The Changeset Protocol for RDF describes the behaviour of a service capable of processing RDF descriptions of Changesets and processing their application to an underlying RDF store. The protocol specifies two operations versioned_update and unversioned_update.

A service implementing the protocol may expose either or both of the update operations, and so may function in two modes:

• versioned_update - the changes detailed by the Changeset should be applied to the underlying RDF Store and the Changeset description itself stored in the same RDF store
• unversioned_update - the changes detailed by the Changeset should be applied to the underlying RDF Store, the Changeset description itself should then be discarded

Common Behaviour

The following is the expected behaviour of both types of changeset service.

• The removals and additions described by the changeset are applied to the underlying model - no checking is done to ensure that the rdf:subject of the reified statements match the Changeset's cs:subjectOfChange
• The response code from POSTing a RDF/XML document containing two changesets with the same subject of change is 400
• The response code from POSTing a RDF/XML document containing two changesets with different subjects of change is 400
• A POSTed changeset will only be applied if all the removal statements exist in the model. Failure will be indicated with HTTP status code 409

Versioned Update

The following is the expected behaviour of a Changeset versioned changeset service. Names in brackets after each behaviour is the name of the corresponding acceptance test in the test suite.

• Look for any preceding changesets with the same cs:subjectOfChange, if found the URI of the most recent will be set as the value of the cs:precedingChangeset property for the new changeset.
• The information about the changeset itself is added to the underlying model - this includes the reified forms of the changesets's additions/removals.
• A triple of the form <subjectOfChange> dir:etag "xyz" . should be created as a consequence of a successful request. The value of the etag should be unique.
• The response body from POSTing a valid changeset contains the stored changeset
• The response headers from POSTing a valid changeset includes a Location header containing the URI of the stored changeset
• The response code from POSTing a valid changeset is 201
• The response code from POSTing a changeset without a change reason is 400
• The response code from POSTing a changeset without a creator is 400
• The changeset returned in the response body includes a created date property if none was specified in the POSTed data
• The changeset returned in the response body replaces the created date property if it was specified in the POSTed data
• POSTing a changeset with a blank node as the cs:subjectOfChange replaces that blank node with a generated URI. The changes in the changeset are applied to this URI
• The response code from POSTing a RDF/XML document containing two changesets with the same cs:subjectOfChange is 400
• The response code from POSTing a RDF/XML document containing two changesets with different cs:subjectsOfChange is 400

Unversioned Update

The following is the expected behaviour of the unversioned changeset service.

• The response code from POSTing a valid changeset is 204
• The response body from POSTing a valid changeset is empty
• POSTing a changeset with a blank node as the cs:subjectOfChange replaces that blank node with a generated URI. The changes in the changeset are applied to this URI.

Summary of HTTP Behaviour

Examples

Using cURL

Unsecured changeset:

curl -H "content-type:application/vnd.talis.changeset+xml" --data @file.rdf http://api.talis.com/stores/mystore/meta

Secured:

curl --digest -u "user:password"  -H "content-type:application/vnd.talis.changeset+xml" --data @file.rdf http://api.talis.com/stores/mystore/meta

Using PHP

    $poster = curl_init("http://api.talis.com/stores/mystore/meta");

    $headers = array();
    $headers['Content-type'] = 'application/vnd.talis.changeset+xml';

    curl_setopt($poster, CURLOPT_RETURNTRANSFER,1); 
    curl_setopt($poster, CURLOPT_FOLLOWLOCATION, TRUE);
    curl_setopt($poster, CURLOPT_CONNECTTIMEOUT, 2);
    curl_setopt($poster, CURLOPT_TIMEOUT, 4);
    curl_setopt($poster, CURLOPT_HTTPHEADER, headers  );
    curl_setopt($poster, CURLOPT_HEADER, 1);

    curl_setopt($poster, CURLOPT_CUSTOMREQUEST, 'POST' ); 
    curl_setopt($poster, CURLOPT_POSTFIELDS, $changeset );

    $response = curl_exec($poster);