[plt-scheme] ipc among mzscheme processes

I ran across the DTYPE protocol awhile back.  But this wheel has been
chipped from stone many times in ancient BX times (Before XML)
I think its history is something like this:

- MIT Media Labs developed a great deal of software in Lisp.
- There was shock and dismay in that no one seemed to use it.
- Reason: they were Lisp, the rest of the world was C.
- DTYPE protocol was to expose Lisp based software to C.

The FramerD site has Java, Python and C libs in various states of
maturity.

Its claims include: 

"DTypes are a portable data representation used throughout the FramerD
suite of libraries, tools, and applications. There are two basic levels
to the DType representation: a minimal set of "core data types" and an
extensible external binary representation for those types and their
extensions. Applications and libraries use and extend the native data
types, taking advantage of communication, persistence, and indexing
facilities which use the external representation.

DTypes differ from other data sharing approaches in not depending on
explicit data declarations for sharing complex structures. Distributed
processing models like CORBA rely on shared data declarations for
communicating complex data structures. DTypes allow a `sloppier'
approach where basic data types include nested and labeled heterogenous
structures. This allows for fast prototyping of applications and
protocols as well as their on-line extension."

http://framerd.sourceforge.net/docs/concepts.html#dtypes

Ray Racine