A computed property (also known as property functions or magic properties) is a predicate that occurs in a SPARQL query pattern with matching semantics other than simple subgraph matching. One common example use case for this is providing a predicate that relates an RDF list subject to the member items of the list. Another common example is providing a computed property that relates string literal subjects to free-text (a la Lucene) search strings.
- ARQ supports property functions and has a library of such functions in addition to allowing developers to register their own. For example, ARQ's free text search using Lucene.
- Glitter has a similar mechanism called functional predicates and uses it for searching Lucene text indexes.
- AllegroGraph uses a magic predicate for free text searching. AllegroGraph also provides generalized support for computed properties to enable Geospatial, Temporal and Social Network Analysis in SPARQL.
- Virtuoso uses a magic predicate for free text searching. ?? Does Virtuoso provide generalized support for computed properties?