Dr David Flater, Dr Philippe Martin and Michelle L. Crane (2009).
Rendering UML Activity Diagrams as Human-Readable Text.
To be published in the proceedings of IKE 2009, international conference on Information and Knowledge Engineering, July 13-16, 2009, Nevada, USA.

This article was also published as "NISTIR report 7469" (National Institute of Standards and Technology, Gaithersburg, MD) in 2007
HTML version:  on the NIST site,  on this site.
PDF version:  on the NIST site,  on this site.