Dataquay

0.3

About Dataquay

Dataquay is a free open source library that provides a friendly C++ API for the popular Redland RDF data store using Qt4 classes and containers.

Dataquay is intended to be simple to use and easy to integrate. It is principally intended for use in Qt-based applications that would like to use an RDF datastore as backing for in-memory project data, to avoid having to provide application data-specific file formats and to make it easy to augment the data with descriptive metadata pulled in from external sources. Dataquay is also intended to be useful for applications whose primary purpose is not related to RDF but that have ad-hoc RDF needs for metadata management.

What's in Dataquay?

Dataquay contains C++ abstractions for the RDF Node and Triple (or statement), and for the RDF Store. The standard BasicStore offers simple add, remove, matching, and querying functions and file I/O.

Also provided is TransactionalStore, a transactional interface to the store that offers per-thread isolation, atomic commit, and a Connection class in the style of a traditional relational database interface.

Dataquay also offers ObjectMapper, a facility which can take care of a complete object hierarchy, map it to the RDF store, and synchronise in both directions any changes to the hierarchy or the store. Arbitrary mappings between C++ class and property names and RDF URIs can be specified using TypeMapping. The mapping is flexible enough to allow you to load many publicly generated Linked Data sources directly into object class hierarchies, if you wish (although this is not usually an ideal way to handle unpredictable data sources). The classes that manage the object-to-store and store-to-object mapping can also be used separately, as ObjectStorer and ObjectLoader.

Start Here...

If you want your application to have access to RDF metadata but you are not intending to make RDF data the core of the application, then you probably want to focus on BasicStore. This can load and save RDF and perform queries, matches, and updates in a simple form.

If you need to carry out updates to RDF data, particularly in a multi-threaded application, then you should look at TransactionalStore and its related Connection class.

If you would like to use an RDF store as a "hibernation" mechanism for store and recall of an object hierarchy in an open and portable manner, then you could consider using a BasicStore, wrapping that in a TransactionalStore, and using ObjectMapper to deal with the hibernation side of things.

In any of these cases you'll also want to look closely at the Uri, Node, and Triple classes.

Development Status

Certain aspects of Dataquay are still somewhat provisional, and the API may continue to change until the 1.0 release. However, most of the API design is likely to remain as it is now and the library has been reasonably well tested. The main focus for 1.0 is to expand the test suite and produce some more example code. Those activities might show up other things that need doing too, though.

Licence

Dataquay is published under a liberal BSD-style licence, similar to (and of course compatible with) the Apache licence used by Redland. You can use it without fee in open-source or proprietary applications. See the COPYING file for details.