Real-Time Systems Group
The University of Pennsylvania
VERSA: Verification Execution and Rewrite System for ACSR
To facilitate the use of the Algebra of Communicating Shared Resources
the design and analysis of real-time systems we have developed an
integrated set of tools called VERSA (Verification, Execution and
Rewrite System for ACSR). VERSA supports three types of analysis
Application of rewriting rules to ACSR specifications to deduce
Construction of a state machine and automatic exploration and
analysis of the state space to verify safety properties and test
equivalence of alternative process formulations.
Interactive execution of the process specification to explore
specific system behaviors and sample the execution traces of the
VERSA extends the basic ACSR syntax with a number of notational
conventions borrowed from programming languages. Specifications can
be broken up into logical components and recombined using file
inclusion. Symbolic constants and macros can be defined using a
#define notation similar to the C programming language.
Indexed process variable names, resource names, and event labels are
allowed. Indexed composition and set construction operators are
provided for operating on sets of indexed names.
The basic VERSA system has a command oriented interface for inputting
process descriptions, binding them to identifiers, and operating on
them. There is also a version of VERSA with an X/Motif user interface
known as X-VERSA. X-VERSA doesn't support indexed names, but it does
provide a point-and-click interface that dramatically improves the
usability of the algebraic term rewriting facility.
VERSA and X-VERSA are implemented in C++. The Lex and Yacc
compiler construction tools, the LEDA class library,
and the libg++ and X/Motif libraries were used extensively to enhance
portability. The use of a low-level programming language and the most
current algorithms state machine construction and bisimulation testing
has resulted in performance that compares very favorably with existing
process algebra analysis toolkits.
VERSA is available via ftp. Relevant files are as follows:
Sun4 compiled version of the VERSA system.
Sun4 compiled VERSA with an X/Motif wrapper. To
run, XAPPLRESDIR environment variable must point
at a directory holding XVersa.
Default resource file for X-VERSA. Must be in a
directory pointed to by the XAPPLRESDIR environment
variable to run X-VERSA.
Collection of example files for various classic
and not-so-classic concurrency problems coded in
VERSA in a Nutshell. A short VERSA tutorial
used in a course taught at Penn. Contains a few
Penn-specific references that will have to be
tailored to the local site.
VERSA: A Tool for the Specification and Analysis
of Resource-Bound Real-Time Systems.
D. Clarke, I. Lee, and H. Xie,
Journal of Computer and Software Engineering, 3(2), April 1995.
VERSA: A Tool for Analyzing Resource-Bound Real-Time Systems.
D. Clarke and I. Lee,
Special session on models and formalisms for
representing and reasoning about temporal phenomena,
IEA/AEI '94, Austin, Texas, May 1994.
VERSA: Verification, Execution and Rewrite System for ACSR.
University of Pennsylvania Technical Report MS-CIS-95-34,