object databases

[Michael.Kay at icl.com]

Paul Prescod:
> You didn't really answer my question. If Oracle 8i provides the same
> support for "graphs of data with links and annotations" that 
> ObjectDesign then in what sense is it NOT an object database. I'm still 
> asking for a definition.

There are a number of definitions of an "object database", but a minimal
definition requires it to be a container of "objects" - which include
behaviour
(interfaces and methods) as well as structure. Plus a type hierarchy, plus
persistent identifiers... Rather more than just graph structures.

The main area where the "pure object" db vendors differ from the "extended 
relational" vendors is in insisting that the concept of object database also
implies persistent programming, i.e. access to persistent objects using the
same
syntax as transient variables. Also they typically have a completely
different
internal architecture which optimises the performance of navigation and
retrieval of
composite objects at the expense of ad-hoc query.

Mike Kay

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