relational and object-oriented DBMSs
Dennis Moore of RTI writes:
|Many CAD and CASE applications currently don't use any existing DBMS,
|relational or otherwise. Or if they do, they only use it at a high
|level of granularity, or for peripheral functions. Few or none of
|them use a relational DBMS to store, say, individual transistors, or
|whatever are the small elements in which the program primarily deals.
|Since they're not using a relational DBMS now, there's no issue of
|"staying with an evolving rdb".
This is common disinformation that OODB companies have been spreading in
an attempt to generate a "need" for their product. Most CASE companies
use RELATIONAL databases at the hearts of their products. For instance,
Disinformation!? I work with Dan at Object Design, Inc., where we are
building a C++-based OO DBMS. Dan wrote about "many" CAD and CASE
companies, not "all". Furthermore, his information comes from *many*
hours spent with CAD and CASE tool builders, discussing their
requirements. Finally, before joining Object Design, Dan, myself, and
many of our colleagues, spent several years at jobs where we had the
opportunity to learn about the requirements of many "non-traditional"
DBMS application areas, including CASE, MCAD, ECAD, geographic
information systems, computer-aided publishing, and document
management. Based on all this information, we concluded that there is
a need for high performance for fine-grain manipulation of small,
persistent objects. The OO DBMS companies are not generating a need,
they are building products that respond to a need. We often hear
comments of the form "we needed it yesterday".
Many databases have substantial object-oriented features; many of these
databases are traditional RDBMSs. There is no exclusivity between OO- and
R- DBMSs. For instance, ... [list of features] ...
These features will improve our
usability in several types of applications: data dictionaries
(CASE/CAD/CAM/CAE/etc.), computer integrated manufacturing (CIM), expert
systems, and others.
Yes, and I can run ray-tracing software on an 8088-based PC, but I
don't think that I'd have much luck selling the combination as a hot
The essential operation in many CAD applications, (the ones that Dan
was referring to), is to locate an object given its id. This is a very
fundamental operation, and performance will, to a large extent, depend
on how it is implemented. Because the operation is so basic, it is not
the sort of thing that can be changed once the DBMS has been built. It
is therefore difficult for me to imagine how a relational DBMS can
obtain the performance levels required by the customers being
targetted by the OO DBMS builders.
Object Design, Inc.