Richard Gambrell wrote:

>Ok, so far as my understanding goes (and I could be quite wrong) XML is
>EDI reborn with what looks like a simpler structure.  Like EDI, what or
>who will create standards for exchange of data?  Is there reason to think
>the XML effort will go any further than EDI?

In a previous life, I worked for Trinary Systems, a company who has EDI
software for Unix, NT and MPE/iX.  Our friends at MB Foster really manage
the product for MPE/iX.  I discovered XML from the EDI point of view but its
roots are really in SGML.  The whole EDI thing deserves its own thread or a
private post.  In brief, I think folks are trying to avoid the cost of a
translator (which are expensive for smaller companies) but I don't see
enough progress in application integration - the real meat of EDI.

>...My problem is does XML increase the complexity of what needs
>to be done beyond the benefit (like EDI for "casual" use seems to)?

For a single purpose, maybe so.  But if you want to enable to integrate with
other XML aware systems then no.

>XML DTD looks to me a lot like database schemes.  I imagine Allegro's
>DBHTML generator could be turned into an DBXML-DTD generator with ease,
>but can one take the data in a well structured Image database and generate
>a useful DTD for the data in the database?

Important point.  DTD's only determine which tags must/may appear and in
what order.  They do *not* describe the data like a database schema.  So how
is this done in XML?  YAXS (Yet Another XML Standard) XSchema!  Microsoft is
big in this area and expect more W3C recommendations this year.

>SGML may be great for publishing as we know it and even hyperlinked web
>pages as we know it, but it hasn't taken the database world by storm
>(maybe it should?). Doesn't a database separate content from
>presentation?  But relational and network databases can express
>relationships more complex than XML hierarchical approach appears to me to
>support.

The way Oracle and IBM look at XML data is they just view it as a note
field.  Should XML replace databases?  IMHO - NO WAY.  Should we be able to
store XML documents in a database.  Why Not?  DB2 and Oracle even have
keyword indexing (like Omnidex/Superdex) on the XML documents they store (or
so I have read).

>[snip]
>Do I use a different DTD for each of the student and the faculty, which
>are highly similar yet have different other attributes, and yet another
>for the building and room perspective and another for the pure event
>perspective, and yet another for the course (not the instance of a course,
>but the course) itself or can I use one DTD with multiple high level
>objects each repeating some of the other's content?.  I can carefully keep
>the same names for the same things so there are relationships *implied*,
>but how can these be expressed explicitly?

First, every XML document doesn't not need a DTD.  It must be well-formed as
mentioned in a previous post.  When it comes to databases, I see XML as a
method to transfer result sets.  I just see the XML document as a view.  One
view can be a student's record, another can be the class roster, another can
be a room's schedule, etc.  As you said, hierarchical representations can
not show all data at once.  (Isn't that way we have short-cuts and links in
file systems?)  Also, future XML agents will be able to use XSL to rearrange
documents into different view, but until they become more prevalent, it will
be better to do it on the server.

Mark Wonsil
4M Enterprises, Inc.