Monday, November 28, 2016

This Week


1. What's wrong with this picture?

"Our terminology is broken beyond repair. [Let me] point out some problems with Date's use of terminology, specifically in two cases:
  1. "type" = "domain": I fully understand why one might equate "type" and "domain", but ... in today's programming practice, "type" and "domain" are quite different. The word "type" is largely tied to system-level (or "physical"-level) definitions of data, while a "domain" is thought of as an abstract set of acceptable values.
  2. "class" != "relvar": In simple terms, the word "class" applies to a collection of values allowed by a predicate, regardless of whether such a collection could actually exist. Every set has a corresponding class, although a class may have no corresponding set ... in mathematical logic, a "relation" *is* a "class" (and trivially also a "set"), which contributes to confusion.
In modern programming parlance "class" is generally distinguished from "type" *only* in that "type" refers to "primitive" (system-defined) data definitions while "class" refers to higher-level (user-defined) data definitions. This distinction is almost arbitrary, and in some contexts, "type" and "class" are actually synonymous." --Comment

2. Quote of the Week

"Physical models depend on the storage mechanisms being targeted. For SQL DBMSs, I would focus on tables and the associated integrity mechanisms ... The basic difference between an ER model and a relational model is that an ER model distinguishes value sets from entity sets. Mapping between entity sets gives us relationship sets and mapping from entity or relationship sets to value sets gives us attributes ... Thus, if a physical model is designed to implement a logical model, there are no such things as "entity records", only physical representations of relations which, denormalized for practical reasons, may superficially resemble structured entities."

3. To Laugh or Cry?

4. Online debunkings
See my comment on independence and triggers

5. Of Interest

And now for something completely different

The PostWest (The future of the West is all behind it)

The best thing you can do to really understand the Israeli-Palestinian Conflict, Islam and the Middle East and the Western never-ending utter failure to deal with that is to read Martin Kramer.

Article of the week

Counter-Error: Separating Fact from Fiction in the Middle East

Videos of the week

Pinch-me of the week
Lebanon's new president vows to 'protect' country from ... Israel!

Book of the week (Purchase via this link to support the site)

Note: I will not publish anonymous comments. If you want to say something, stand behind it. Otherwise don't bother, it'll be ignored.

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