Picker: Description Logic Query Engine for RDF Triples

1 Abstract

Picker is a command line query tool for RDF data, which returns complex concepts in description logics for an inputed query. You can generate more logical data from RDF data than SPARQL.

2 Download

Picker v1.0.0

3 System requirement

Java 8 or later

4 Usage

$ java -jar picker.jar --data DATA_FILE --query QUERY_FILE

5 Example

$ java -jar picker.jar --data train.ttl --query train.dq

@PREFIX     : <http://example.org/> .
@PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#> .

LANG (atom some)

SELECT ?x[3] WHERE {
        :TrainToEast rdfs:subClassOf ?x[3] .
        ?x[3] rdfs:subClassOf :TrainToEast .
}

-----------------------------------------------------------------------------------------------------------
| ?x[3]                                                                                                   |
===========================================================================================================
| (and http://example.org/TrainToEast (some http://example.org/has http://example.org/Long))              |
| (and http://example.org/TrainToEast (some http://example.org/has http://example.org/Rectangle))         |
| (and http://example.org/TrainToEast (some http://example.org/has http://example.org/Short))             |
| (some http://example.org/has (and http://example.org/Closed http://example.org/Short))                  |
| http://example.org/TrainToEast                                                                          |
| (and http://example.org/TrainToEast (some http://example.org/has http://example.org/Open))              |
| (and http://example.org/TrainToEast (some http://example.org/has http://example.org/Closed))            |

6 Query syntax

Concepts in the Description Logic SROIQ

Concept constant

Picker supports the following syntax for concepts in the description logic SROIQ.

Concept: C, D ::= TOP | BOT | <URI> | (not C) | (and C D) | (or C D) | (all R C) | (some R C) | (at-most n R C) | (at-least n R C) | (exactly n R C) (filler R i) | (self R) | (one-of i1 i2 … in)
Role: R ::= <URI> | (inverse R)
Individual: i ::= <URI>

Concept variable

Picker supports the following syntax for roles in the description logic SROIQ.

?x[n]

Here, n is the max length of concepts bound for x. The length of concepts is defined as follows:

|<URI>| = |TOP| = |BOT| = 1
|(not C)| = |C|
|(and C D)| = |(or C D)| = |C| + |D|
|(all R C)| = |(some R C>| = |R| + |C|
|R| = 1

Picker supports SPARQL-like queries such that

rdfs:subClassOf is only permitted as predicates in each triple.
Concept constants and concept variables can be used where the max length for each concept variable must be specified

Query syntax:

Query       ::= Prologue SelectQuery
Prologue    ::= PrefixDecl∗
PrefixDecl  ::= 'PREFIX' PNAME_NS '<' URI '> .'
SelectQuery ::= 'SELECT' Var+ WhereClause
WhereClause ::= 'WHERE' '{' (Triple '.')+ '}'
Triple      ::= Term ' ' rdfs:subClassOf ' ' Term
Term        ::= ConceptCon | ConceptVar

The occurence of variables in the query has the following restriction:

If your query contains a triple with two variables, e.g., ?x[n] rdfs:subClassOf ?y[m], ?x[n] and/or ?y[m] must occur the previous triple.

Example of valid query

SELECT ?x[2] ?y[3] WHERE {
   ?x[2] rdfs:subClassOf :Man .   # (1)
   ?x[2] rdfs:subClassOf ?y[3] .  # <= An concept constant is bound for ?x[2] in (1)
}

Example of invalid query

SELECT ?x[2] ?y[3] WHERE {
   ?x[2] rdfs:subClassOf ?y[3] .  # Neither ?x[2] nor ?y[3] is solved.
   ?x[2] rdfs:subClassOf :Man .
}