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<DIV><SPAN class=669434807-07052002><FONT face=Arial color=#0000ff
size=2>Pascal,</FONT></SPAN></DIV>
<DIV><SPAN class=669434807-07052002><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=669434807-07052002><FONT face=Arial color=#0000ff size=2>The
main intent with this is to support the schema developers.</FONT></SPAN></DIV>
<DIV><SPAN class=669434807-07052002><FONT face=Arial color=#0000ff size=2>It
would be nice to think that all EXPRESS parsers supported the latest version, in
that case I guess we could do away with this mechanism. However, life is not
like this!</FONT></SPAN></DIV>
<DIV><SPAN class=669434807-07052002><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=669434807-07052002><FONT face=Arial color=#0000ff size=2>As the
author of a schema you decide what you want to capture in your model, and which
constructs of EXPRESS you are going to use. As a result you control which
version of EXPRESS you are using. To assist people working with you, or using
your model it is, our belief, useful to inform them formally which version of
EXPRESS you have used. If you do not then it is highly likely that you will
receive complaints that your model is wrong since others will undoubtedly use
different tools to verify the model that you have used.</FONT></SPAN></DIV>
<DIV><SPAN class=669434807-07052002><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=669434807-07052002><FONT face=Arial color=#0000ff size=2>I know
this happens through personal experience. I was writing a model for a customer,
and one of the constraints required TC2 level support. The EXPRESS toolkit they
was using rejected the constraint and refused to build the required data
structures. As a result the customer, knowing that I knew EXPRESS pretty well,
asked me to contact the support desk of their EXPRESS toolkit vendor. On
doing this I was told that this was the expected behaviour, and that the
construct I had used was wrong. Further more could they help by providing
EXPRESS training to me, since I was obviously in need of it!</FONT></SPAN></DIV>
<DIV><SPAN class=669434807-07052002><FONT face=Arial color=#0000ff size=2>I was
able to sort things out fairly quickly by calling the person from the vendor
company who attends ISO meetings, and the parser was
changed.</FONT></SPAN></DIV>
<DIV><SPAN class=669434807-07052002><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=669434807-07052002><FONT face=Arial color=#0000ff size=2>For
many people they need the confidence in the tool that is does support the
EXPRESS they have written, although this is not guaranteed by this approach, it
should allow tools which do not support the latest version to be easily
identified.</FONT></SPAN></DIV>
<DIV><SPAN class=669434807-07052002><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=669434807-07052002><FONT face=Arial color=#0000ff
size=2>Phil</FONT></SPAN></DIV>
<DIV><SPAN class=669434807-07052002><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<BLOCKQUOTE dir=ltr
style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #0000ff 2px solid; MARGIN-RIGHT: 0px">
<DIV class=OutlookMessageHeader><FONT face="Times New Roman"
size=2>-----Original Message-----<BR><B>From:</B> Pascal Huau
[mailto:pascalhuau@goset.asso.fr]<BR><B>Sent:</B> Monday, May 06, 2002 10:04
AM<BR><B>To:</B> Phil.Spiby@eurostep.com<BR><B>Cc:</B> WG11<BR><B>Subject:</B>
Re: Identification of Express Version<BR><BR></FONT></DIV>
<DIV><FONT face=Arial size=2>Dear all,</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>I would like to add my two cents (of Euro) in the
debate.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Q1: Is it needed to indicate the version of the
Express language in an Express schema?</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>
<DIV><FONT face=Arial size=2>If I am the customer of an application, the
answer to Q1 is no. (If I am expert enough to know that there are several
versions and TCs of Express) I want to know which version and TC of
Express, the application implements and the marking of Express schemas does
not provide me any information about that.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>If I am developer of an
Express application, the answer is also no.</FONT></DIV>
<DIV><FONT face=Arial size=2>Either my application implements the latest
version of the language or it does not. </FONT></DIV>
<DIV><FONT face=Arial size=2>If it does not, then it will return an
error when it encounters an Express language construct (e.g. extensible
select) that did not exist in the version of the language that was considered
at design of my application.</FONT></DIV>
<DIV><FONT face=Arial size=2>If it does, then the application will hopefully
recognize all language constructs. As long as upward compatibility is kept in
the specifications of Express language, these constructs can be interpreted
correctly by the application, whatever they are old or new constructs.
</FONT></DIV>
<DIV><FONT face=Arial size=2>So the actual question to answer is:
</FONT></DIV>
<DIV><FONT face=Arial size=2>Q2: is Express2 upward compatible with
respect to Express1? Are all the Express1 constructs still valid in Express2?
Is there any restriction in their specification that has been introduced in
Express2?</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Regards,</FONT></DIV>
<DIV>Pascal Huau<BR>Association GOSET<BR>107,111 avenue Clemenceau<BR>92000
Nanterre<BR>France</DIV></BLOCKQUOTE></BODY></HTML>