README

RDFSim
======

This Python library helps generating a vector space from very large hierarchies encoded in RDF. An obvious example application is to generate a vector space from a SKOS hierarchy or an RDFS subclass hierarchy.

Getting started
---------------

Running the tests:

    $ nosetests

Installing:
 
    $ python setup.py install

Example use
-----------

    $ wget http://downloads.dbpedia.org/3.7/en/skos_categories_en.nt.bz2
    $ bunzip2 skos_categories_en.nt.bz2
    $ python
    >>> from rdfsim.space import Space
    >>> space = Space('skos_categories_en.nt')
    >>> space.similarity_uri(category1, category2)

Constructing a vector space for the entire DBpedia SKOS category
hierarchy (3M triples) takes a couple of minutes on a commodity laptop, 
and has a memory footprint of about 500M.

Alternatively, a subset of it is available in the examples/ directory.

How it works
------------

For each topic t in the hierarchy, we consider the set of its parents
parents(t, k) at a level k. We construct a vector for each t in a space
where each dimension corresponds to a topic d in the hierarchy. The value
of t on dimension d is defined as follows:

    t_d = \sum_{k = 0}^{max_depth} \sum_{d \in parents(t, k)} decay^k

where max_depth and decay are two parameters, which can be used to influence
how much importance we attach to ancestors that are high in the
category hierarchy.

They can be specified as follows:

    >>> Space.max_depth = 8
    >>> Space.decay = 0.9

Licensing terms and authorship
------------------------------

See 'COPYING' and 'AUTHORS' files.