update documentation on text indices

README.md

@@ -32,11 +32,15 @@ Log messages are written exclusively through the `stdout` and `stderr` output st
 
 ## RDF datasets
 
+### Notes on text indexing
+
+The datasets are configured to support [Jena's full text search](https://jena.apache.org/documentation/query/text-query.html) via Lucene indices. Considering triples that build an RDF graph, the string literal objects for certain predicates are indexed and made available for a text search. This means there is a text index for each predicate. Moreover, different indices can be combined at query time via a [property list](https://jena.apache.org/documentation/query/text-query.html#lists-of-indexed-properties).
+
 ### _dalia_ dataset
 
 This dataset contains the DALIA knowledge graph with information on learning resources and communities. It is initialized with RDF data from the `/dalia_data` directory with data initially provided by the [`download-dalia-data-job` CI job](https://git.rwth-aachen.de/dalia/backend/fuseki/-/blob/main/.gitlab-ci.yml?ref_type=heads#L5) before building the Docker image.
 
-Endpoints:
+**Endpoints:**
 * `/dalia/`: SPARQL, SPARUL and GSP (read+write)
 * `/dalia/query`: SPARQL
 * `/dalia/sparql`: SPARQL
@@ -44,7 +48,23 @@ Endpoints:
 * `/dalia/update`: SPARUL
 * `/dalia/data`: GSP (read+write)
 
-Text indexing: See [issue #2](https://git.rwth-aachen.de/dalia/backend/fuseki/-/issues/2).
+**Text indexing:**
+* indexed predicates and index names:
+
+| Predicate             | Index name           | Use                                                  |
+|-----------------------|----------------------|------------------------------------------------------|
+| `dcterms:title`       | `dctermsTitle`       | learning resource title, community title             |
+| `dcterms:description` | `dctermsDescription` | learning resource description, community description |
+| `fabio:hasSubtitle`   | `fabioHasSubtitle`   | learning resource subtitle                           |
+| `schema:keywords`     | `schemaKeywords`     | learning resource keywords                           |
+| `schema:name`         | `schemaName`         | organization author name                             |
+| `schema:familyName`   | `schemaFamilyName`   | person author name                                   |
+| `schema:givenName`    | `schemaGivenName`    | person author name                                   |
+
+* combined indices (property lists):
+  * `dt:learningResourceTexts`: `dcterms:title`, `dcterms:description`, `fabio:hasSubtitle`, `schema:keywords`, `schema:name`, `schema:familyName`, `schema:givenName`
+  * `dt:communityTexts`: `dcterms:title`, `dcterms:description`
+  * namespace `dt`: `http://dalia.education/text#`
 
 ### _ontologies_ dataset
 
@@ -52,13 +72,27 @@ This read-only dataset contains third-party ontologies and vocabularies that the
 
 Loaded ontologies and vocabularies: See [issue #1](https://git.rwth-aachen.de/dalia/backend/fuseki/-/issues/1).
 
-Endpoints:
+**Endpoints:**
 * `/ontologies/`: SPARQL and GSP (read)
 * `/ontologies/query`: SPARQL
 * `/ontologies/sparql`: SPARQL
 * `/ontologies/get`: GSP (read)
 
-Text indexing: See [issue #3](https://git.rwth-aachen.de/dalia/backend/fuseki/-/issues/3).
+**Text indexing:**
+* indexed predicates and index names:
+
+| Predicate                              | Index name              | Use                                                                           |
+|----------------------------------------|-------------------------|-------------------------------------------------------------------------------|
+| `rdfs:label`                           | `rdfsLabel`             | labels                                                                        |
+| `skos-last-call:prefLabel`<sup>1</sup> | `skosLastCallPrefLabel` | labels of languages ([Lexvo](http://www.lexvo.org/linkeddata/resources.html)) |
+| `spdx:licenseId`                       | `spdxLicenseId`         | SPDX: license ID                                                              |
+| `spdx:name`                            | `spdxName`              | SPDX: license full name                                                       |
+| `spdx:licenseText`                     | `spdxLicenseText`       | SPDX: license text                                                            |
+<sup>1</sup> Namespace `skos-last-call` is `http://www.w3.org/2008/05/skos#`. It is different from the [standard SKOS namespace](http://www.w3.org/2004/02/skos/core#).
+
+* combined indices (property lists):
+  * `dt:spdxLicensesTexts`: `spdx:licenseId`, `spdx:name`, `spdx:licenseText`
+  * namespace `dt`: `http://dalia.education/text#`
 
 ## Maintenance tasks