Joseki supports the dynamic loading of query language processors when the server starts. These query modules can be provided externally by the application or by some other party. The functionally provided with the Joseki distribution is just such modules dynamically loaded according to teh standard Joseki definitions file.
This page gives the HTTP binding of the query languages. All queries return a matching subgraph by default. See also: the Joseki RDF WebAPI description.
The Joseki distribution supports HTTP GET and provides the following query languages:
There are classes in the Java and Python client-libraries to make queries in these various query languages without needing to understand the HTTP encoding of them.
A plain HTTP GET (no query string) is handled internally as a query request for the whole model.
URI: http://jena.hpl.hp.com/2003/07/query/RDQL
See also: The Jena RDQL Tutorial
| Parameter Name | Parameter Type/Value | Description |
|---|---|---|
| lang (required) |
Id. of query language |
URI: http://jena.hpl.hp.com/2003/07/query/RDQL |
| query (required) |
The query, as %encoded string |
The RDQL query to be executed. As with all parameter values, this must be %-encoded. |
| format (optional) |
"BV" |
Other RDF graphs for the output formats for the
result graph. |
| closure (optional) |
"true" or "false" |
For each binding of a variable mentioned in the SELECT clause, which is bound to a bNode, the graph is augmented with the bNode closure from this point. |
The bNode closure from a bNode is formed by adding all the statement with that node as subject, then recursing over any additional bNodes added as objects of those statements. Recursion stops where literals or labelled nodes are encountered. Cycles are detected and handled by avoiding infinite loops.
Only one format" parameter may be given. "BV" is alternatively http://jena.hpl.hp.com/2003/07/query/BV
URI: http://jena.hpl.hp.com/2003/07/query/fetch
The fetch query language implements the idea of RDF data objects. A query consists of single "r" parameter, whose value is the URIref of the data object. Alternatively, a "p" parameter and an object value ("o" for URIref, "v" for string literal) can be used to identify the resource: if there is more than one, fetches on all the resource s are merged.
The exact extent of the RDF returned is dependent on the server. Joseki provides a module that provides all statements with the resource as subject, then calculates the bNode closure of all objects of these statements. This is used in the book database examples.
| Parameter Name | Parameter Value | Description |
|---|---|---|
| lang (required) |
Id. of query language |
URI: http://jena.hpl.hp.com/2003/07/query/fetch |
| r (either 'p' or 'r') |
URIref | URIref of the resource |
| p (either 'p' or 'r') |
URIref | URIref of the property |
| o (either 'o' or 'v' with 'p') |
URIref | URIref of the object of the triple pattern. Only one of "o" and "v" may be given |
| v (either 'o' or 'v' with 'p') |
String | Literal value as a string. Absence or "o" and"v" implies a wildcard match. |
There are two forms of a fetch request:
URI: http://jena.hpl.hp.com/2003/07/query/SPO
SPO (also known as "Triples") is an experimental minimal query language. An SPO query is a single triple pattern, with optional subject (parameter "s"), predicate (parameter "p"), and object (parameter "o", if a URIref, parameter "v" for a string literal). Absence of a parameter implies "any" for matching that slot of the triple pattern.
Such a query language is not suitable for all situations but is convenient some record oriented vocabularies, for example, simple Dublin Core.
| Parameter Name | Parameter Value | Description |
|---|---|---|
| lang (required) |
Id. of query language |
URI: http://jena.hpl.hp.com/2003/07/query/SPO |
| s (optional) |
URIref |
URIref of the subject of the triple pattern. Absence implies a wildcard match. |
| p (optional) |
URIref | URIref of the subject of the triple pattern. Absence implies a wildcard match. |
| o (optional) |
URIref | URIref of the object of the triple pattern. Only one of "o" and "v" may be given |
| v (optional) |
String | Literal value as a string. Absence or "o" and"v" implies a wildcard match. |
| closure (optional) |
"true" or "false" | Calculate the bNode closure of the matched subgraph. |