Not quite on topic, but it does follow a thread from last week.

Why did Object-oriented database systems never catch on? This is
SAP's take on it, but makes sense:

http://www.sapdb.org/pdf/backsapdb_eng.pdf

The argument is that the app server middle tier became the thing that
handles the complexity, eliminating the need for overly feature-
burdoned OODBMS.

Regards,
Andrew Ferguson
-- Nine of out ten computers prefer Andrew.