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

["Champion, Mike" <Mike.Champion@SoftwareAG-USA.com>]

> -----Original Message-----
> From: Eric van der Vlist [mailto:vdv@dyomedea.com]
> Sent: Saturday, October 20, 2001 3:16 AM
> To: XML Everywhere
> Cc: xml-dev@lists.xml.org
> Subject: Re: [xml-dev] XML Database Decision Tree?

I agree with Eric's point that the RDBMS systems faced the same uphill
battle against the conventional wisdom 10-15 years ago that XML DBMS systems
do today.  

> As you know, at this  point, it took only a couple of years to wipe
hierarchical 
> databases out.

BUT for the record, the hierarchical DBSMS have not exactly been "wiped
out." They lost most of their *mindshare* in the trade press in a couple of
years, but still keep on truckin' in the back offices of almost all large
enterprises.
According to
http://www-4.ibm.com/software/data/ims/highlights/experform.html
"More than ninety-percent of the Fortune 1000 companies use IMS. IMS serves
200 million end users, managing over 15 billion Gigabytes of production data
and processing over 50 billion transactions every day. IMS still owns the
high-volume on-line transaction and database management environment."
Adabas is not precisely a hierarchical DBMS, but is usually lumped in with
IMS. It has 3000 customers, mostly large enterprises; I can't find hard
figures, but I will guess that there's something like 1 or 2 billion
gigabytes of production data managed by Adabas.  

In any event, if either IMS or Adabas suddenly went away (e.g., on 1 January
2000), the world economy would come to a standstill: the banks couldn't send
money around, most big companies couldn't keep track of who owed what to
whom, the credit card system would collapse, the telephone companies
couldn't track who called whom when via which intermediaries, many airlines
couldn't schedule their people and equipment ... and on and on.  RDBMS could
pick up the slack, eventually, and after a massive investment in the
hardware infrastructure  -- ever wonder why the big hardware companies are
such good buddies with the RDBMS vendors?.

Anyway, the RDBMS swiftly displaced the hierarchical DBMS in the collective
mindset because they addressed a new set of needs -- affordable data
processing in smaller organizations, more flexible queries, methodologies
for database design, independence of logical and physical design, etc.  XML
DBMS will not displace RDBMS in the back offices of the world, but they will
gain mindshare because they address a new set of needs: to handle
semi-structured documents efficiently, demands to build new e-business
applications in "internet time", the need to cache and log transactions
performed via XML messages, the need to maintain the state of complex
multi-way transactions involving high-latency, unreliable internet and
wireless  connections (see my comments on XML "tuple spaces"), and so and so
on.