Formal Specification of PLAN

We would like to announce the availability of a draft specification for
the Packet Language for Active Networks at
We welcome feedback on the draft specification and hope to resolve a
first non-draft version in the fall.

PLAN is a packet-based scripting language designed by the SwitchWare
group at the University of Pennsylvania for configuring, composing, and
invoking router-resident services for active networking.  Although it is
not an essential feature of the language, PLAN implementations
have generally been carried out for service layers programmed in
specific languages.  We are aware of efforts for OCaml, Java, C, C++,
and typed assembly.  Version 3.1 of the SwitchWare OCaml implementation
has been tested to conform to the specification.  Information and
software for PLAN can be found at the PLAN home page

The specification has several purposes.  First, it is meant to serve as
a means to communicate PLAN design ideas between implementors.  Second,
a PLAN standard should assist portability of PLAN programs between
implementations.  Third, it will make it easier to create tutorials for
PLAN that are meaningful for more than one implementation.  Finally, the
PLAN specification is given formally and could be used as the basis of
automated mathematical analysis of the language, its implementations,
and programs written in the PLAN.

Comments about the PLAN specification can be directed to the PLAN
Discussion List, PLAN-disc@dsl.cis.upenn.edu, or, if you prefer, to
gunter@cis.upenn.edu and pankaj@dsl.cis.upenn.edu.

                                       Carl A. Gunter and Pankaj Kakkar