Store SPARQL Service

URI Pattern

Each item in the store has its own URI based on its unique identifier:

http://api.talis.com/stores/{storename}/services/sparql

Resource Operations

URI Pattern	Method	Request Body	Semantics	Capability required
`/services/sparql`	GET		Retrieve a simple query form	None
`/services/sparql?query=`	GET		Perform a SPARQL search	None
	POST	`application/x-www-form-urlencoded` parameters	Perform a SPARQL search	None

Request Parameters

Parameter	Required?	Description	Values
`query`	Yes	The SPARQL query to perform	A SPARQL query
`output`	No	Specify the output format	See below
callback	No	Specify the callback function for a JSONP request	A JSONP callback function

Additional Options & Restrictions

Specifying the Data Set

The SPARQL service associated with a platform store uses a fixed default (background) graph. The contents of this graph is the contents of the Metabox.

The service does not support specifying the dataset in either the protocol (using default-graph-uri and named-graph-uri parameters) or within the SPARQL query itself (using FROM and FROM NAMED).

The Store Multisparql Service does provide some additional options for querying multiple graphs.

Output Formats

The following table summarizes the different output formats supported by the SPARQL service. The output types can be selected using Content Negotiation using either the Accept header or the output parameter. The Sparql Service also supports javascript (jsonp) output (see the JSONP Javascript Output section below).

SPARQL Query Type	Output Param Value	Mime Type	Schema
SELECT	`xml`	`application/sparql-results+xml`	SPARQL Query Results XML Format
	`json`	`application/sparql-results+json`	Serializing SPARQL Query Results in JSON Format
ASK	`xml`	`application/sparql-results+xml`	SPARQL Query Results XML Format
	`json`	`application/sparql-results+json`	Serializing SPARQL Query Results in JSON Format
CONSTRUCT	`xml` or `rdf`	`application/rdf+xml`	RDF/XML Syntax
	`json`	`application/json`	RDF/JSON Syntax
	`ntriples`	`text/plain`	N-Triples
	`turtle`	`text/turtle`	Turtle
DESCRIBE	`xml` or `rdf`	`application/rdf+xml`	RDF/XML Syntax
	`json`	`application/json`	RDF/JSON Syntax
	`ntriples`	`text/plain`	N-Triples
	`turtle`	`text/turtle`	Turtle

Note: for backwards compatibility, where the text/turtle media type is listed, the deprecated application/x-turtle media type is also supported, though it is given a lower weighting during Content Negotiation

JSONP (Javascript) Output

The following table summarizes the content-negotiation logic for obtaining the sparql results as JSONP using the output (or Accept header) and the callback parameter (see here for all the logic). The output parameter, if set, will override the Accept header.

Output Param Value	Accept Header	Callback	Output Format
json	application/javascript	{valid javascript identifier}	JSONP with mime-type application/javascript
{NOT json, e.g., xml}	application/javascript	{valid javascript identifier}	XML format depending on the query type - see Output Formats section above. (Because output overrides the Accept header and callback)
json	/	{valid javascript identifier}	JSONP with mime-type application/javascript
	/	{valid javascript identifier}	JSONP with mime-type application/javascript
		{valid javascript identifier	JSONP with mime-type application/javascript ("If no Accept header field is present, then it is assumed that the client accept all media types")
json		{valid javascript identifier}	JSONP with mime-type application/javascript
	application/javascript	{valid javascript identifier}	JSONP with mime-type application/javascript
json			JSON format (see table in Output Formats section above). This is the case if callback is either empty or doesn't exist.
	Is set e.g., application/xml (NOT application/javascript OR / OR no header)	{valid javascript identifier}	XML format depending on the query type - see Output Formats section above. (Because no output parameter is set and the Accept header does not include javascript.)

It is the combination of the output parameter (or Accept header) and the callback parameter that specifies JSONP output. If the output parameter is any other value than json, (or the Accept header is not application/javascript or */*) then the callback parameter will be ignored.

Only valid javascript identifiers are allowed as the callback parameter value.

Restrictions on Query Times

The SPARQL service endpoint enforces a maximum execution time for all SPARQL queries. This is to ensure that long-running queries do not degrade the service for other users. Queries that exceed the maximum allowable time will be terminated and a 500 Internal Server error response returned.

SPARQL Extensions

The SPARQL service endpoint includes support for some extensions to the SPARQL query language. The full list of SPARQL Extensions are documented separately.

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