[GOODIE] BinaryRelation
Richard A. O'Keefe
ok at cs.otago.ac.nz
Mon Mar 31 21:39:09 UTC 2003
Avi wrote:
Come on, I'm not "bemoaning" anything, nor do I think the "only" is
necessary. As I said, an algebra of binary relations is a natural
approach for what you're doing, but it's rather awkward to model a set of
Oracle tables that way (or at least, it seems so in my ignorance - feel
free to enlighten me).
I want to point out that the purpose of my BinaryRelation class is
*NOT* to model a set of Oracle tables but simply to plug a gap in
the data structures available to *programmers* for in-memory programming.
Over many years I have learned to think of relations as a valuable tool
for my own programming and design *without* any reference to relational
databases as such.
(BinaryRelation now includes #converse, #reachableFromSource[s]:,
#reachableFromTarget[s]:, and #* .)
E. F. Codd has published a list of 12 criteria for what makes something
a relational database. (At the time, SQL did _not_ qualify...) Amongst
other things, persistence, audit/recovery, and authorisation control are
important. These things must be dealt with in any Smalltalk modelling
of Oracle tables. They are completely irrelevant to a set of pairs
data structure for internal programming use.
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