On May 29, 2008, at 6:08 PM, Jan Urbański wrote:
Now about the idea itself:http://www.informatik.uni-augsburg.de/de/lehrstuehle/dbis/db/ publications/all_db_tech-reports/tr-2001-7_kie_koe/ tr-2001-7_kie_koe.pdf That's one of the basic papers about Preference SQL, explaining what it's all about. For those, who don't feel like reading through it just because I said it's interesting, here's some more info (warning, it's a bit formal):Preference SQL is an extension to regular SQL, that allows expressing preferences in SQL queries. Preferences are like "soft" WHERE clauses. A preference doesn't need to be satisfied by a tuple for it to appear in the result set, but it's "preferred" it is. More strictly, a set of preference clauses in a SQL query defines a partial order on the result set as it would appear without any preference clauses and then returns the maximal elements. The partial order imposed by the set of preferences P[1], P [2], ..., P[n] is such that tuple T1 > T2 iff T1 all preferences T2 satisfies and there is a preference satisfied by T1 and not satisfied by T2 (or there is a preference satisfied by T1 that is "better" satisfied by T2 and all others are "equaly" satisfied). As can be seen, there could be an order defined on the degree of satisfyiness of a preference, and the exact semantics are not all that well defined for all concievable cases. Defining a complete semantics will be a part of my thesis.
This seems like a subset of http://pgfoundry.org/projects/qbe/ ... or do I misunderstand?
-- Decibel!, aka Jim C. Nasby, Database Architect [EMAIL PROTECTED] Give your computer some brain candy! www.distributed.net Team #1828
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