Re: [xml-dev] XML Database Decision Tree?

[Dan Weinreb <dlw@exceloncorp.com>]

   Date: Wed, 24 Oct 2001 15:09:57 +0200
   From: Nicolas LEHUEN <nicolas.lehuen@ubicco.com>

   So I believe there is a whole set of problems that will benefit from XML
   databases (which are I believe based on the hierarchical database model*,
   maybe Mike can confirm/infirm). The storage, indexation and querying of a
   set of document-oriented data is a good example. 

		   We could even say that the XML database model is just a come
   back of the hierarchical model that was supposedly "killed" by the
   relational model back in the 80s.

Over the past ten years, I can tell you that whenever anybody calls
something a "database", and its model is not relational, they get
told:

-- Your data model is equivalent to The Hierarchical Data Model
-- The Hierarchial Data Model was utterly refuted and discredited
   by the Relational Data Model
-- Ergo, your database is no good.

All kinds of database systems that called themselves "object-oriented"
or "semantic" have been and are criticised in this way.

The thing is, there isn't any such thing as The Hierarchical Data
Model.  Just look somewhere for a definition of it.  There *is* such
thing as "the way the IMS product represented data".  To imply that
XML and IMS use the same data model is rather far-fetched.

Also, XML's data model isn't really hiearchical, due to the presence
and semantics of ID and IDREF, which are critically important to XML's
expressive power.  A very illustrative example is the ebXML
Collaboration Profile Agreement (CPA).

   But XML databases isn't or (won't) be a revolution, blasting all other
   storage models. 
				     I don't think XML databases are the "next
   thing".

XML absolutely won't "blast" all other storage models or data models,
and if by the "next thing" you mean supplanting relational databases, I
agree completely that they won't.  I don't think anybody on this mailing
list is supporting any such strawman argument.

   Date: Wed, 24 Oct 2001 10:55:22 -0400
   From: "Champion, Mike" <Mike.Champion@SoftwareAG-USA.com>
   Subject: RE: [xml-dev] XML Database Decision Tree?

						    I innocently asked, "So,
   Amazon is doing a 20-way join on a multi-terabyte database everytime I bring
   up a page?  Wow, I didn't know that RDBMS technology had come that far."
   The Boss (who had served time in the Real World) basically replied "MO-RON!
   They probably denormalize it to hell, and pre-build views that represent the
   way people actually look at the data."  [For the record, I have NO IDEA how
   Amazon works so well, I'm just relaying folklore]. 

Funny you should mention Amazon.  You bet they aren't doing any 20-way
joins when you browse a web page.  You will soon be seeing press
releases about how Amazon is using ObjectStore for some important
functions in its web site.  (Sorry, not being in marketing I'm not
sure what we're currently allowed to say, but I know it's coming out
soon.)