Locating provenance for a RESTful web service

This blog post shows how RESTful web services can provide, and link to, provenance data for their exposed resources by using the PROV-AQ mechanism of HTTP Link headers. This is demonstrated by showing how to update a hello world REST service implemented with Java and JAX-RS 2.0 to provide these links.

The  PROV-AQ HTTP mechanism is easiest explained by an example:

GET http://example.com/resource.html HTTP/1.1
Accept: text/html
HTTP/1.1 200 OK
Content-type: text/html
Link: <http://example.com/resource-provenance&gt;;
rel="http://www.w3.org/ns/prov#has_provenance&quot;;
anchor="http://example.com/resource&quot;
<html>
<!– … –>
</html>

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This request for http://example.com/resource.html returns some HTML, but also provides a Link: header that says that the provenance is located at http://example.com/resource-provenance. Within this file, the resource is known as the anchor http://example.com/resource rather than http://example.com/resource.html. The anchor URI can be omitted if it is the same as the one requested.

Link headers are specified by RFC 5988, which also defines standard relations like rel="previous". PROV-AQ uses rel="http://www.w3.org/ns/prov#has_provenance" to say that the linked resource has the provenance data for the requested resource. PROV-AQ also defines other relations for provenance query services and provenance pingback, which is not covered by this blog post.

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