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- Agrovoc (agricultural concepts)
- DBpedia (general knowledge)
- FAST (general subject headers from OCLC, derived from LoC subject headers)
- GeoNames (places in the real world)
- Getty (content relating to artistic works)
- AAT (concepts)
- ULAN (persons and organizations)
- TGN (places)
- Library of Congress
- Genre
- Name
- Subject
- MeSH (NLM medical subject headings)
- NALT (National Agricultural Library Thesaurus)
- VIAF (authority cross-walks)
All of these services are available at http://services.ld4l.org/ld4l_services/index.jsp.
Request Parameterization
To simplify both the creation of new services and the understanding by developers of applications consuming these services, we standardized the parameters accepted by the various services as much as possible:
- query - the string containing the term(s) on which to search. Note that the Lucene tag library supports 'or'ing discrete terms (the default) or 'and'ing them (where each term in the query must appear), as well as explicit and and or boolean operators (required)
- maxRecords - the maximum number of entity URIs to return (optional)
- startRecord - the position in the result list to begin returning records (this used with maxRecords allows for result pagination) (optional)
- entity - where relevant for a given authority source (e.g., DBpedia), the class of the entity URIs to be returned (optional)
Hence the following query - http://services.ld4l.org/ld4l_services/getty_batch.jsp?query=Picasso&maxRecords=10&entity=Person - will return the triples relevant to 10 entities of class Person (i.e., from the Getty ULAN authority) where the word Picasso appears. Note that the actual number of triples return can vary widely due to differences in coverage between entities, even within a single authority source.
Technology Stack
The overall architecture was implemented entirely with open source tools:
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