[CoFI] Minutes of Amsterdam Meeting on Language Design

[Christine.Choppy@irin.univ-nantes.fr]

CoFI LANGUAGE DESIGN Task Group Meeting

Amsterdam, September 27, 1997


Minutes written by Christine Choppy and Peter Mosses.

Participants:

Hubert Baumeister (HB)
Jan Bergstra (JB)
Didier Bert (DB)
Michel Bidoit (MB)
Peter Borovansky (PB)
Christine Choppy (CC)
Helene Kirchner (HK)
Bernd Krieg-Brueckner (BKB)
Karl Meinke (KM)
Peter Mosses (PM)
Christophe Ringeissen (CR)
Mark Van den Brand (MVB)
Frederic Voisin (FV)

AGENDA:

- Compromise concrete syntax
- Reconsideration of language design issues

See the URL http://www.brics.dk/Projects/CoFI/Documents/CASL/ for the
current versions of the various documents concerning CASL.


I) Concrete Syntax:

A single proposal for concrete syntax for basic specs is agreed upon,
eliminating the need for a verbose and a concise style but keeping the
distinction between input and display.

As announced after the meeting,the updated concrete syntax proposal is
now available at:
http://www.brics.dk/Projects/CoFI/Documents/CASL/SyntaxIssues
(deadline for comments: Monday October 20th).

The Paris group will summarize the alternatives for their previous
proposal regarding structured specs, which is a matter of urgency.


II) Reconsideration of language design issues:

Function attributes FUN-ATTR were discussed: it is agreed to propose
turning them into a kind of AXIOM, separating this from FUN-DECL
again.

The remaining discussion focussed on the points listed in App. D of
the CASL Summary (v0.98):

* (1.2, 2.2) Are empty carrier sets to be allowed or not?  Are there any
  interesting examples where it makes a difference?

No.  No.  The arguments for and against are summarized in a message
by Till Mossakowski [cofi-language, 21 Sep 97].  The meeting agreed
with the arguments, but not with Till's (slightly) favoured conclusion.

* (2.1.4) The abstract syntax of a COMPONENT has been generalized to
  allow several selector functions with the same result sort to be
  specified together.

Agreed.

* (4.1) The abstract syntax and semantics of ISO-DECL have been adjusted
  to be more uniform to those of SUBSORT-DECL. Are there any objections?

None were raised.

* (footnote 6) Can the treatment of compound identifiers be adjusted to
  permit a fully institution-independent treatment of structuring
  constructs?

See Till's message for a presentation of the (rather technical)
issues.  The meeting agreed to leave the matter to the Semantics task
group. 

* (footnote 7) What abstract syntax is to be used for making explicit
  which parts of the parameter signatures may share with the body of the
  generic specification, so as to obtain pushout semantics?

A proposal is currently being prepared by MB and Andrzej Tarlecki.

* (5) Should naming of morphisms be allowed? See Note L-6, which
  also proposes changing the treatment of instantiation and sharing.

DB presented the three levels of his proposal.  The meeting agreed to
incorporate the first level in CASL, allowing morphisms to be named in
libraries and used in instantiation of generic specifications.  The
further levels were thought to be too radical (semantic and
methodological aspects were discussed), and left to potential
extensions of CASL.

* (8.2) What changes are needed to the abstract syntax for UNIT-TERM?

A proposal is currently being prepared by MB and Andrzej Tarlecki.

The meeting finished at 7pm.  Thanks to Mark van den Brand (University
of Amsterdam) for making the local arrangements, and to Paul Klint
(CWI) for sponsoring the CoFI meetings in Amsterdam.


NEXT MEETING

It is planned to hold further meetings in Bremen in early January,
1998, together with Tools and Methodology meetings.  Details and a
registration form will be sent later this month to the general CoFI
mailing list, cofi-list@brics.dk.

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Christine Choppy   tel:(+33 2)/(02) 40 37 49 54 -fax:(+33 2)/(02) 40 37 49 70
IRIN - Universite de Nantes & Ecole Centrale
2, rue de la Houssiniere, BP 92208, F44322 Nantes Cedex 3, FRANCE
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