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IFIP WG 1.3 Referees' report on CASL



I wrote (on cofi-list):

> Tentative approval of CASL
> __________________________
> 
> IFIP WG 1.3 has TENTATIVELY APPROVED the proposed design for CASL!
> 
> The approval is subject to reconsideration (by the Language Design
> task group) of some aspects of the proposed design, as detailed in a
> formal referees' report.  The referees' report itself is to be made
> available (and announced on the cofi-language mailing list) later this
> week.  

The referees' report is now available by WWW and FTP:

  http://www.brics.dk/Projects/CoFI/Documents/CASL/RefereeReport/
  ftp://ftp.brics.dk/Projects/CoFI/Documents/CASL/RefereeReport/

The start of the document is appended.  

On behalf of CoFI: many thanks to the IFIP WG 1.3 referees for their
constructive and very helpful report on the design of CASL!

Just a reminder:

> Some of us have already looked at a draft of the report, and
> discussed the issues that were raised in it; we believe that they can
> all be resolved satisfactorily - without an excessive amount of
> further work on the CASL design...
> 
> The aim is for the Language Design task group to formulate an initial
> response to the referees' report straight away, before the end of
> June; a draft will be made available next week.

----   --------------------------------------------
\  /  | Peter D Mosses         <pdmosses@brics.dk> |
CoFI  | Common Framework Initiative  - Coordinator |
/  \  | WWW URL: http://www.brics.dk/Projects/CoFI |
----   --------------------------------------------


                           Referee Report on CASL

                        Hartmut Ehrig (Coordinator)
                               José Meseguer
                               Ugo Montanari
                              Fernando Orejas
                               Peter Padawitz
                         Francesco Parisi-Presicce
                               Martin Wirsing
                                 Uwe Wolter
                               (IFIP WG 1.3*)

                               June 6/11, 1997


Abstract

     This referee report is based on the presentation of CASL (Common
     Algebraic Specification Language) within CoFI (Common Framework
     Initiative) at the IFIP WG 1.3 Meeting on June 2 and 3, 1997, in
     Tarquinia. The presentation of CASL included the rationale,
     language design features concerning Basic, Structural and
     Architectural Specifications, and Libraries, abstract and concrete
     syntax and a brief overview of main parts of the semantics. For
     most of these aspects carefully written papers were available
     already before the meeting, especially the rationale of CASL, or
     were presented during the meeting e.g. the incomplete draft
     semantics paper.

     During the discussion at the IFIP Meeting it was suggested that a
     group of referees should be built up in order to provide an
     official IFIP WG 1.3 referee report. This report should be
     presented as quick as possible, preferably within the same week
     during the ADT Workshop, in order to allow a feedback between the
     referees and the authors of CASL. Unfortunately most of the
     referees were not able to read the rationale of CASL resp. other
     CASL papers before the meeting. Hence it was agreed that the
     referee report should be mainly based on the presentations and
     discussions during the IFIP meeting in order to avoid a time delay
     which would have been necessary to study all the CASL papers in
     sufficient detail.

Contents

   * 1 General Opinion

   * 2 General Guidelines for Revision
        o 2.1 Strong Algebraic and Categorical Flavor
        o 2.2 Theory of Algebraic Specifications and Semantics
        o 2.3 Relationship to Well-Established Algebraic Specification
          Languages

   * 3 Specific Recommendations
 
       o 3.1 Basic Specifications
             + 3.1.1 Empty Carriers
             + 3.1.2 Existential and Strong Equality
             + 3.1.3 Based Specifications
             + 3.1.4 Morphisms as First Class Citizens
             + 3.1.5 Kernel Sublanguage
             + 3.1.6 Identification of different Sublogics

        o 3.2 Style of Semantics
             + 3.2.1 Alternative Institution Style Semantics
             + 3.2.2 Institution Independence of Semantics for Structural
               and Architectural Level
             + 3.2.3 Additional more Abstract Semantics for the Structuring
               Constructs
             + 3.2.4 Inconsistency versus Undefinedness of Semantics

        o 3.3 Structural and Architectural Specifications
             + 3.3.1 Generic Specifications versus Architectural
               Constructions
             + 3.3.2 Pushouts versus "Almost Pushouts"

        o 3.4 Concrete Syntax

   * Footnotes

1 General Opinion

The general aim of CoFI and CASL to present a common algebraic specification
language with methodology and tool support, which includes the best of all
the existing algebraic specification languages is strongly supported by the
referees. In the opinion of the referees the resulting language must be
expressive and simple enough such that it is not only competitive with other
existing algebraic and non-algebraic specification languages, but also
superior with respect to specific aspects. The referees are aware that it is
a very difficult but important task to achieve this aim, because there is a
considerable diversity of different algebraic approaches and languages with
important theoretical and practical results which have been developed within
the last two decades by a wide spread algebraic specification community.
Taking into account these difficulties the authors of CoFI and CASL have
done an excellent job which is a very good basis to achieve the aims
mentioned above. For this reason the referees support the tentative approval
of CASL and recommend a revision according to the following general
guidelines and specific recommendations.

[...]

(*)
     IFIP Working Group 1.3, Foundations of System Specification

----------------------------------------------------------------------------
CoFI Document: CASL/RefereeReport --Handwritten/Typed Version,
Tarquinia/Berlin-- June 6/11, 1997.
Comments to ehrig@cs.tu-berlin.de