What do we mean by GUID?

Peter Dawyndt Peter.Dawyndt at UGENT.BE
Wed Oct 12 18:26:59 CEST 2005

Dear Matt,

> There are some tricky issues
> dealing with granularity of the identifier for digital data (does the
> identifier point at a tuple in an entity, or at a whole entity, or at
> multiple entities).  In addition you still have the very thorny issue of
> what is data and what is metadata.  I'll write another note regarding
> this issue.

the Object Model formulated by the Object Data Management Group (ODMG;
/www.odmg.org) which is the "de facto" standard for object oriented design
has formalized this issue with the separation between literals (entities
carrying no identifier) and first class objects (entities carrying
identity). A first class object is composed of other first class objects
or literals, while literals themselves are atomic. How this granularity
should be used for a particular application is completely
application-dependent, eg. if a certain application requires that the
instances of a given object (that were considered as literals before)
should be individually identified, then they must be regarded as first
class objects on their own. It is worth to delve into this formal
standard, before making attempts to reinvent the wheel.

Kind regards,


Further reading:

Catell R. & Barry D. (1997). The Object Database Stanard: ODMG 2.0. Morgan
Kaufmann Publishers

More information about the tdwg-tag mailing list