SPARQL queries

NeoWiki keeps SPARQL 1.1 graph stores such as QLever in sync with the wiki's structured data: each page becomes a named graph of RDF triples — one per projection the store holds — updated on each edit and dropped on deletion. This wiki's store holds the native projection. This page demonstrates the three ways to query it. It is imported only into wikis that have a SPARQL store configured, like the NeoWiki development stack.

Query with a parser function

The {{#sparql_raw}} parser function runs a read-only SPARQL query against the first configured store and returns the raw SPARQL JSON results. Entity, schema, and property IRIs are minted under the wiki's RDF base URI, which defaults to the wiki's own server URL — the examples below write it as {{SERVER}} so they work on any wiki.

Source:

{{#sparql_raw:SELECT ?museum ?visitors WHERE { ?m <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <{{SERVER}}/schema/Museum> . ?m <http://www.w3.org/2000/01/rdf-schema#label> ?museum . ?m <{{SERVER}}/prop/Annual_visitors> ?visitors } ORDER BY DESC(?visitors) LIMIT 5}}

Result:

{
    "head": {
        "vars": [
            "museum",
            "visitors"
        ]
    },
    "results": {
        "bindings": [
            {
                "museum": {
                    "type": "literal",
                    "value": "Mus\u00e9e d'Orsay"
                },
                "visitors": {
                    "datatype": "http://www.w3.org/2001/XMLSchema#int",
                    "type": "literal",
                    "value": "3270000"
                }
            },
            {
                "museum": {
                    "type": "literal",
                    "value": "Museo del Prado"
                },
                "visitors": {
                    "datatype": "http://www.w3.org/2001/XMLSchema#int",
                    "type": "literal",
                    "value": "3200000"
                }
            },
            {
                "museum": {
                    "type": "literal",
                    "value": "Rijksmuseum"
                },
                "visitors": {
                    "datatype": "http://www.w3.org/2001/XMLSchema#int",
                    "type": "literal",
                    "value": "2700000"
                }
            },
            {
                "museum": {
                    "type": "literal",
                    "value": "Kunsthistorisches Museum"
                },
                "visitors": {
                    "datatype": "http://www.w3.org/2001/XMLSchema#int",
                    "type": "literal",
                    "value": "1800000"
                }
            }
        ]
    },
    "meta": {
        "query-time-ms": 1,
        "result-size-total": 4
    }
}

Each graph is named for the projection and the page it holds — https://neowiki.dev/graph/native/page/<pageid> — so results can carry provenance, and one store can hold several projections without a page's triples in one overwriting the other's. This query lists people together with the graph each one comes from:

{{#sparql_raw:SELECT ?graph ?person WHERE { GRAPH ?graph { ?p <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <{{SERVER}}/schema/Person> . ?p <http://www.w3.org/2000/01/rdf-schema#label> ?person } } ORDER BY ?person LIMIT 5}}

Result:

{
    "head": {
        "vars": [
            "graph",
            "person"
        ]
    },
    "results": {
        "bindings": [
            {
                "graph": {
                    "type": "uri",
                    "value": "https://neowiki.dev/graph/native/page/168"
                },
                "person": {
                    "type": "literal",
                    "value": "Anna Magdalena Bach"
                }
            },
            {
                "graph": {
                    "type": "uri",
                    "value": "https://neowiki.dev/graph/native/page/164"
                },
                "person": {
                    "type": "literal",
                    "value": "Carl Philipp Emanuel Bach"
                }
            },
            {
                "graph": {
                    "type": "uri",
                    "value": "https://neowiki.dev/graph/native/page/165"
                },
                "person": {
                    "type": "literal",
                    "value": "Johann Ambrosius Bach"
                }
            },
            {
                "graph": {
                    "type": "uri",
                    "value": "https://neowiki.dev/graph/native/page/170"
                },
                "person": {
                    "type": "literal",
                    "value": "Johann Christian Bach"
                }
            },
            {
                "graph": {
                    "type": "uri",
                    "value": "https://neowiki.dev/graph/native/page/175"
                },
                "person": {
                    "type": "literal",
                    "value": "Johann Sebastian Bach"
                }
            }
        ]
    },
    "meta": {
        "query-time-ms": 1,
        "result-size-total": 5
    }
}

Query from Lua

mw.neowiki.sparqlQuery returns the same results document as a Lua table, so Scribunto modules can format it. From Module:LuaExample:

function p.largestMuseums( frame )
	local base = mw.site.server
	local result = nw.sparqlQuery(
		'SELECT ?label ?visitors WHERE { ' ..
		'?m <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <' .. base .. '/schema/Museum> . ' ..
		'?m <http://www.w3.org/2000/01/rdf-schema#label> ?label . ' ..
		'?m <' .. base .. '/prop/Annual_visitors> ?visitors ' ..
		'} ORDER BY DESC(?visitors) LIMIT 3'
	)

	local list = {}
	for _, binding in ipairs( result.results.bindings ) do
		list[#list + 1] = '* ' .. binding.label.value .. ' (' .. binding.visitors.value .. ' visitors)'
	end
	return table.concat( list, '\n' )
end

Invoke it from wikitext:

{{#invoke:LuaExample|largestMuseums}}

Result:

• Musée d'Orsay (3270000 visitors)
• Museo del Prado (3200000 visitors)
• Rijksmuseum (2700000 visitors)

Query over REST

The same queries work over the wiki's REST API, which returns the results document as JSON:

POST https://neowiki.dev/w/rest.php/neowiki/v0/query/sparql

{ "query": "SELECT ?label WHERE { ?s <http://www.w3.org/2000/01/rdf-schema#label> ?label } LIMIT 5" }

For details, see the query API, parser function, and Lua documentation. For querying the property graph with Cypher instead, see Developers.