Fedora Resource Index Search Service

Language

Indicates the query language to use. Valid options are iTQL (a full-featured RDF query language supported by the Kowari Metastore), and RDQL, (a less powerful, but more widely supported query language popularized by the Jena Framework).

Response

Indicates the desired response format. Valid options include:

• CSV - Comma-separated values
• Simple - A simple easy-to-read text format that shows datatype information, when present.
• Sparql - An XML format for query responses designed by the RDF Data Access Working Group
• TSV - Tab-separated values

Limit

The maximum number of results to return. It is useful to set this low when testing queries.

Advanced

• Force Distinct - Whether to force duplicate results to be dropped. This is only useful for certain RDQL queries (iTQL never returns duplicates).
• Fake Media-Types - Whether to send incorrect Content-Type HTTP response headers with the responses (to trick browsers into displaying the results instead of popping up a "Save As/Open With" window).
• Stream Immediately - Whether to stream the results right away (faster), or to save them to a temporary file before sending them to the client. The default behavior (to save the results before streaming) will give a more informative error message if a query fails.

SPO

This is a very simple RDF query language, where queries consist of a specific subject (or an asterisk, indicating "any"), a specific predicate (or an asterisk), and a specific object (or an asterisk). The easiest way to learn SPO is by example:

Get all triples in the repository

    * * *

Get all triples where the object is demo:1

    * * <info:fedora/demo:1>

Get all triples where the subject is demo:1 and the object is demo:2

    <info:fedora/demo:1> * <info:fedora/demo:2>

Response Formats

A variety of RDF formats are supported:

• N-Triples - A subset of Notation 3 defined in the RDF Test Cases document.
• Notation 3 - The original RDF text format, defined by Tim Berners-Lee in An RDF language for the Semantic Web.
• RDF/XML - The "RDF/XML" format, defined in the RDF/XML Syntax Specification.
• Turtle - A newer subset of Notation 3, defined in Dave Beckett's Turtle - Terse RDF Triple Language.

Using Templates

Templates are used to convert tuple query results to triples. A template consists of one ore more triple binding patterns that reference the binding variables in an iTQL or RDQL query.

The easiest way to understand how this works is by example.

In this example, we'll show how to extract a subgraph from the resource index using iTQL. Enter the following query text:

select $a $r $b from <#ri>
where  $a <rdf:type> <fedora-model:FedoraObject>
and    $a $r $b
and    $b <rdf:type> <fedora-model:FedoraObject>

This query by itself returns all relationships between data objects in a repository. The binding variables are $a, $r, and $b. Now enter the following in the template text box:

$a $r $b

When you launch the query, you'll see a list of triples: the sub-graph of all object-to-object relationships in the repository. (If you don't see anything, you should ingest the demo objects which include some sample relationships).

Now try the following template instead. This demonstrates how to derive new statements from those in the resource index:

$a <urn:example:isRelatedTo> $b
$b <urn:example:isRelatedTo> $a

Running the query will now show two statements for every object-to-object relationship in the resource index graph.

Note: When using templates to transform tuples to triples, some duplicates may be returned. These can be avoided by checking "Force Distinct".

C. Show Aliases

This tab shows the aliases that can be used in queries and what URI prefixes they map to.

Aliases are just shortcuts that help make queries easier to write. For example, in a query you can write <fedora-model:state> instead of <info:fedora/fedora-system:def/model#state>.