Exploring Graphs with Elixir/

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Case 2: Graph Walk (Querying)

Case 2: Graph Walk (Querying)

Explore DBpedia and get introduced to linked open data.

We'll cover the following...

Let’s take a short walk through DBpedia. We’ll do this in two different ways—first by querying DBpedia and second by browsing DBpedia. Let’s start with querying.

Module creation

The first thing we do is create a new module. We create a new folder named examples/ under our rdf_graph/lib/rdf_graph/ folder. Under that, we create a walk_query.ex file:

Next, we create a new module and add in a walk_query/2 function as follows:

#
# RDF4J configuration template for a GraphDB repository
#
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>.
@prefix rep: <http://www.openrdf.org/config/repository#>.
@prefix sr: <http://www.openrdf.org/config/repository/sail#>.
@prefix sail: <http://www.openrdf.org/config/sail#>.
@prefix graphdb: <http://www.ontotext.com/config/graphdb#>.

[] a rep:Repository ;
rep:repositoryID "ex-graphs-book" ;
rdfs:label "" ;
rep:repositoryImpl [
    rep:repositoryType "graphdb:SailRepository" ;
    sr:sailImpl [
        sail:sailType "graphdb:Sail" ;

        graphdb:base-URL "http://example.org/owlim#" ;
        graphdb:defaultNS "" ;
        graphdb:entity-index-size "10000000" ;
        graphdb:entity-id-size  "32" ;
        graphdb:imports "" ;
            graphdb:repository-type "file-repository" ;
        graphdb:ruleset "rdfsplus-optimized" ;
        graphdb:storage-folder "storage" ;

        graphdb:enable-context-index "false" ;

        graphdb:enablePredicateList "true" ;

        graphdb:in-memory-literal-properties "true" ;
        graphdb:enable-literal-index "true" ;

        graphdb:check-for-inconsistencies "false" ;
        graphdb:disable-sameAs  "true" ;
        graphdb:query-timeout  "0" ;
        graphdb:query-limit-results  "0" ;
        graphdb:throw-QueryEvaluationException-on-timeout "false" ;
        graphdb:read-only "false" ;
    ]
].
WalkQuery module

Line 4: We define our walk_query/2 function with two optional parameters: a link for our graph start ...