Danny Amor's Online Library/Danny Amor's Online Library - Volume 1.iso/html/faqs/faq/object-faq/part10

Text File | 1995-07-25 | 33.7 KB | 958 lines

Subject: Comp.Object FAQ Version 1.0.7 (10-27) Part 10/10
Newsgroups: comp.object,comp.answers,news.answers
From: Bob Hathaway <[e-mail]>
Date: 29 Oct 1994 11:43:19 GMT

Archive-name: object-faq/part10
Last-Modified: 10/27/94
Version: 1.0.7

>62  Amadeus, persistence

From: [e-mail] (Aoife Cox)
Subject: Re: In Search of Persistence
Date: 14 Dec 1993 20:04:38 +1100
Organization: University of Western Sydney

>I have been searching the net trying to find any locations for papers about
>implementation of persistence object systems or about persistence and OOPL.  As
>yet, I have not found anything remotely related.

>Are there any ftp sites with such papers that someone can direct me to?
There should be some papers on the Amadeus system, developed by the
Distributed Systems Group at Trinity College, Dublin, ftp-able from
ftp.cs.tcd.ie. Look in the /pub/tcd/tech-reports directory....

Hope this helps.

Aoife


>63  Chorus,Dist,RT,MicroK

From Marc Maathuis ([e-mail]):

You may want to take a look at CHORUS, a distributed real-time
microkernel that can be combined with the CHORUS/MiX subsystem, which
is a modular, fully compatible UNIX System V (R3.2 or R4.0)
implementation.  There is also an OO subsystem named COOL (CHORUS
Object Oriented Layer). CHORUS runs on i386/i486, 680x0, SPARC,
transputer and on several other processors.

CHORUS is available as a source technology. In Jan 94, SCO and Chorus
will release a *binary* product for the PC market: "CHORUS/Fusion for
SCO UNIX" is binary compatible with SCO UNIX and offers real-time
functionality (POSIX 1003.1b and .1c, i.e. the former .4 and .4a
interfaces) and clustering functionality.

COOL provides a distributed OO programming environment for
C++.  COOL supports a set of system calls that allow the creation of
dynamic objects. These objects can be sent messages in a location
transparent way, they can be migrated between address spaces and sites
and they can be stored in a persistent store; this is done in a
transparent way, as an extension of the C++ language.

There are several technical reports (in PostScript format) on CHORUS
and on COOL available via anonymous FTP from Chorus systemes, France:
ftp.chorus.fr [192.33.15.3], directory pub/chorus-reports. See the file
"index" for an overview.

There is also a set of ~90 slides on Chorus and CHORUS available in
the directory pub/chorus-slides/CS-TR-92-64 (PostScript, versions 1-up
and 2-up).

If VTT is a public research lab, then you might be interested by the fact
that Chorus systemes has special programs for universities. For more
information on offering, conditions, etc, ftp to ftp.chorus.fr and get
the following ASCII files
   - pub/README
   - pub/academic/README
   - pub/academic/offerings
If you have questions, you may contact Didier Irlande <[e-mail]>
for license issues or Xavier Galleri <[e-mail]> for technical
issues.


>64  Self Opt.

From: [e-mail] (Urs Hoelzle)
To: [e-mail]
Subject: thesis available for ftp
Date: Fri, 2 Sep 94 11:15:29 PDT
Reply-To: [e-mail]

Dear self-interesters,

My thesis is now available via ftp and Mosaic (see below).  Yes, I
have graduated!  Though many things will change, I'm planning to keep
on working on Self at UCSB; my new e-mail address is [e-mail].
However, I am no longer maintaining the self-interest list, for
questions/requests please contact self-request@self rather than
writing directly to me.

-Urs

---------------

Urs Hoelzle. "Adaptive Optimization for Self: Reconciling High
Performance with Exploratory Programming." Ph.D. thesis, Computer
Science Department, Stanford University, August 1994.

The report is available in PostScript form via ftp from
self.stanford.edu:/pub/papers/hoelzle-thesis.ps.Z or via Mosaic from
http://self.stanford.edu.  In a few weeks, it should be available in
printed form as a Stanford CSD technical report and as a Sun
Microsystems Laboratories technical report.

Abstract: Crossing abstraction boundaries often incurs a substantial
run-time overhead in the form of frequent procedure calls.  Thus,
pervasive use of abstraction, while desirable from a design
standpoint, may lead to very inefficient programs.  Aggressively
optimizing compilers can reduce this overhead but conflict with
interactive programming environments because they introduce long
compilation pauses and often preclude source-level debugging. Thus,
programmers are caught on the horns of two dilemmas: they have to
choose between abstraction and efficiency, and between responsive
programming environments and efficiency. This dissertation shows how
to reconcile these seemingly contradictory goals by performing
optimizations lazily.


>65 ORBELINE: CORBA

PostModern Computing is making its CORBA-compliant ORBeline product
available free of charge to the academic community for teaching and
research purposes.  ORBeline is available via anonymous ftp from
labrea.stanford.edu under pub/pomoco.

We are making the SunOS 4.x, Solaris 2.3, and OSF/1 versions of
ORBeline available.  We will consider making other platforms available
as well if there is enough interest.

Suresh Challa
PostModern Computing
[e-mail]

What follows is the README file of this release:

-------------------------------------------------------------------------------

                                ORBELINE
                                --------

                    The SMART Object Request Broker


ORBeline is a complete implementation of OMG's Common Object Request
Broker Architecture (CORBA).  ORBeline goes beyond the standard
specification to provide a SMART communication framework allowing
you to easily develop large distributed applications that are robust,
scalable, flexible and maintainable.  ORBeline incorporates PostModern's
proven communication framework that links thousands of nodes.

Highlights
----------

ORBeline's SMART Agent dynamically tracks the communication taking place
between all objects and their clients:

   o Smart Binding and Protocol Selection

     ORBeline automatically picks the best communication mechanism as
     soon as you try to access an object.  If the object is in your process,
     it bypasses the ORB and the network altogether.  When the object is on
     a remote node, ORBeline's SMART and efficient on-the-wire protocol
     is selected.  When the object is implemented using another vendor's
     ORB, that vendor's on-the-wire protocol is used.

   o Built-in Fault Tolerance

     ORBeline's SMART Agent monitors communication between objects and their
     clients.  In case of a failure, the SMART agent and ORBeline cooperate
     to reestablish connections between processes or their replicas.

   o Dynamic Directory Service

     ORBeline's Dynamic Directory Service tracks all registered and active
     objects, providing a high degree of efficiency, total location
     transparency and easy administration.  There is no need for
     cumbersome configuration files, and no need for heavyweight object
     migration and replication mechanisms.

   o Platforms

     ORBeline runs on all classes of computers ranging from Cray
     supercomputers, to workstations, to personal computers and
     embedded systems.

Complete CORBA implementation
-----------------------------

ORBeline is the most complete ORB implementation currently on the
market.  It features the following:

   o IDL Compiler implementing the entire Interface Definition
     Language.

   o Static and Dynamic Invocation Interfaces

   o Complete Interface and Implementation Repositories.

   o Support for Object Activation.

   o Complete set of object administration tools.


Features
--------


   o High Performance and Low Overhead

     ORBeline provides high performance while adding little overhead
     to your application.  ORBeline is the only ORB product available
     on the market today suitable for running on real-time, embedded
     systems.

   o Flexible and Easy to Use

     With ORBeline it is easy to develop, deploy and maintain large
     distributed applications.  ORBeline provides a high degree of
     flexibility and takes care of cumbersome details allowing
     developers to focus on their applications.

   o WAN Connectivity

     ORBeline uses PostModern's proven communication technology to
     connect wide area networks.

   o Scalability

     ORBeline's smart use of network resources and communication protocols
     allows applications to scale to networks of thousands of nodes.

   o Object Migration and Replication

     ORBeline's SMART agent and Dynamic Directory Service allow easy object
     migration and replication.


Platforms
---------

We are making the SunOS 4.x, Solaris 2.3, and OSF/1 versions of
ORBeline available free of charge to the academic community.
We will consider making other platforms available as well if there
is enough interest.

The following compilers are supported in this release:

Solaris 2.3:    Sun C++ 4.0 (native), SparcWorks 3.0
SunOS 4.x:      Sun C++ 3.0 (cfront), SparcWorks 2.0.1
OSF/1 1.3:      DEC C++

If there is enough interest, we can make versions compatible with
other compilers available as well.


LICENSING
---------

ORBeline is provided free of charge to the academic community for
teaching and research purposes.  After installing ORBeline, call us at
[phone] or send e-mail to [e-mail] and we will send you
a perpetual license for your site.

If you are interested in ORBeline for commercial purposes, contact us
and we can provide a limited time evaluation license.


ACKNOWLEDGEMENTS
----------------

We would like to thank Stanford University for providing us with
a high-speed ftp site from which to distribute this ORBeline
release.



                    PostModern Computing Technologies, Inc.
                            1897 Landings Drive
                          Mountain View, CA  94043
                             Tel: [phone]
                             Fax: [phone]
                               [e-mail]


>66 OO Designer CASE Tool

       **************** Object Oriented Designer ***************

            Prof. Taegyun Kim [[e-mail]]
              Pusan University of Foreign Studies
                  Pusan, Korea

                 Version : Version 1.3.1
                 Revised : October 6 1994

       *********************************************************

Let me introduce myself. I am an assistant professor working at Department of
Computer Engineering in Pusan University of Foreign Studies which resides in
Pusan, Korea. My major interest is in software engineering especially in the
area of object oriented methodologies. In teaching courses in systems analysis
and software engineering I found a need for a good case tool that could be used
by my students. Unfortunately, commercial case tools are too expensive for a
university to purchase so I developed OOD. I have spent 17 man months building
OOD. Because this is my first project combining object oriented methods, Motif,
and C++, some of the source code may be a little clumsy. However, it does work
well and it is still evolving.  This project is very hard but is also very
interesting. Let's enjoy it together.

P.S.: I am anxious for your criticism or comment on this product. So, if it
works on your system, please respond to me with even a one line (very short)
message.  It will give me some encouragement. Moreover please inform me your
status (student, professor etc.) if possible.

-Taegyun Kim

             --------------- Contents --------------
                     0. Summary
                     1. System Environment
                     2. Building OOD
                     3. Initializing the Working Environment
                     4. Functions
                     5. Examples
                     6. Reference Books
                     7. Cautions
                     8. FAQ
            ----------------------------------------

0. Summary
----------

The Object Modeling Technique [OMT] by James Rumbaugh et al. is a methodology
for object oriented development with a graphical notation for representing
object oriented concepts.  Object Oriented Designer [OOD] is a case tool for
constructing the object diagrams defined in OMT. In order to use OOD it is
necessary to understand OMT and its graphical notation. See reference (2).

Why "OMT"? OMT evolved from the Extended Entity Relationship [EER] model which I
have studied since the mid 80's. There are a number of other approaches to
expressing object oriented concepts but I believe that OMT is superior to most
of these. Yourdon's Object Oriented Analysis [OOA] notation, for example, is
another excellent approach to the problem but has some limits in functionality,
particularly with respect to data modeling, that are present in OMT.

Currently, OOD has following primary functions:

    - general graphics editor (with limited functionality)

    - object diagram layout (with some additions w.r.t. original OMT notation)

    - C++ code skeleton generation (header file + source file)
      The comments and codes for individual member functions can be documented,
      or edited within OOD directly.
      The C++ code generator supports inheritance.

I have attempted to make OOD as user-friendly as possible. My students learn to
use it in a day even without a manual. The user-friendliness of OOD is due to my
own object oriented, user interface mechanisms.

Currently OOD generates a C++ code skeleton from an object diagram.  I have a
short term final goal to develop an object oriented "environment" with
flexibility and portability. I think that about additional 20 man months effort
could lead me to the final goal. Because I am currently working very hard to
enhance its functionality, I am not especially concerned with system portability
issues at the moment so building OOD on your particular platform may require a
little work on your part. Please inform me of any changes that you need to make
to build OOD on your system.


1. System Environment
---------------------
OOD was built on a SPARC station running OS4.1.x, X11-R5 and Motif-1.2 and
C++-2.0. OOD has also been successfully built on a SPARC using gcc-2.5.8 and
libg++-2.5.3. It should build on most UNIX systems with X11-R5, Motif-1.2 and a
"reasonable" C++ compiler.

2. Building OOD
---------------------
    1) In ood directory edit the Makefile to reflect your environment
    2) run "make depend"
    3) run "make"

3. Initialize Working Environment
--------------------------------
OOD requires the user to select a working repository in which to store various
output files. If this is the first time you are running OOD:

    1) point at the top-menu,
    2) select "Environment",
    3) select "Setup",
    4) define your working repository.

If a working repository has been previously defined, select it:

    1) point top-menu
    2) select "change to"
    3) set your working repository

  ...


>67 OOTher OO CASE Tool

From: [e-mail] (Roman Zielinski TT/TSM)
Subject: CASE OOTher 1.06f released (free/shareware)
Organization: Ericsson
Date: Tue, 20 Sep 1994 07:15:09 GMT

Product:
    OOTher
    OO Documentation & CASE Tool Release 1.06f

Environment:
    MS-Windows 3.1

Short description:
    The tool is a complete documentation development package for
     the following methods/notations:
    - Peter Coad's OOA method (Coad/Yourdon)
    - State Machine diagrams using a subset of SDL
    - allocation of objects to processors and processes
    - Use Case diagrams and Object Interaction diagrams
      as proposed by Ivar Jacobson in his OOSE book

    The tool also performs verification of consistency between the
    diagrams, and by direct coupling assures for consistent naming
    of objects and methods/services.

    The tool is build around 5 easy to use graphic editors and is
    capable of documenting all objects, their attributes, services
    and also associations between objects.

    Each service may have a state machine (FSM) diagram.
    C++ Headers may be generated automatically from the OOA diagram -
    it assures consistent naming of member functions and attributes.
    The applied mark-up notation for C++ headers should be powerful
    to give compiler ready headers for at least 80% of applications.

    For a better integrability with other windows applications and to
    allow esthetical control, the tool allows free font selection and
    a copy-paste transfer of diagrams via clipboard in meta file format
    to e.g. Word for Windows 2.0.

    The resulting file is ASCII with open & documented format,
    i.e. it's easy to add own utilities for data extraction.

    Complete user documentation is attached in form of a hypertext
    windows-help file.

    The tools distributed as:
    - freeware for students, schools and home users
    - as shareware for others (USD $170 for corporate 1-5 user license).
    - free upgrade form 1.0x to 1.06f for registered users if they
      fetch files from e.g. SimTel Software Repository
    - free evaluation in 4 weeks

    - an evaluation copy may be ordered from the author (USD $70,
      rest of the license fee if/when you register)
        Roman M. Zielinski
        Tre Kaellors Vaeg 7
        S-145 65 Norsborg
        Sweden
      (You may also reach me at [e-mail] until July-94)

*****   Version 1.06f contains bug corrections and updates of zoom-handling.
                Roman M. Zielinski
                [author]

----------------------------------------------------------------------
SimTel id:
pub/msdos/windows3/
oot-106f.zip    OOTher OO Doc Tool 1.06f CASE OOA+OOSE
----------------------------------------------------------------------
mail a message
To: [e-mail]       (***se below, for other internet server names***)
Subject: SimTel-request
Body:
/PDGET MAIL /SimTel/msdos/windows3/oot-106f.zip uuencode

(some TRICKLE-servers don't like the arguments 'MAIL' and 'UUENCODE', so
thay may need to be omitted. Thay also may need the old path specification,
example for the Swedish TRICKLE:
/PDGET <msdos.windows3>oot-106f.zip
)

You may also use Archie to find sites storing OOTher.
Instructions for archie and paths for OOTher can be fetched via e-mail
from e.g. [e-mail]
with a body:

Help
find oot

[... On Simtel Retrieval ...]

or fetch via anonymous ftp or ftpmail from OAK.Oakland.Edu
/SimTel/msdos/windows3

or its mirrors:

St. Louis, MO:  wuarchive.wustl.edu (128.252.135.4)
  /systems/ibmpc/msdos
Corvallis, OR:  archive.orst.edu (128.193.2.13)
  /pub/mirrors/oak.oakland.edu/simtel20/msdos
Falls Church, VA:  ftp.uu.net (192.48.96.9)
  /systems/ibmpc/msdos/simtel20
Australia:  archie.au (139.130.4.6)
  /micros/pc/oak
England:  src.doc.ic.ac.uk (146.169.2.1)
  /pub/packages/simtel20
Finland:  ftp.funet.fi (128.214.6.100)
  /pub/msdos/SimTel-mirror
Germany:  ftp.uni-paderborn.de (131.234.2.32)
  /msdos
Israel:  ftp.technion.ac.il (132.68.1.10)
  /pub/unsupported/dos/simtel
Switzerland:  ftp.switch.ch (130.59.1.40)
  /mirror/msdos
Taiwan:  NCTUCCCA.edu.tw (140.111.1.10)
  /PC/simtel
Thailand:  ftp.nectec.or.th (192.150.251.32)
  /pub/mirrors/msdos

----------------------------------------------------------------------
To run ftpmail send e-mail to e.g. [e-mail]
with the message body:

connect ??hostname??
binary
uuencode
cd pub/msdos/windows
get oot-106f.zip
quit
----------------------------------------------------------------------


>68 OS Papers (OO?)

From: [e-mail] (Arindam Banerji)
Newsgroups: comp.object
Subject: The Paper Trail database
Date: 21 Sep 1994 14:39:20 GMT
Organization: University of Notre Dame

            THE PAPER TRAIL

The "Paper Trail" - an experimental database of ftp'able OS papers
is now available through http://pclsys64.dcrl.nd.edu/papers. This
database allows users to find and access papers that are available for
ftp on the internet. We have initially populated this database with
about 5500 entries. Most of these entries reflect our own area of
interest, that is Operating Systems and related areas. We'll add
entries to the database from time to time. However, it'll probably
be very difficult to keep this up-to-date without help from other
users of this database. Hence, the database provides any user the added
facility to submit entries.

We hope that the xmosaic interface to this database is intuitive and
simple. If you have any suggestions and criticisms, please do let us
know - including how this compares with other such services.


-----------------------------------------------------------------------------
Arindam Banerji                             Michael Casey
            384 FitzPatrick Hall
           Dept. of Computer Science and Engineering
          University of Notre Dame
(219)-631-5772    Notre Dame, IN 46556       (219)-631-5273
[e-mail]                        [e-mail]


>69 Trellis

From: [e-mail] (Bruno Achauer)
Subject: Trellis compiler available
Date: 23 Oct 1994 00:16:02 GMT
Organization: Telematics Department, Karlsruhe University, Germany

The beta release of version 0.2 of the TNT Trellis system is now
available for anonymous ftp from tk.telematik.informatik.uni-karlsruhe.de.

Enclosed is ANNOUNCE file from the distribution:

What are Trellis and TNT
~~~~~~~~~~~~~~~~~~~~~~~~

Trellis is an object-oriented language developed within Digital
Equipment Corp. The language features compile-time type checking,
multiple inheritance, parametrized types, exception handling and
iterators.


TNT is a new implementation of Trellis, consisting of a compiler, a
library of predefined types and a (rudimentary) run time system:

  - The compiler implements the language as defined by the reference
    manual (except for a few esoteric constructs), plus a few minor
    extensions.

  - Predefined types are standard types such as integers, strings,
    arrays etc. (in Trellis, no type is built into the language!),
    an IO system and a (rudimentary) hierarchy of collection types.

  - The run time system is pretty incomplete right now; in particular,
    neither garbage collection nor threads are implemented yet.

The system is available for several architectures:

  - the Digital Alpha (running OSF/1),
  - the HP Precision Architecture (under HP-UX),
  - the Intel 386 (under Linux),
  - Digital's Mips workstations,
  - Sun's Sparc workstations (running SunOS).

Both source code and prebuilt kits are available.

Further work will concentrate on supporting transparently distributed
objects a la DOWL.


Changes since last version
~~~~~~~~~~~~~~~~~~~~~~~~~~

* The HP-PA, Linux and Sparc ports.

* Building the compiler no longer requires the SFIO library.

* The compiler now can use the GNU assembler to generated object files;
  at least on small MIPS machines, this will speed up compilation
  considerably.

* Several minor bugs have been fixed.


Requirements
~~~~~~~~~~~~

The prebuilt kits require disk space ranging from 800 KB (Linux) to
2.4 MB (OSF/1); a C compilation system (assembler, linker and the C
library) must be installed. In addition, the Mips and HP-PA versions
will benefit if the GNU assembler is present.

Building the system from scratch requires from 5.2 MB (Linux) to 16 MB
(Alpha). You will also need some auxiliary tools and libraries:

  - Cocktail V9208 (the Karlsruhe Compiler toolbox),
  - GNU make V3.68 or later,
  - patch,
  - makedepend.

Most of these should be available on a nearby ftp site (makedepend is
part of the X distribution; GNU make and patch are distributed by the
FSF).

Cocktail is available from several ftp sites, but most of the versions
floating around will not work on the Alpha. A patched version is
available on tk.telematik.informatik.uni-karlsruhe.de (see below).

If you plan to build the MIPS or the SPARC version, you will also need
the GNU C compiler.


How to get it
~~~~~~~~~~~~~

A source kit is available via anonymous FTP from

    tk.telematik.informatik.uni-karlsruhe.de (129.13.3.200)
    file directory /pub/tnt/tnt-0.1.tar.gz.

There are also some additional kits in the same directory:

    * doc    -- PostScript versions of DEC-TR-372 (language
           reference manual) and DEC-TR-373 (language primer).

    * prebuilt    -- binary kits.

    * tools    -- source kits for Cocktail.


Please direct bug reports, requests, comments etc to

    [e-mail].


Acknowledgements
~~~~~~~~~~~~~~~~

The development of TNT has been supported by Digital Equipment's
Campus-based Engineering Center in Karlsruhe.

Special thanks to Jean Fullerton and Lutz Heuser at Digital for
making the technical reports available.


Copyright
~~~~~~~~~

Copyright © 1994, Universität Karlsruhe, Germany; parts Copyright © 1994
Digital Equipment Corp, Maynard, Mass.

The TNT Trellis software, both binary and source (hereafter, Software) is
copyrighted by Universität Karlsruhe, Germany (UKA), and ownership
remains with the UKA. Parts of the software are copyrighted by Digital
Equipment Corp., Maynard, Mass.

The UKA grants you (hereafter, Licensee) a license to use the Software
for academic, research and internal business purposes only, without a
fee.  Licensee may distribute the binary and source code (if released)
to third parties provided that the copyright notice and this statement
appears on all copies and that no charge is associated with such
copies.

UKA MAKES NO REPRESENTATIONS ABOUT THE SUITABILITY OF THIS SOFTWARE FOR
ANY PURPOSE.  IT IS PROVIDED "AS IS" WITHOUT EXPRESS OR IMPLIED
WARRANTY.  THE UKA SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY THE
USERS OF THIS SOFTWARE.

--
--Bruno.

---------------------------------------------------------------
| Bruno Achauer, U of Karlsruhe, Telecooperation              |
| Kaiserstr. 12, D-76128 Karlsruhe, Germany                   |
| [e-mail]              |
| Phone [phone], Fax [phone]                   |
---------------------------------------------------------------

>70 CooL-SPE

From: [e-mail] (Dr. Gerhard Müller)
Subject: Announcement of the CooL Software Production Environment
Date: Tue, 25 Oct 1994 11:42:28 UNDEFINED
Organization: Sietec Systemtechnik

        ANNOUNCEMENT

The CooL-Software Production Environment - a new object-
oriented development environment in Public Domain

The CooL-SPE is a modern software production environment
for the development of object-oriented application systems
supporting grafical user interfaces and relational database
technology. In the landscape of existing software production
technologies the CooL-SPE is more closely settled to 4GL
environments than to the usual C++ environments, mostly
more dedicated to system programming. The CooL-SPE was
developed by Siemens Nixdorf Informationssysteme (SNI)
within the ESPRIT project ITHHACA and is used since in a
number of large projects.

Allthough the CooL-SPE as a programming environment is
functional quite rich, it is also very lean and thus comparable
fast to learn and reliable tu use. In one project, which we sup-
ported recently, we could learn that newly assigned engineers
to a fairly large project (400 classes with some 100.000 lines
of code) were able to learn the environment, to understand the
application and to become productive within a month - and
that without any practical experience on object-oriented pro-
gramming before.

The system has product quality and is implemented in major
parts in itself.

The CooL-SPE is available for Linux 1.0.1, Solaris 2.3 and
SINIX 5.41. You may receive the system (sources and docu-
mentation) via ftp.fu-berlin.de in the directoy /pub/unix/lan-
guages/cool.The file itself is named cool-2.1.tar.Z.

>71 Contra-/Co- Variance

From: castagna@oeillet (Giuseppe Castagna)
Subject: Paper on covariance and contravariance
Date: 25 Oct 1994 17:09:51 GMT
Organization: Ecole Normale Superieure

                            PAPER ANNOUNCEMENT
                            ==================

The following short (13 pages long) note


        "COVARIANCE AND CONTRAVARIANCE: CONFLICT WITHOUT A CAUSE"

                            Giuseppe Castagna
                Laboratoire d'Informatique de l'ENS, Paris


is available by anonymous ftp at ftp.ens.fr in the file
 /pub/reports/liens/liens-94-18.A4.dvi.Z

ADVERTISEMENT: This paper tries to explain
-------------

1. What covariance and contravariance serve for.

2. Why covariance and contravariance are not opposing views but both
   *must* be integrated in a *type-safe* formalism. I.e.: don't choose
   just one of them.

3. Where the "objects as records" analogy hides covariance.

4. How to type binary methods in the models based on the analogy "objects
   as records" (i.e. how to have ColorPoint < Point even if they respond
   to a message "equal")

5. How to have multiple dispatch when objects are modeled by (recursive)
   records.

6. Why all the previous points are strictly related one to each other.

                                 ABSTRACT

In type theoretic research on object-oriented programming the ``covariance
versus contravariance  issue'' is a  topic of continuing  debate.  In this
short note  we   argue that covariance  and   contravariance appropriately
characterize  two distinct  and  independent  mechanisms.    The so-called
contravariance  rule correctly captures   the {\em  substitutivity\/},  or
subtyping relation (that establishes which  sets of codes can replace {\em
in every context\/} another   given set).  A covariant relation,  instead,
characterizes the {\em specialization\/} of  code (i.e.\ the definition of
new code that replaces   the old one  {\em  in some particular  cases\/}).
Therefore,  covariance  and contravariance  are  not  opposing  views, but
distinct  concepts that each have   their place in object-oriented systems
and that  both   can  (and  should)  be type    safely  integrated in   an
object-oriented language.

We  also show  that   the  independence of    the two  mechanisms  is  not
characteristic of  a  particular model  but is  valid  in  general,  since
covariant specialization is present also  in  record-based models, but  is
hidden by a deficiency of all calculi that realize this model.

As an aside, we show that  the lambda&-calculus can  be taken as the basic
calculus both for an  overloading-based and for  a record-based model.  In
that  case, one not only obtains  a more uniform vision of object-oriented
type  theories but, in   the case of  the  record-based approach, one also
gains  multiple dispatching,  which   is  not  captured by   the  existing
record-based models.



APPENDIX F  MAGAZINES, JOURNALS AND NEWSLETTERS
===============================================

ACM
---
  OOPSLA - Association For Computing Machinery's yearly conference on Object-
    Oriented Programming Systems, Languages, and Applications.
    Addison-Wesley
    Order Dept.
    Jacob Way
    Reading, MA 01867
    [phone]
  ACM OO Messenger    - Quarterly on Object-Oriented Languages and Systems
  ACM SigPlan Notices - Special Interest Group on Programming Languages
    Publications Office
    ACM, 1515 Broadway
    NY, NY 10056
    [phone], FAX: [phone]
  Additional information can be obtained from [e-mail].

American Programmer (Yourdon's Newsletter)
------------------------------------------
Monthly Newsletter on Software Engineering including quality, the CMM, object-
oriented technology, and etc.  $395/year.  Send for complementary copy.
  American Programmer, Inc.
  Dept. 13
  161 West 86th Street
  New York, NY  10024-3411

CASE Trends Magazine
--------------------
Sorry, still no reference.

The Coad Letter
---------------
From Peter Coad (pronounced "Code"), of Coad/Yourdon OOA/D fame.
  Object International, Inc.
  3202 W. Anderson Lane, Suite 208-724
  Austin, TX  78757-1022
  Tel: [phone]
  Fax: [phone]

The C+@ Quarterly
-----------------
On the C+@ language (pronounced "Cat").
Unir Technology, Inc.
184 E. Shuman Blvd.
Naperville, IL 60563

DE FACTO - The ami Newsletter
-----------------------------
Reports on the progress of ami (application of metrics in industry).
  ami User Group
  Centre for Systems and Software Engineering
  South Bank University
  103 Borough Road, London SE1 OAA
  Phone: [phone]
  Fax:   [phone]

The Guerilla Programmer
-----------------------
For the practicing professional programmer.
  New, by Ed Yourdon.
  Phone:  [phone] or 617-648-9702
  Fax:    [phone] or 617-648-1950

HOTT-LIST - FREE NEWSLETTER
---------------------------
Free, electronic newsletter features article summaries on new generation
computer and communications technologies from over 100 trade magazines
and research journals; key U.S. & international daily newspapers, news
weeklies, and business magazines; and, over 100 Internet mailing lists &
USENET groups.  Each monthly issue includes listings of forthcoming &
recently published technical books and forthcoming shows & conferences.
Bonus: Exclusive interviews with technology pioneers.  E-mail
subscription requests to: [e-mail]  (Leave the "Subject" line
blank.)  In the body of the message, type: SUBSCRIBE HOTT-LIST (do not
include first or last names).  For a person: [e-mail].

Object-Oriented Systems (New)
-----------------------------
EMail: [e-mail]
http://www.cs.ucl.ac.uk/coside/oos/index.html  (new)
    Russel Winder <[e-mail]>

  USA/Canada:
  Journals Promotion Dept., Chapman & Hall, 29 West 35th
  Street, New York, NY 20001-2299, USA.
  Tel: [phone]
  Fax: [phone]
  EMail: [e-mail]

  EC/RoW:
  Journals Promotions Dept., Chapman & Hall, 2-6 Boundary Row, London
  SE1 8HN, UK.
  Tel: [phone]
  Fax: [phone]

SIGS Publications (9/yr)
------------------------
These publications have staff writers from among the most popular OO authors
and methodologists.
  Object Magazine        - Manager's Guide to Object Technology        $39
  Journal of Object-Oriented Programming - For Progs/Devls using OO    $59
  C++ Report             - Get most out of C++                         $69
  The Smalltalk Report   - How-To Advice for Smalltalk Users           $79
  Report on Object Analysis and Design - Lang Ind/Arch on OOA/D/Mdling $99

  SIGS Publications, Inc.
  P.O. Box 2027
  Langhorne, PA 19047
  Fax:   [phone]
  Phone: [phone]