README.asciidoc

SPARQL-Gremlin

SPARQL-Gremlin is a compiler used to transform SPARQL queries into Gremlin traversals. It is based on the Apache Jena SPARQL processor ARQ, which provides access to a syntax tree of a SPARQL query.

The current version of SPARQL-Gremlin only uses a subset of the features provided by Apache Jena. The examples below show each implemented feature.

Quick Start

Console Application

The project contains a console application that can be used to compile SPARQL queries and evaluate the resulting Gremlin traversals. For usage examples simply run ${PROJECT_HOME}/bin/sparql-gremlin.sh.

Gremlin Shell Plugin

To use Gremlin-SPARQL as a Gremlin shell plugin, run the following commands (be sure sparql-gremlin-xyz.jar is in the classpath):

gremlin> :install com.datastax sparql-gremlin 0.1
==>Loaded: [com.datastax, sparql-gremlin, 0.1]
gremlin> :plugin use datastax.sparql
==>datastax.sparql activated

Once the plugin is installed and activated, establish a remote connection to execute SPARQL queries:

gremlin> :remote connect datastax.sparql graph
==>SPARQL[graphtraversalsource[tinkergraph[vertices:6 edges:6], standard]]
gremlin> :> SELECT ?name ?age WHERE { ?person v:name ?name . ?person v:age ?age }
==>[name:marko, age:29]
==>[name:vadas, age:27]
==>[name:josh, age:32]
==>[name:peter, age:35]

Prefixes

SPARQL-Gremlin supports the following prefixes to traverse the graph:

Prefix	Purpose
e:<label>	out-edge traversal
p:<name>	property traversal
v:<name>	property-value traversal

Note that element IDs and labels are treated like normal properties, hence they can be accessed using the same pattern:

SELECT ?name ?id ?label WHERE { ?element v:name ?name . ?element v:id ?id . ?element v:label ?label }

Examples

Select All

Select all vertices in the graph.

SELECT * WHERE {
}

Match Constant Values

Select all vertices with the label person.

SELECT * WHERE {
  ?person v:label "person"
}

Select Specific Elements

Select the values of the properties name and age for each person vertex.

SELECT ?name ?age
WHERE {
  ?person v:label "person" .
  ?person v:name ?name .
  ?person v:age ?age
}

Pattern Matching

Select only those persons who created a project.

SELECT ?name ?age
WHERE {
  ?person v:label "person" .
  ?person v:name ?name .
  ?person v:age ?age .
  ?person e:created ?project
}

Filtering

Select only those persons who are older than 30.

SELECT ?name ?age
WHERE {
  ?person v:label "person" .
  ?person v:name ?name .
  ?person v:age ?age .
  ?person e:created ?project .
    FILTER (?age > 30)
}

Deduplication

Select the distinct names of the created projects.

SELECT DISTINCT ?name
WHERE {
  ?person v:label "person" .
  ?person e:created ?project .
  ?project v:name ?name .
    FILTER (?age > 30)
}

Multiple Filters

Select the distinct names of all Java projects.

SELECT DISTINCT ?name
WHERE {
  ?person v:label "person" .
  ?person e:created ?project .
  ?project v:name ?name .
  ?project v:lang ?lang .
    FILTER (?age > 30 && ?lang == "java")
}

Pattern Filter

A different way to filter all person who created a project.

SELECT ?name
WHERE {
  ?person v:label "person" .
  ?person v:name ?name .
    FILTER EXISTS { ?person e:created ?project }
}

Filter all person who did not create a project.

SELECT ?name
WHERE {
  ?person v:label "person" .
  ?person v:name ?name .
    FILTER NOT EXISTS { ?person e:created ?project }
}

Meta-Property Access

SELECT ?name ?startTime
WHERE {
  ?person v:name "daniel" .
  ?person p:location ?location .
  ?location v:value ?name .
  ?location v:startTime ?startTime
}