Extended Transition Network

by Stephen Cook

The Extended Transition Network (ETN) is a flavour of labelled transition system which is particularly suitable for modelling information systems. The usual modelling approaches (eg SSADM) differentiate strongly process and data modelling. ETN technology provides the possibility to combine these two aspects elegantly with constraints and triggers to provide a complete and unified modelling environment from conceptual level down to detailed systems design specifications. The concept was devised initially by Keith Jeffery (CLRC) and developed further jointly with Patrizia Asirelli (IEI-CNR), under the auspices of the ERCIM Database Research Group.

Recently this collaboration between CLRC and IEI has been strengthened by an ERCIM Internal Fellowship. This enabled Stephen Cook, from CLRC's Data Engineering Group, to spend three months at IEI working on ETN and gaining first-hand experience of the GEDBLOG logic database which provides the deductive engine for the ETN environment.

As a result, the ETN project has made significant progress in three areas:

• the ETN formalism now has a more complete and formal semantics. This should provide a sound basis for future work, for example, extending ETN to enterprise modelling and to concurrent and time-dependent systems
• the semantics of ETN have been implemented as construction rules expressed as a GEDBLOG theory. This provides a valuable demonstration of GEDBLOG's suitability for reasoning about system development
• the Fellowship provided an opportunity to examine how the ETN project should move forward. A project proposal is being developed jointly by CLRC and IEI which links ETN to other software engineering tools to provide a comprehensive environment for system verification.

Interim results from the Fellowship are available in Postscript form from ftp://rep1.iei.pi.cnr.it/pub/asirelli/ETNrules.ps and will be published as an IEI Technical Report.