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README-SBS.md

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SPARQL Binding Streams (SBS)

The sbs tool allows one to pass a SPARQL result sets to a given query. The incoming result set replaces the given query's query pattern - hence it is ignored and can be left empty such as in sbs map -s 'SELECT * {}' input.rsj. The main use case is to post process result sets that are assembled from multiple individual queries such as the output of the Named Graph Streams (NGS) tool which is part of the bundle.

The typical conventions of the RDF Processing Toolkit apply:

  • The SELECT keyword is optional - so ?s { ?s a foaf:Person} is equivalent to SELECT ?s WHERE { ?s a foaf:Person }
  • IRIs starting with <env:> will be substituted with environment variable values. There by <env:USER> yields a string and using double slashes such as <env://JAVA_HOME> a IRI> yields IRIs.

Example:

sparql-integrate -o txt '(<env:USER> AS ?user) {}'

-----------
| user    |
===========
| "raven" |
-----------
➜  sbs -h
Usage: sbs [-h] [COMMAND]
SPARQL Binding Streams Subcommands
  -h, --help
Commands:
  map     Map bindings via queries
  filter  Filter bindings by an expression
Usage: sbs map [-h] [-o=<outFormat>] [-s=<queries>]... [<nonOptionArgs>...]
Map bindings via queries
      [<nonOptionArgs>...]   Input files
  -h, --help
  -o, --out-format=<outFormat>

  -s, --sparql=<queries>     SPARQL statements; only queries allowed

Supported Input Format

SBS builds upon Apache Jena's ResultSetMgr and thus supports all its formats.

Building

SBS is part of the rdf-processing-toolkit build. Installing the debian package also makes the command sbs tool available.

Example Usage

  • Save a result set to a file (by default in json) and later see for each type how many subjects there are:
    • sparql-integrate data.ttl '* { ?s a ?t } > types.srj
    • sbs -o txt -s '?t (COUNT(DISTINCT ?s)) {} GROUP BY ?t ORDER BY DESC (COUNT(DISTINCT ?s))' types.srj
    • cat types.srj | sbs -o txt -s '?t (COUNT(DISTINCT ?s)) {} GROUP BY ?t ORDER BY DESC (COUNT(DISTINCT ?s)) works as well