NetNews Usenet Archive 1992 #16/NN_1992_16.iso/spool/comp/parallel/1760

Text File | 1992-07-21 | 26.3 KB | 659 lines

Newsgroups: comp.parallel
Path: sparky!uunet!europa.asd.contel.com!darwin.sura.net!gatech!hubcap!fpst
From: [e-mail] (Feibing Zhan)
Subject: Summary of Responses on Concurrent Object-Oriented Programming
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Date: Fri, 17 Jul 1992 14:40:45 GMT
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The following are the responses I have received so far on my request on
Concurrent Object-Oriented Programming Tools. I simply list them one by one,
and post them here. Each mail is seperated by a row of *'s. I'd like to thank
those who responded my request.

Feibing Zhan
[e-mail]

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

     N E T C L A S S E S   E A R L Y   D E V E L O P E R ' S   R E L E A S E

                  A N D   B E T A   T E S T   P R O G R A M

                  PostModern Computing Technologies, Inc.
                       1032 Elwell Court, Suite 240
                       Palo Alto, California 94303
                        Telephone: [phone]
                        Facsimile: [phone]

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

        In June, 1992, PostModern Computing is planning to distribute
        an early release of its NetClasses product, a set of C++ class
        libraries for distributed object-oriented communications that
        is currently scheduled for production release in the 3rd
        quarter of 1992.

        Some simple example C++ application code written to the
        NetClasses libraries is included in this announcement.

        NetClasses is a set of C++ class libraries that is organized
        as a software toolkit.  The typical user of the NetClasses
        libraries will be a distributed systems application developer
        who requires an object-oriented framework for distributed,
        message-passing based programming.  By linking the appropriate
        NetClasses libraries, application programmers are then able
        to:

         1.  Transport objects over a network.  Currently, there are
             three object varieties that NetClasses can transport:
             1) Arbitrary C++ objects---once derived from PostModern's
             TransObject class; 2) arbitrary NIH-derived objects; and
             3) NetClasses Typed Objects.  NetClasses Typed Objects
             provide an object-oriented data transport in which the
             structure and organization of network transportable
             objects is specified externally in configurable files
             using a simple, programming language independent abstract
             syntax notation, the NetClasses Abstract Syntax Notation
             (NASN).

         2.  Perform remote method invocations (RMI).  Using RMI, an
             application on machine B can invoke a method on machine A.
             RMI insulates distributed applications from the complexity
             inherent in traditional, RPC-based distributed systems
             development tools such as protocol compilers, direct TCP/IP
             code writing, and detailed socket handling.  RMI makes fault
             tolerance and connection management transparent to the
             application programmer.  The RMI layer is built on top of the
             distributed services package that is described below.

         3.  Use the NetClasses application programmer interface in
             order to create, manipulate, and destroy typed objects
             given NetClasses Typed Object data type definitions.
             (NIH-derived and native C++ objects are created, manipulated
             and destroyed from C++ itself).

         4.  Read and write all three varieties of NetClasses-transportable
             objects on streams using machine-independent external
             representations.  All three varieties of objects can be stored
             to and read from files.

         5.  Derive new distributed systems applications and reconfigure
             existing ones by leveraging the multiple inheritance, subtyping
             and data encapsulation capabilities of the NetClasses package.



---------------------------------------------------------------------------
                   Three varieties of object transport
---------------------------------------------------------------------------

        PostModern Computing's NetClasses package provides a set of
        flexible C++ tools for object transport.

        The NetClasses NIH-based and Typed Object-based transports are
        built on top of the National Institutes Health (NIH) class
        library.  However, the NetClasses Typed Object application
        programmer interface is not NIH-dependent.  In particular, the
        Typed Object interface does not in any way constrain C++
        developers who prefer not to use the NIH library themselves.

        The TransObject transport offers C++ programmers a third
        facility for object transport that is entirely NIH independent
        (NIH is not even included in the associated support
        libraries).  The TransObject class library offers end-user
        application programmers a way to migrate existing C++ class
        definitions to a network-transportable framework.  The
        TransObject facility is independent of both the NetClassses
        Typed Object transport and the NIH-based object transport
        described above.

        Here is the actual code to send an object "obj" on port 4001 to
        a client that has requests a connection on that port.  Here, obj
        can be pointer to an object that is either derived from a generic
        C++ TransObject, an NIH-derived object, or a NetClasses TypedObject.


        TCPstrm stream;
        stream.listen(4001);                 // Listen for connections
        TCPstrm* clientStream = stream.acceptConnection();
        clientStream->send(*obj);
        cout << "Sent the following Object\n" << *obj << endl;


        Here is the code for the client:


        TCPstrm stream;
        stream.connect("serv", 4001);       // Connect to serv on port 4001
        obj = stream.receive();             // Receive object
        cout << "Received the following Object\n" << *obj << endl;


        Note that in addition to being sent over a stream, obj is
        written out to cout.  It is also possible to store obj in a
        file for later retrieval.

        Although this example shows how NetClasses shields the developer
        from tedious communications code, it is still a fairly low-level
        implementation in that port numbers and host names must be
        specified.  The developer can be shielded from these details as
        well by using the distributed services and remote method invocation
        facilities described below.

^L
---------------------------------------------------------------------------
                     Distributed Services Paradigm
---------------------------------------------------------------------------

        PostModern Computing's Distributed Service Paradigm is a
        connection and service management mechanism that is organized
        around the idea that network service providers should not have
        to set up explicit port numbers and RPC connections but rather
        should simply ``advertise'' themselves on the network.
        ``Agents'' are active processes on the network that monitor
        network service advertisements and manage connections between
        information producers and consumers.  The Distributed Service
        package is organized as a combination of C++ class libraries
        and configurable "dsagent" executables.

---------------------------------------------------------------------------
                    Remote Method Invocation (RMI)
---------------------------------------------------------------------------

        The distributed services paradigm enables methods to be
        invoked on objects from remote machines.  The RMI facility is
        a higher level communications facility that shields the
        developer from port number and host name considerations.
        The focus of RMI is on ease of use.  An RMI invocation
        requires no stub or skeleton files, protocol compilers, or RPC
        mechanisms.  To enable object X of class C to have its method
        M invoked from a remote machine, a programmer uses
        RMI::advertise method that takes the following form:

                 RMI::advertise("X.M", new RMIMethod(C)(X, &C::M));

        If an application wants to invoke the M method on object X
        from a remote machine, it does

                 RMI::invoke("X.M");

        Parameter passing in RMI can be based on any of the three
        NetClasses object transports (generic C++, NIH-object, or
        TypedObject).  Synchronous and asynchronous RMI versions exist.

        Multiple agents can advertise method X.M.  The one that is
        actually invoked is transparent to the client.  RMI thus
        provides an easy mechanism for developing scalable distributed
        applications.


^L
---------------------------------------------------------------------------
              Detailed description of Typed Object transport
---------------------------------------------------------------------------

        Of the three object transports enabled by the NetClasses
        libraries, the NetClasses Typed Object-based transport will be
        the most unfamiliar to the NetClasses newcomer.

        The NetClasses Typed Object library enables application
        programs to communicate via "typed objects", a machine-
        independent data representation format.  Each typed object has
        associated with it a particular "type", which is in turn
        specified as a collection of "properties".  Both types and
        typed objects are organized in an inheritance hierarchy that
        reflects the object- oriented programming concepts of
        information hiding, and single and multiple inheritance.

        A NetClasses type definition is described in terms of the
        machine- and programming-language independent "NetClasses
        Abstract Syntax Notation", or NASN.  The main goal of NASN is
        to place a level of indirection between how a particular
        application program (written in a particular programming
        language, and running on a particular machine architecture)
        represents and manipulates a typed object, and how the
        corresponding data fields inside a typed object are brought
        into a format suitable for transport over a computer network.
        In its current implementation, NetClasses offers developers a
        C++ application programmer interface for the creation,
        destruction, manipulation, and transmission of typed objects.

        The notion of a "type" is central to Typed Object-based
        application programs.  NetClasses types are similar to types
        in the programming language world.  The main differences are
        that NetClasses types are programming language independent,
        and they are used not only inside a particular program, but
        more importantly as a high-level data communications format
        between different programs.


^L


        Figure 1, below illustrates an example NetClasses type
        definition file.  The type definitions are written in the
        NetClasses Abstract Syntax Notation, or NASN.

                create type Person
                    (name      StringType,
                     address   StringType,
                     phone     CharType 10);

                create type Topic
                    (code         FloatType,
                     nameOfTopic  StringType);

                create type Author subtype of Person
                    (expertise    Topic);

                create type Editor subtype of Person
                    (expertise  Topic  many,
                     codeNumber IntegerType);

                create type Document
                    (title      StringType,
                     authorOf   Author,
                     subject    Topic,
                     editor     Editor);

        Figure 1.  A NetClasses Type definitions file written in
                   the NetClasses Abstract Syntax Notation (NASN).

^L
---------------------------------------------------------------------------
          Example: Typed Object transport using NetClasses
---------------------------------------------------------------------------

        In this section, we show how to use the C++ interface to the
        NetClasses package to write an elementary ``producer and
        consumer'' distributed application which we shall call
        StockQuotation.

        The StockQuotation application involves two programs.  The
        first program, called SQ-Producer, generates a simple stock
        quotation object.  SQ-Consumer is a second program that
        receives the stock quotation object from the first program
        over a TCP stream connection.

        The first step in writing the StockQuotation application is to
        decide upon a NetClasses type definition for the stock
        quotation object that is going to be passed from the producer
        to the consumer:


                 create type StockQuotation
                   (stocksymbol   StringType,
                    price         FloatType,
                    code          IntegerType);


           The file SQ.nasn, defining a Stock Quotation type.


        Next, we show the SQ-Producer program and the SQ-Consumer
        program.  For clarity and simplicity, we have removed all
        run-time error checking from the two programs.
^L
 -------------------------Start of file SQ-Producer.C------------------------

// Start the Producer first, then the Consumer.
// This program expects input from SQ.nasn.

#include <libc.h>
#include <string.h>
#include <iostream.h>
#include "NetClasses.h"
#include "tcpstrm.h"

main()
{
   Type::readTypes();

   Type*        SQType   = (Type *) Type::getType("StockQuotation");
   TypedObject* SQObject = SQType->createObject();

   SQObject->setPropValue( "IBM", "stocksymbol");
   SQObject->setPropValue(110.25, "price");
   SQObject->setPropValue(   321, "code");

   TCPstrm stream;
   stream.blocking(YES);
   stream.listen(4001);

   TCPstrm* clientStream = stream.acceptConnection();

   cout << "Sending the following Object\n" << *SQObject << endl;
   clientStream->send(*SQObject);

   clientStream->close();
   stream.close();
}
-------------------------End of file SQ-Producer.C--------------------------

-------------------------Start of file SQ-Consumer.C--------------------------

//   Start the Producer first, then the Consumer.
//   This program expects input from SQ.nasn.

#include <iostream.h>
#include "NetClasses.h"
#include "tcpstrm.h"

main()
{
        Type::readTypes();

        TCPstrm stream;
        stream.blocking(YES);
        stream.connect("pablo", 4001);

        TypedObject* object = stream.receive();

        cout << "Received the following Object\n" << *object << endl;
}

-------------------------End of file SQ-Consumer.C--------------------------
^L

        After compiling and linking these two programs, we could execute them
        by first typing

            pablo> SQ-Producer < SQ.nasn &

        on the hypothetical machine called ``pablo,'' and then typing

           sundev> SQ-Consumer < SQ.nasn

        on some other machine, here ``sundev.''  On the machine
        ``pablo'' should appear output similar to the following:

         pablo>
         Created type StockQuotation
         Sending the following Object
         TYPE: StockQuotation
         PROPERTY: stocksymbol, TYPE: StringType, VALUE: 'IBM'
         PROPERTY: price, TYPE: FloatType, VALUE: 110.25
         PROPERTY: code, TYPE: IntegerType, VALUE: 321
         pablo>

        The machine ``sundev'' would then output information that
        looks like this:

         sundev>
         Created type StockQuotation
         Received the following Object
         TYPE: StockQuotation
         PROPERTY: stocksymbol, TYPE: StringType, VALUE: 'IBM'
         PROPERTY: price, TYPE: FloatType, VALUE: 110.25
         PROPERTY: code, TYPE: IntegerType, VALUE: 321
         sundev>

^L
---------------------------------------------------------------------------
             A Selection of NetClasses `TypedObject' features
---------------------------------------------------------------------------

        1)  Overloaded == for value-based object equality testing.

            For example we can write:

                  if (object1 == object2) ...

        2)  Object aggregation in `composite' properties.

            Composite properties, which are specified in NASN by the
            keyword `many,' are used to associate multiple instances
            of similarly-typed TypedObjects with one property of a
            (containing) object.  For example the NASN definition

                  create type Library
                     (name     StringType,
                      address  StringType,
                      holdings Book many);

            defines `holdings' to be a composite property of Library.
            Instantiated Library typed objects could then contain multiple
            `Book' typed objects.  Composite properties properties have
            object array semantics.

        3)  Path-notation accelerators for nested object manipulation.

            For example we can write

            employeeObj->setPropValue("Ed Jones","dept.supervisor[3].name");

            to set the name of the third supervisor in this employeeObj's
            dept property to "Ed Jones."

        4)  Machine-independent external data representation.

        5)  Exposed Type, Property and TypedObject methods.

            Implementation hooks allow programmers to substitute alternative
            parsers and user-interfaces for the NetClasses abstract syntax
            notation.  (This is partially intended as an OMG migration
            path).
^L
MISCELLANEOUS INFORMATION:

---------------------------------------------------------------------------
                         Transport mechanisms
---------------------------------------------------------------------------

        In the first developer's release, NetClasses includes TCP- and
        UDP-based object transport mechanisms.  PostModern's Reliable
        Broadcast Protocol (now under alpha testing) is a UDP-based
        layer for _reliable_ object transport in nonconnection-oriented
        environments.  The TCP, UDP, and Reliable Broadcast Protocol
        facilities are all organized as C++ class libraries.

----------------------------------------------------------------------------
                NetClasses frequently asked questions list
----------------------------------------------------------------------------

        1)  How is the beta release organized?

            The NetClasses beta test release is organized as three
            subdirectories.  Each subdirectory enables a different
            variety of object transport, as follows:

            netclasses/generic:

              Contains class libraries and support documentation
              for writing applications that move generic C++ objects
              over a network on top of TCP/IP.  Contains in particular
              the TransObject class, from which users derive existing
              classes in order to enable TCP/IP-based object transport.
              Includes streams, distributed services and Remote Method
              Invocation support libraries.

            netclasses/nih:

              Contains class libraries and support documentation
              for writing applications that move arbitrary NIH-derived
              objects over a network using TCP/IP.   Includes streams,
              distributed services and Remote Method Invocation support
              libraries.

            netclasses/types:

              Contains class libraries and support documentation
              for writing distributed applications that move
              PostModern Computing's Typed Objects on top of TCP/IP.
              Users will first create NetClasses Typed Object data
              definitions in external files using the NetClasses
              Abstract Syntax Notation (NASN). The Types package C++
              API is then used in order to create, manipulate, transmit,
              and destroy objects that meet these definitions.  Includes
              streams, distributed services, and Remote Method Invocation
              support libraries.

            By using the appropriate object transport and support
            libraries, users can move objects over TCP/IP stream
            connections.  Simple code examples are included in each
            subdirectory, and they are explained in the associated
            support documentation.  The RMI library allows application
            programmers a further level of abstraction in that host
            name, port number, and connection management duties are
            taken over by active processes that are called distributed
            service agents (dsagent).  An application wishing to send
            objects over the network "advertises" itself to an agent as
            a service provider, while processes wishing to receive
            objects request connections to these services through
            these agents.

        2)  Is the beta release _really_ going to include all this software?

            Yes.  The only things that could possibly slip are the Remote
            Method Invocation libraries.  The distributed services package
            that RMI is built on top of will certainly ship in the beta
            release.

        3)  What information do I need to provide?

            We need your mailing address, the system you are using
            (e.g. SUN OS 4.1.2), and the media you would prefer (our
            default is to ship on 1/4'' cartridge tapes in QIC-150
            format).  We are using Sun C++ compilers.

            Along with the tape, you will receive a nondisclosure
            agreement that you should sign.

        4)  What platforms does NetClasses run on?

            We are currently testing on Sun Sparcstations and HP workstations.

        5)  When will this software be available?

            We plan to ship copies to beta test sites in mid- to late-June.

        6)  Has retail pricing been decided upon?

            No.

        7)  Will my input to the beta testing program matter?

            Yes, and probably a lot.  We want this product to be
            simple, modular, and useful.  Most of the interest we have
            received is coming from research laboratories and
            companies that are facing similar problems to what we are
            trying to solve with these libraries.

        8)  What is the structure of the beta test program?

            We will send you the libraries, headers, and draft
            documentation.  You tell us bugs and things you find
            useful or inconvenient.  Sending a message to
            [e-mail] is probably the best way to be
            heard.

        9)  Do I have to pay anything?

            Nothing except the shipping and media costs.  (If we were to pay
            for the shipping we would have to limit the number of beta copies
            we ship, and we don't want to do that).


                  PostModern Computing Technologies, Inc.
                       1032 Elwell Court, Suite 240
                       Palo Alto, California 94303
                        Telephone: [phone]
                        Facsimile: [phone]


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

You may like to contact

----------------------------------------------------------------------------
Mjolner Informatics Aps                            Phone: [phone]
Science Park Aarhus                                Fax:   [phone]
Gustav Wiedsvej 10                                 Email:
[e-mail]
DK-8000 Aarhus C, Denmark
----------------------------------------------------------------------------

as they have:

The Mjolner BETA System



         A software development environment supporting
                  object-oriented programming
               in the BETA programming language

I have not had a chance to experience with it, but it sounds interesting.


**************************************************************************
Mentat is a medium-grain dataflow CSP implementation of C++.  It may be
found at the University of Virginia and has been implemented on Suns
and an NCube (I think.)  It's shareware.

Contact asst. prof. Andrew Grimshaw at [e-mail] (or is it
cs.uva.edu?)  It's his baby.



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

You can get an extension of C++ with parallel features (called uC++)
via anonymous ftp (number: 129.97.129.9). Sorry, but I don't know the
exact directory (I think pub/...). There is a file u++-3.2.5.tar.Z.

If you get other answers please can you forward it to me.

Thank you

   Dietrich.


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

Two Concurrent OOPL's that are available in the public domain are:

 - Modula-3 from DEC SRC; ftp from gatekeeper.dec.com
   /pub/DEC/Modula-3/m3-??.tar.Z

 - uC++ from University of Waterloo; ftp from watmsg.uwaterloo.ca
   (129.97.141.9) pub/dmake/dmake38.tar.Z

Hope this is to some help.


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

Not public domain, but I thought I'd drop you a line just in case you
were interested in the information.

There is a whole programming tool environment which is far more
object-orientated than the likes of Express, and PVM etc. called
TOPSYS produced at the University of Munich (TUM - Technische
Universitat Munchen, with a few accents here and there!!!).

A few contact names if you are interested:
Thomas Bemmerl
Christian Kasperbauer
Martin Mairandres
Bernhard Ries.

At least those are the names on one of the more major reports I have
on that work!!

I have an up to date Email address for Thomas Bemmerl which I found
easily, I don't know whether I have information on the others.
Thomas' address is [e-mail], as he is now with Intel
ESDC.

Hope this was helpful,