Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!tut.cis.ohio-state.edu!ucbvax!dan%@@uunet.UU.NET
From: dan%@@uunet.UU.NET (Daniel Cohen)
Newsgroups: comp.sys.transputer
Subject: Re: STRAND88
Message-ID: <9002130010.AA02911@>
Date: 13 Feb 90 00:10:52 GMT
Sender: usenet@ucbvax.BERKELEY.EDU
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Lines: 85


Nick Rothwell writes:
	Well, I use the term dataflow language to refer to those simple-minded
	antiquated languages which only have integers and single-assignment. I
	think any "real" modern language has a user-extensible type system and
	a fair degree of polymorphism such that you can do "dataflow" on
	objects of any type; then, you start getting into problems with
	structured objects going out of scope, and garbage collection and so
	on.

STRAND88 does have a user-extensible type system, and
is polymorphic, as discussed below: 

	>	What sort of type system does the language have? Polymorphic? Dynamic?
	>
	>Polymorphic

	Good. Is there a formal type semantics?

You lost me here! Are you asking for a formal semantics
for Strand ( denotational semantics or VDM etc. ) ?

	>	Does it address the problems associated with programming in the
	>	large (modules, interfaces, abstraction)? - or is that outside its
	>	scope?
	>
	>There is a module system which is smart enough
	>to load modules automatically when they are required.
	>...
	>We liked Strand because it seemed like a good language
	>to build up on - object-oriented systems; rule-based
	>systems etc. but most of this work is still at a conceptual
	>level ( except objects ). There's also been a lot of work
	>done on programming methodologies which should eventually
	>result in some dataflow and/or object-oriented CASE tools.

	That's not exactly what I meant; for large systems you want to be able
	to construct interface specifications containing abstract types, and
	have a way of matching these to actual implementations. For a proper
	object-oriented system, you need (multiple) inheritance, and from here
	the type semantics starts to get a little hairy. The problem with
	Prolog and the like is the lack of scoping of declarations, which is a
	serious drawback IMHO.

Hmmm. I think you do need a copy of the Foster and Taylor book
to answer your questions 'cos I'm still not sure I understand
them! As for inheritance; I should distinguish between raw
Strand ( at which level Strand processes can be construed as
proto-objects ) and something built in Strand ( StOOPS ?!? ).
In the former case, there is no inheritance: objects can feed
any other arbitrary object with their leftovers. In the latter
case, any inheritance or delegation scheme you care to think up
can probably be coded in Strand very easily since the language
is designed for manipulating streams. For some reading on the
low-level interpretation of Strand processes as objects, try
"Objects - A Fresh Look" by Xerox PARC's Ken Kahn
( ECOOP 89 proceedings ); you might also like to read:
"Money as a Concurrent Logic Program" by Ken Kahn and
William Kornfeld ( NACLP 89 proceedings ).  


	On a more general note: how much take-up do you expect there to be for
	a new language in a world dominated by Fortrash, C, and to some extent
	Occam? Just curious how much of a commercial risk this is, since I'm
	mostly involved in the academic side of language research.


That's partly up to people like you! The language model is
interesting enough to get lots of academics involved, but
it's not just interesting - there are significant benefits
to a programmer in using Strand. Fortran and C will,
of course, continue to have the lion's share of scientific
and general-purpose computing; but they are not well suited
to parallel processing - Strand is. Research at
Argonne National Laboratory makes it clear that bilingual
( or multilingual ) programming will be of great importance
in the application of parallel systems.

Daniel Cohen
Strand Software Technologies Inc.
15220 NW Greenbrier Parkway, Suite 350
Beaverton, OR 97006, USA
Tel: +1 (503) 690 9830

e-mail: dan%ssti@uunet.uu.net  or  uunet!ssti!dan