Date[ 11:31:04     ]  Recordnr[        ]  Stored[ Papers Composition
Who[ J.R.Callahan, J.M Purtilo, University of Maryland
Title[ A Packaging System for Heterogeneous Execution Environments

Published[ IEEE Transactions on Software Engineering, vol.17, 1991, 
pp.626-635

Keywords[ MIL, Polygen, Polylith

Comment[ more for small, on-one-site components, strenth is partitioning 
and automatic reasoning about possible configurations, yet automatic 
generation is limitied to certain environments

Summary[ 

Polylith: TCP/IP-based communication systems for various languages.
Polygen: Composotion and reasoning tool.

What it is about:
- generation of custom interface software for heterogeneous 
configurations.
- in contrast to other approaches, not only stub generation, but 
inserting configuration methods needed to integrate an application (e.g. 
main, wrappers/dispachter program for LISP-procedures, byteswap 
functions for adjusting integers to various representations, rendezvous 
functions)
- polygen changes source code and adds necessary lines and stubs so they 
can work over network
- all is automatic, user just has to specify desired geometry
- logical design is separated from the geometry 

Composition process:
Starting point: several source files (C, Ada, Pascal, Lisp) that contain 
modules(procedure calls) to be composed.

In the extraction phase, module specs are gained from the source files, 
or these module specs already exist. Module specs: are written in 
Polylith MIL (module interconnection language). It contains the 
interfaces a module offers and uses and the parameters of these 
procedure calls.

In the composition phase, the user adds the design and annotated design 
(with geometric data) to the specs. The design says which modules are to 
be used, which communication system, where the modules are.

Then in the generatin phase POLYGEN makes a package based on the 
configuration rules it has. Configuration rules are added by the Polygen 
system maintainer and say what kind of modules can be connected how. 
A package (valid configuration represented in an executable makefile and 
generated stubs and interfaces) is gained by an interference mechanism 
that uses partitioning. Module assertions are converted to prolog 
statements. Based on configuration rules, partitions are created....

Finally in the construction phase an executable is generated by running 
the makefile that polygen has created in the generation phase.

Partitioning:
Partitions are sets of compatible components. They can be represented by 
directed, acyclic graphs,whose internal nodes represent integration 
methods and temrinal nodes represent source components.
Valid partitioning: has only a single root.

Weaknesses:
- source code must be changed and recompiled
- right now only for Polylith-TCP/IP
- data-conversion relies on underlying communication tool 
- good for putting together inhouse modules
- rather targeted at smaller modules
- no optimization, scheduling etc...