Linear recursive querying over a graph database

A non-transitory computer-readable storage medium having recorded thereon a computer program having instructions for performing a method for executing, by a query engine, a linear recursive query on an RDF graph database, the method comprising:

• obtaining a first part of the query that defines as input one or more initial conditions of at least one of query elements in a second part of the query on the RDF graph database;
• and
• obtaining at least two clauses, the at least two clauses together specifying that the second part of the query will be executed recursively:
• a first clause defining how an output of an execution of the second part of the query is used as an input of a next execution of the second part of the query, and
• a second clause defining the second part of the query, the second clause comprising the query elements describing how the output of an execution of the second part is queried using (i) the input of the one or more initial conditions for an initial execution of the second part of the query or (ii) the output of a previous execution of the second part of the query for the next execution of the second part of the query.

A computer system comprising:

• a processor coupled to a memory, the memory having recorded thereon a computer program having instructions for executing, by a query engine, a linear recursive query on an RDF graph database, that when executed by the processor causes the processor to be configured to:
• obtain a first part of the query that defines as input one or more initial conditions of at least one of query elements in a second part of the query on the RDF graph database;
• and
• obtain at least two clauses, the at least two clauses together specifying that the second part of the query will be executed recursively:
• a first clause defining how an output of an execution of the second part of the query is used as an input of a next execution of the second part of the query, and
• a second clause defining the second part of the query, the second clause including the query elements describing how the output of an execution of the second part is queried using (i) the input of the one or more initial conditions for an initial execution of the second part of the query or (ii) the output of a previous execution of the second part of the query for the next execution of the second part of the query.