PAC is a predicate-argument clustering software which is trained on tuples such as

2    abandon    SUBJ:NP    company    project  

and induces a statistical soft clustering of these (and other) tuples. The statistical PAC model is described in the following paper:

Sabine Schulte im Walde, Christian Hying, Christian Scheible, and Helmut Schmid:
Combining EM Training and the MDL Principle for an Automatic Verb Classification Incorporating Selectional Preferences,
ACL-HLT 2008, Columbus, Ohio. (pdf)

The source code of PAC can be downloaded here as a gzip-compressed tar file. It is freely available for education, research and other non-commercial purposes.

Please send comments, suggestions and bug reports to me (Helmut Schmid) at the address