RE: XML as an interface

[johns@syscore.com (John F. Schlesinger)]

Stephen,
I think a key question is whether the schema of the messages is known or
whether it will be changing.

If, as I suspect, you will be using a known schema, it is probably better
not to use a general parser at each end of the communication. Rather, it may
be better to use one of the toolkits on the market to generate more specific
objects to handle the XML messages. Look at eXactML
(http://www.bristol.com/exactml/index.html) for instance, which will handle
the C++ client. Also look at the Oracle class generator
(http://otn.oracle.com/tech/xml/classgen/index.htm) which will generate Java
classes for constructing the XML.

In both cases, you supply the schema and the tool generates the C++ or Java
classes. This is faster than DOM or SAX and provides validation but is less
flexible - a change the schema will need a recompile. To get around this I
would recommend using XSL between the client and the legacy system. You can
use two XSL transforms, one from the schema of the sender to canonical form
and then another from canonical form to the schema of the receiver. This
will insulate both ends from external change (loose coupling). You can start
using the same schema at both ends and have 'null' transforms. The first end
to change will need a 'real' transform. Once both ends have changed, you
will be using both transforms.

You can run the transforms at each end or centralize them in a broker. This
is the most flexible architecture. But also the most expensive...

Yours,
John F Schlesinger
SysCore Solutions
212 619 5200 x 219
917 886 5895 Mobile

-----Original Message-----
From: stephen_lake@sts.co.uk [mailto:stephen_lake@sts.co.uk]
Sent: Tuesday, February 13, 2001 5:41 AM
To: xml-dev@lists.xml.org
Subject: XML as an interface


     Good Morning,

     I have a problem!

     I am working on a (legacy) product that needs to have an XML
     interface. Let me give some background.

     The product is written in C++, and sits on a client machine. The
     product launches a JVM. There is an application server (WebLogics),
     and the data access is using EJB's. We are communicating between the
     server and the JVM using JMS. The messaging system will be carrying
     the data as XML.

     My problem is the conversions:
     1, The (java) server needs to be able to create the XML from the data.
     2, The (C++)  client needs to be able to create objects from the XML.

     Could someone point me in the correct direction for these two
     processes.

     Regards


     Stephen  J Lake








***********************************************************************
This message has been sent via the Internet. Internet communications
are not secure against interception or modification. Severn Trent
Systems therefore can not guarantee that this message has not been
modified in transit, and this message should not be viewed as
contractually binding.

This message and any files transmitted with it are confidential and
intended solely for the use of the addressee. If you have received
this message in error please notify the sender and destroy your
copies of the message and any attached files.
***********************************************************************
Severn Trent Systems Ltd : a part of Severn Trent plc.
Registered in England and Wales Registration No. 2394552