Carlos referred to "Petri Nets" in his e-mail. For those not familiar with Petri Nets (I was not), I found a Web site that gives an overview of Coloured Petri Nets (CPN), an extension: http://www.daimi.au.dk/CPnets/intro/ Petri Nets date back to the 60's. They aren't directly applicable (I far as I can tell) to our bioinformatics-specific communication model. But they share many similarities, particularly with the Glyphic Command Language we will use on the benchtop to represent connected loci, documents, analyses, etc. Jeff -- J.W. Bizzaro Phone: 617-552-3905 Boston College mailto:bizzaro at bc.edu Department of Chemistry http://www.uml.edu/Dept/Chem/Bizzaro/ --