> <hits:Result>Youtube-videon har väckt debatt om polisernas <hits:Hit>användning</hits:Hit> av våld .</hits:Result> </fcs:DataView> </fcs:ResourceFragment> </fcs:Resource> </sruResponse:recordData> <sruResponse:recordPosition>1</sruResponse:recordPosition> </sruResponse:record> <!-- 249 records not shown --> </sruResponse:records> <sruResponse:nextRecordPosition>251</sruResponse:nextRecordPosition> <sruResponse:echoedSearchRetrieveRequest> <sruResponse:version>2.0</sruResponse:version> <sruResponse:query>"användning"</sruResponse:query> <sruResponse:xQuery> <searchClause> <index>cql.serverChoice</index> <relation><value>=</value></relation> <term>användning</term> </searchClause> </sruResponse:xQuery> <sruResponse:startRecord>1</sruResponse:startRecord> </sruResponse:echoedSearchRetrieveRequest> <sruResponse:resultCountPrecision>info:srw/vocabulary/resultCountPrecision/1/exact</sruResponse:resultCountPrecision> </sruResponse:searchRetrieveResponse>
Using FCS-QL using queryType with value fcs we get a request and response to the searchRetrieve request with queryType fcs and query [word = "användning"]:
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HTTP GET request: Client → Endpoint:
http://repos.example.org/fcs-endpoint?operation=searchRetrieve&queryType=fcs&query=%5bword%3d%22anv%C3%A4ndning%22%5d&x-cmd-resource-info=true
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HTTP response: Endpoint → Client:
<?xml version='1.0' encoding='utf-8'?> <sruResponse:searchRetrieveResponse> <sruResponse:version>2.0</sruResponse:version> <sruResponse:numberOfRecords>33260</sruResponse:numberOfRecords> <sruResponse:records> <sruResponse:record> <sruResponse:recordSchema>http://clarin.eu/fcs/resource</sruResponse:recordSchema> <sruResponse:recordXMLEscaping>xml</sruResponse:recordXMLEscaping> <sruResponse:recordData> <fcs:Resource pid="ABOUNDERRATTELSER2012-32245"> <fcs:ResourceFragment> <fcs:DataView type="application/x-clarin-fcs-hits+xml"> <hits:Result>Youtube-videon har väckt debatt om polisernas <hits:Hit>användning</hits:Hit> av våld .</hits:Result> </fcs:DataView> <fcs:DataView type="application/x-clarin-fcs-adv+xml"> <adv:Advanced unit="item"> <adv:Segments> <adv:Segment id="s1" start="1" end="14"/> <adv:Segment id="s2" start="16" end="18"/> <adv:Segment id="s3" start="20" end="24"/> <adv:Segment id="s4" start="26" end="31"/> <adv:Segment id="s5" start="33" end="34"/> <adv:Segment id="s6" start="36" end="45"/> <adv:Segment id="s7" start="47" end="56"/> <adv:Segment id="s8" start="58" end="59"/> <adv:Segment id="s9" start="61" end="64"/> <adv:Segment id="sa" start="66" end="66"/> </adv:Segments> <adv:Layers> <adv:Layer id="http://spraakbanken.gu.se/ns/fcs/layer/lemma"> <adv:Span ref="s1">|</adv:Span> <adv:Span ref="s2">|ha|</adv:Span> <adv:Span ref="s3">|väcka|</adv:Span> <adv:Span ref="s4">|debatt|</adv:Span> <adv:Span ref="s5">|om|</adv:Span> <adv:Span ref="s6">|polis|</adv:Span> <adv:Span ref="s7" highlight="h1">|användning|</adv:Span> <adv:Span ref="s8">|av|</adv:Span> <adv:Span ref="s9">|våld|</adv:Span> <adv:Span ref="sa">|</adv:Span> </adv:Layer> <adv:Layer id="http://spraakbanken.gu.se/ns/fcs/layer/word"> <adv:Span ref="s1">Youtube-videon</adv:Span> <adv:Span ref="s2">har</adv:Span> <adv:Span ref="s3">väckt</adv:Span> <adv:Span ref="s4">debatt</adv:Span> <adv:Span ref="s5">om</adv:Span> <adv:Span ref="s6">polisernas</adv:Span> <adv:Span ref="s7" highlight="h1">användning</adv:Span> <adv:Span ref="s8">av</adv:Span> <adv:Span ref="s9">våld</adv:Span> <adv:Span ref="sa">.</adv:Span> </adv:Layer> <adv:Layer id="http://spraakbanken.gu.se/ns/fcs/layer/pos"> <adv:Span ref="s1">PROPN</adv:Span> <adv:Span ref="s2">VERB</adv:Span> <adv:Span ref="s3">VERB</adv:Span> <adv:Span ref="s4">NOUN</adv:Span> <adv:Span ref="s5">ADP</adv:Span> <adv:Span ref="s6">NOUN</adv:Span> <adv:Span ref="s7" highlight="h1">NOUN</adv:Span> <adv:Span ref="s8">ADP</adv:Span> <adv:Span ref="s9">NOUN</adv:Span> <adv:Span ref="sa">PUNCT</adv:Span> </adv:Layer> </adv:Layers> </adv:Advanced> </fcs:DataView> </fcs:ResourceFragment> </fcs:Resource> </sruResponse:recordData> <sruResponse:recordPosition>1</sruResponse:recordPosition> </sruResponse:record> <!-- 249 records not shown --> </sruResponse:records> <sruResponse:nextRecordPosition>251</sruResponse:nextRecordPosition> <sruResponse:echoedSearchRetrieveRequest> <sruResponse:version>2.0</sruResponse:version> <sruResponse:startRecord>1</sruResponse:startRecord> </sruResponse:echoedSearchRetrieveRequest> <sruResponse:resultCountPrecision>info:srw/vocabulary/resultCountPrecision/1/exact</sruResponse:resultCountPrecision> </sruResponse:searchRetrieveResponse>
In general, as you can se from both the SRU 1.2 and SRU 2.0 examples above, the Endpoint is REQUIRED to accept an unrestricted search and SHOULD perform the search operation on all Resources that are available at the Endpoint. If that is for some reason not feasible, e.g. performing an unrestricted search would allocate too many resources, the Endpoint MAY independently restrict the search to a scope that it can handle. If it does so, it MUST issue a non-fatal diagnostics http://clarin.eu/fcs/diagnostic/2 ("Resource set too large. Query context automatically adjusted."). The details field of diagnostics MUST contain the persistent identifier of the resources to which the query scope was limited to. If the Endpoint limits the query scope to more than one resource, it MUST generate a separate non-fatal diagnostic http://clarin.eu/fcs/diagnostic/2 for each of the resources.
The Client can request the Endpoint to restrict the search to a sub-resource of these Resources. In this case, the Client MUST pass a comma-separated list of persistent identifiers in the x-fcs-context extra request parameter of the searchRetrieve request. The Endpoint MUST then restrict the search to those Resources, which are identified by the persistent identifiers passed by the Client. If a Client requests too many resources for the Endpoint to handle with x-fcs-context, the Endpoint MAY issue a fatal diagnostic http://clarin.eu/fcs/diagnostic/3 ("Resource set too large. Cannot perform Query.") and terminate processing. Alternatively, the Endpoint MAY also automatically adjust the scope and issue a non-fatal diagnostic http://clarin.eu/fcs/diagnostic/2 (see above). And Endpoint MUST NOT issue a http://clarin.eu/fcs/diagnostic/3 diagnostic in response to a request, if a Client performed the request without the x-fcs-context extra request parameter.
The Client can extract all valid persistent identifiers from the @pid attribute of the <ed:Resource> element, obtained by the explain request (see section Operation "explain" and section Endpoint Description). The list of persistent identifiers can get extensive, but a Client can use the HTTP POST method instead of HTTP GET method for submitting the request.
For example, to restrict the search to the Resource with the persistent identifier http://hdl.handle.net/4711/0815 the Client MUST issue the following request:
http://repos.example.org/fcs-endpoint?operation=searchRetrieve&version=1.2&query=cat&x-fcs-context=http://hdl.handle.net/4711/0815
To restrict the search to the Resources with the persistent identifier http://hdl.handle.net/4711/0815 and http://hdl.handle.net/4711/0816-2 the Client MUST issue the following request:
http://repos.example.org/fcs-endpoint?operation=searchRetrieve&version=1.2&query=cat&x-fcs-context=http://hdl.handle.net/4711/0815,http://hdl.handle.net/4711/0816-2
If an invalid persistent identifier is passed by the Client, the Endpoint MUST issue a http://clarin.eu/fcs/diagnostic/1 diagnostic, i.e. add the appropriate XML fragment to the <sru:diagnostics> element of the response. The Endpoint MAY treat this condition as fatal, i.e. just issue the diagnostic and perform no search, or it MAY treat it as non-fatal and perform the search.
If a Client wants to request one or more Data Views that are handled by Endpoint with the need-to-request delivery policy, it MUST pass a comma-separated list of Data View identifier in the x-fcs-dataviews extra request parameter of the searchRetrieve request. A Client can extract valid values for the Data View identifiers from the @id attribute of the <ed:SupportedDataView> elements in the Endpoint Description of the Endpoint (see section explain and section Endpoint Description).
For example, to request the CMDI Data View from an Endpoint that has an Endpoint Description, as described in Example of simple Endpoint Description with optional CMDI Data View, a Client would need to use the Data View identifier cmdi and submit the following request:
http://repos.example.org/fcs-endpoint?operation=searchRetrieve&version=1.2&query=cat&x-fcs-dataviews=cmdi
If an invalid Data View identifier is passed by the Client, the Endpoint MUST issue a http://clarin.eu/fcs/diagnostic/4 diagnostic, i.e. add the appropriate XML fragment to the <sru:diagnostics> element of the response. The Endpoint MAY treat this condition as fatal, i.e. simply issue the diagnostic and perform no search, or it MAY treat it a non-fatal and perform the search.
A. Normative Appendix
A.1. List of extra request parameters
The following extra request parameters are used in CLARIN-FCS. The column SRU operations lists the SRU operation, for which this extra request parameter is to be used. Clients MUST NOT use the parameter for an operation that is not listed in this column. However, if a Client sends an invalid parameter, an Endpoint SHOULD issue a fatal diagnostic "Unsupported Parameter" (info:srw/diagnostic/1/8) and stop processing the request. Alternatively, an Endpoint MAY silently ignore the invalid parameter.
| Parameter Name | SRU operations | Allowed values | Description |
|---|---|---|---|
|
explain |
|
If the parameter is given (with the value |
|
searchRetrieve |
A comma-separated list of persistent identifiers |
The Endpoint |
|
searchRetrieve |
A comma-separated list of Data View identifiers |
The Endpoint |
|
searchRetrieve |
|
If the parameter is given (with the value |
For SRU 2.0 the request parameter queryType MUST be used unless the query language is CQL which is the default. For using FCS-QL the value MUST be fcs.
A.2. List of diagnostics
Apart from the SRU diagnostics defined in OASIS-SRU12, Appendix C and LOC-DIAG, the following diagnostics are used in CLARIN-FCS. The column "Details Format" specifies what SHOULD be returned in the details field. If this column is blank, the format is "undefined" and the Endpoint MAY return whatever it feels appropriate, including nothing. The column "Impact" specifies, if the endpoint should continue ("non-fatal") or should stop ("fatal") processing.
| Identifier URI | Description | Details Format | Impact | Note |
|---|---|---|---|---|
Persistent identifier passed by the Client for restricting the search is invalid. |
The offending persistent identifier. |
non-fatal |
If more than one invalid persistent identifiers were submitted by the Client, the Endpoint |
|
Resource set too large. Query context automatically adjusted. |
The persistent identifier of the resource to which the query context was adjusted. |
non-fatal |
If an Endpoint limited the query context to more than one resource, it |
|
Resource set too large. Cannot perform Query. |
fatal |
|||
Requested Data View not valid for this resource. |
The Data View MIME type. |
non-fatal |
If more than one invalid Data View was requested, the Endpoint |
|
General query syntax error. |
Detailed error message why the query could not be parsed. |
fatal |
Endpoints |
|
Query too complex. Cannot perform Query. |
Details why could not be performed, e.g. unsupported layer or unsupported combination of operators. |
fatal |
Endpoints |
|
Query was rewritten. |
Details how the query was rewritten. |
non-fatal |
Endpoints |
|
General processing hint. |
E.g. "No matches, because layer 'XY' is not available in your selection of resources" |
non-fatal |
Endpoints |
A.3. CLARIN FCS-QL Grammar Specification
The version of the CLARIN FCS-QL is tied to the FCS Core version starting with version 2.0.
FCS-QL was developed to bridge the extension of powerfulness in searching, familiarity of query language and ease of use. The grammar specification for the FCS-QL is heavily based on Poliqarp but also with inspiration from other query languages' grammars. Building on the annotation layer metaphor with positional and structural attributes. Positional attributes can be seen as key-value pairs. Structural attributes can also have key-value pairs attached. Structural attributes themselves have the restrictions to be non-overlapping and non-recursive. The positional attributes depend on tokenization or segmentation of some kind being performed to produce tokens. A token is thus a subjective unit defined by a Repository manager and might vary in the same way values in other layers can.
An unqualified or qualified "attribute" denotes the annotation layer to be used, e.g. unqualified "word", "lemma", "pos" or qualified "ssts:pos". The default attribute is "text" for compatibility with FCS 1.0 where simple wordforms in a pair of single or double quotes can be matched. Qualifiers and other identifiers MUST start with a character a-z or A-Z.
Character literals are unescaped to Unicode Normalization Form C (NFC). Regular expressions are passed on as such for interpretation by the Endpoint.
Tokens are limited by [ and ] except for when using default attribute "text". Within a token disjunctive or conjunctive positional attribute expressions referring any layer can be joined. These can also be grouped by ( and ). Token sequences address consecutive tokens unless matchall, i.e. [] and quantifiers are used.
A.3.1. FCS-QL EBNF
[1] query ::= main-query within-part?
[2] main-query ::= simple-query
| simple-query "|" main-query /* or */
| simple-query main-query /* sequence */
| simple-query quantifier /* quantification */
[3] simple-query ::= '(' main_query ')' /* grouping */
| implicit-query
| segment-query
[4] implicit-query ::= flagged-regexp
[5] segment-query ::= "[" expression? "]"
[6] within-part ::= simple-within-part
[7] simple-within-part ::= "within" simple-within-scope
[8] simple-within-scope ::= "sentence"
| "s"
| "utterance"
| "u"
| "paragraph"
| "p"
| "turn"
| "t"
| "text"
| "session"
[9] expression ::= basic-expression
| expression "|" expression /* or */
| expression "&" expression /* and */
[10] basic-expression ::= '(' expression ')' /* grouping */
| "!" expression /* not */
| attribute operator flagged-regexp
[11] operator ::= "=" /* equals */
| "!=" /* non-equals */
[12] quantifier ::= "+" /* one-or-more */
| "*" /* zero-or-more */
| "?" /* zero-or-one */
| "{" integer "}" /* exactly n-times */
| "{" integer? "," integer "}" /* at most */
| "{" integer "," integer? "}" /* min-max */
[13] flagged-regexp ::= regexp
| regexp "/" regexp-flag+
[14] regexp-flag ::= "i" /* case-insensitive; Poliqarp/Perl compat */
| "I" /* case-sensitive; Poliqarp compat */
| "c" /* case-insensitive, CQP compat */
| "C" /* case-sensitive */
| "l" /* literal matching, CQP compat*/
| "d" /* diacritic agnostic matching, CQP compat */
[15] regexp ::= quoted-string
[16] attribute ::= simple-attribute
| qualified-attribute
[17] simple-attribute ::= identifier
[18] qualified-attribute ::= identifier ":" identifier
[19] identifier ::= identifier-first-char identifier-char*
[20] identifier-first-char ::= [a-zA-Z]
[21] identifier-char ::= [a-zA-Z0-9\-]
[22] integer ::= [0-9]+
[23] quoted-string ::= "'" (char | ws)* "'" /* single-quotes */
| """ (char | ws)* """ /* double-quotes */
[24] char ::= <any unicode codepoint excluding whitespace codepoints>
| "\" escaped-char
[25] ws ::= <any whitespace codepoint>
[26] escaped-char ::= "\" /* backslash (\) */
| "'" /* single quote (') */
| """ /* double quote (") */
| "n" /* generic newline, i.e "\n", "\r", etc */
| "t" /* character tabulation (U+0009) */
| '.' /* regex: dot (= any character) */
| '^' /* regex: caret (= beginning of string) */
| '$' /* regex: dollar (= end of string) */
| '*' /* regex: asterisk (= zero or more) */
| '+' /* regex: plus (= one or more) */
| '?' /* regex: question mark (= zero or one) */
| '(' /* regex: opening parenthesis */
| ')' /* regex: closing parenthesis */
| '{' /* regex: opening curly brace */
| '[' /* regex: opening square bracket */
| '|' /* regex: vertical bar */
| "x" hex hex /* Unicode codepoint with hex value hh */
| "u" hex hex hex hex /* Unicode codepoint with hex value hhhh */
| "U" hex hex hex hex hex hex hex hex /* Unicode codepoint with hex value hhhhhhhh */
[27] hex ::= [0-9a-fA-F]A.3.2. Notes
-
"simple-within-scope": possible values for scope
-
"sentence", "s", "utterance", "u": denote a matching scope of something like a sentence or utterance. provides compatibility with FCS 1.0 ("Generic Hits", "Each hit SHOULD be presented within the context of a complete sentence.")
-
"paragraph" | "p" | "turn" | "t": denote the next larger unit, e.g. something like a paragraph
-
"text" | "session": something like a whole document
-
-
[25]and[26]"any $SOMETING codepoint" are a pain to get easily done in at least ANTLR and JavaCC. Especially in combination with[27] -
regex are not defined/guarded by this grammar
B. Non-normative Appendix
B.1. Syntax variant for Handle system Persistent Identifier URIs
Persistent Identifiers from the Handle system are defined in two syntax variants: a regular URI format for the Handle protocol, i.e. with a hdl: prefix, or actionable URIs with a http://hdl.handle.net/ prefix. Generally, CLARIN software should support both syntax variants, therefore the CLARIN-FCS Interface Specification does not endorse a specific syntax variant. However, Endpoints are recommended to use the actionable syntax variant.
B.2. Referring to an Endpoint from a CMDI record
Centers are encouraged to provide links to their CLARIN-FCS Endpoints in the metadata records for their resources. Other services, like the VLO, can use this information for automatically configuring an Aggregator for searching resources at the Endpoint. To refer to an Endpoint, a <cmdi:ResourceProxy> element with child-element <cmdi:ResourceType> set to the value SearchService and a @mimetype attribute with a value of application/sru+xml need to be added to the CMDI record. The content of the <cmdi:ResourceRef> element must contain a URI that points to the Endpoint web service.
<cmdi:CMD xmlns:cmdi="http://www.clarin.eu/cmd/" CMDVersion="1.1">
<cmdi:Header>
<!-- ... -->
<cmdi:MdSelfLink>http://hdl.handle.net/4711/0815</cmdi:MdSelfLink>
<!-- ... -->
</cmdi:Header>
<cmdi:Resources>
<cmdi:ResourceProxyList>
<!-- ... -->
<cmdi:ResourceProxy id="r4711">
<cmdi:ResourceType mimetype="application/sru+xml">SearchService</cmdi:ResourceType>
<cmdi:ResourceRef>http://repos.example.org/fcs-endpoint</cmdi:ResourceRef>
</cmdi:ResourceProxy>
<!-- ... -->
</cmdi:ResourceProxyList>
</cmdi:Resources>
<!-- ... -->
</cmdi:CMD>B.3. Endpoint custom extensions
The CLARIN-FCS protocol specification allows Endpoints to add custom data to their responses, e.g. to provide hints to an (XSLT/XQuery) application that works directly on CLARIN-FCS. It could use the custom data to generate back and forward links for a GUI to navigate in a result set.
The following example illustrates how extensions can be embedded into the Result Format:
<fcs:Resource xmlns:fcs="http://clarin.eu/fcs/resource" pid="http://hdl.handle.net/4711/0815">
<fcs:DataView type="application/x-clarin-fcs-hits+xml">
<hits:Result xmlns:hits="http://clarin.eu/fcs/dataview/hits">
The quick brown <hits:Hit>fox</hits:Hit> jumps over the lazy <hits:Hit>dog</hits:Hit>.
</hits:Result>
</fcs:DataView>
<!--
NOTE: this is purely fictional and only serves to demonstrate how
to add custom extensions to the result representation
within CLARIN-FCS.
-->
<!--
Example 1: a hypothetical Endpoint extension for navigation in a result
set: it basically provides a set of hrefs that a GUI can convert into
navigation buttions.
-->
<nav:navigation xmlns:nav="http://repos.example.org/navigation">
<nav:curr href="http://repos.example.org/resultset/4711/4611" />
<nav:prev href="http://repos.example.org/resultset/4711/4610" />
<nav:next href="http://repos.example.org/resultset/4711/4612" />
</nav:navigation>
<!--
Example 2: a hypothetical Endpoint extension for directly referencing parent
resources: it basically provides a link to the parent resource that can be
exploited by a GUI (e.g. build on XSLT/XQuery).
-->
<parent:Parent xmlns:parent="http://repos.example.org/parent"
ref="http://repos.example.org/path/to/parent/1235.cmdi" />
</fcs:Resource>B.4. Endpoint highlight hints for repositories
An Aggregator can use the @ref attributes of the <fcs:Resource>, <fcs:ResourceFragment> or <fcs:DataView> elements to provide a link for the user to directly jump to the resource at a Repository. To support hit highlighting, an Endpoint can augment the URI in the @ref attribute with query parameters to implement hit highlighting in the Repository.
In the following example, the URI http://repos.example.org/resource.cgi/<pid> is a CGI script that displays a given resource at the Repository in HTML format and uses the highlight query parameter to add highlights to the resource. Of course, it’s up to the Endpoint and the Repository, if and how they implement such a feature.
<fcs:Resource xmlns:fcs="http://clarin.eu/fcs/resource" pid="http://hdl.handle.net/4711/0815">
<fcs:DataView type="application/x-clarin-fcs-hits+xml" ref="http://repos.example.org/resource.cgi/4711/0815?highlight=fox">
<hits:Result xmlns:hits="http://clarin.eu/fcs/dataview/hits">
The quick brown <hits:Hit>fox</hits:Hit> jumps over the lazy dog.
</hits:Result>
</fcs:DataView>
</fcs:Resource>Changelog
2024-09-04 — Add EndpointDescription > Resource > Institution element
-
Add new optional
<ed:Institution>element to further describe `<ed:Resource>`s in the Endpoint Description. -
Proofing.
2024-04-10 — Static Github Pages with builds from specification sources
2023-06-29 — Fix Typo
2023-06-12 — Conversion to AsciiDoc and Migration of specification documents to Github
-
Convert specification documents for FCS Core 2.0, Core 1.0, DataView and AAI to AsciiDoc
-
Migrate from CLARIN Trac to CLARIN Github
-
Add Github Actions workflow to automate build process
2022-08-03 — Final version on Trac
-
Fixes of typos, broken references, EBNF
-
Reformatting XML examples
-
Update Advanced Data View example, Segment end index is inclusive
2018-12-04 — SCCTC approved specification
-
Reformatting
-
Proofing, update language and examples
2017-06-16 — Specification candidate for approval by SCCTC
-
Proofing, reformulations
-
Add SRU 2.0 examples