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Re: Microsoft extensions to XSL (was RE: how to call Javasc

Subject: Re: Microsoft extensions to XSL (was RE: how to call Javascript function in .xsl file) function in .xsl file)
From: Ray Cromwell <ray@xxxxxxxxxxxxxxx>
Date: Wed, 11 Nov 1998 03:09:33 -0500 (EST)
ray cromwell
> By the way tyler, the Javalobby stuff is quite impressive and well done.
> However, most of us has to do more complex sites, like for instance provide
> e-commerce and link to mainframes (yes, these prehistoric beast are still
> alive), link to relational database, etc. XSL is great in a way that it
> provides a good transformation language, javascript is not so efficient for
> that task. But XSL is not able to link to database and build a document from
> data stored in these beast. And if a standard can help us to do that, we
> won't get locked into any religion either called Microsoft or Java. I hoped
> that people from W3 beyond all religions heard this request from people
> having to _deliver_ stuff.

First, it seems to me that if you have to link with legacy mainframes,
DCOM certainly isn't the way to do it. What do you think is more
likely to exist on mainframes and minicomputers -- a CORBA
implementation or a DCOM implementation? I'd expect CORBA from IBM,
not DCOM.  COM has its uses as a component model, much like JavaBeans,
but when all you want is distributed interfaces, I'd say that on
legacy systems, CORBA is alot more mature and available. 


Secondly, I think doing database queries inside the XSL processor is just 
WRONG.  It totally breaks the architectural design IMHO. XSL should
not be in the business of querying a database and building a document.

To me, in the model-view pattern, XML is the data model, and CSS/XSL
are the "view" Any RDBMS/OODBMS/LDAP/IMAP/SearchEngine/whatever
queries should be done and already inserted into the XML before
XSL even sees it. 

If XSL has to perform any dbms queries, it should only be used to change
the look-and-feel (personalization), not the data. An example
architecture is

+------+
|OODBMS|------\                           optional query
+------+       \                           to personalize view
                \                               |
+-----+          \ +-----------+           +-------+ 
|RDBMS| -----------|XML results|---------->|CSS/XSL|---> HTML/PDF/Whatever 
+-----+           /+-----------+           +-------+
                 /
+------+        / 
|Custom|--------
+------+


People who want to use XSL to build documents from databases directly
are too hooked into the ASP/ColdFusion template mindset where one
defines an an incomplete HTML document and fills in the holes via a DB
query in VBScript or ColdFusion tags.

The problem with using XSL for this approach is that at no time is
there ever a complete valid XML document. If you simply invent your
own static tags in XML and have all dynamic data "filled in" at the
XSL level, than a user can never get his hands on an XML document
containing the untarnished data.  What's the point?  If you use XSL
like this, what does it buy you that PHP, JSP, ASP, LiveWire,
ColdFusion don't? You aren't putting any data in the XML, just using
XML tags like neat little macros that expand into HTML chunks.

My own preference is for a simple RDBMS-to-XML mapping language that
takes queries and spits out fragments of XML which can be Xlink-ed
into another document. You author your XML documents normally, but
when you need to include dynamic data, you XLink it in. Performance
may suffer, but caching solves the problem.

This approach works very well for the 90% of common website functions
like providing news bulletins (ala miniportals/aggregrators),
doing a catalog, or a portal-tree, or even providing web chat forums.
The advantage is, the XML documents can be retrieved by the client,
indexed, transformed, etc.

All IMHO,
-Ray



















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