Re: some information about anchor modeling
Date: Wed, 31 Oct 2012 22:01:53 -0700 (PDT)
On Wednesday, October 31, 2012 2:19:19 AM UTC-7, vldm10 wrote:
> On page 211, Appendix A / Primary Keys Are Nice but Not Essential,
> of his last book, "Database Design & Relational Theory – Normal Forms & All That Jazz” C.J. Date writes about “anchor relvars”
He is just using it in its everyday metaphoric sense of a rooted base. Google gives a Safari book preview of a few lines, below. (I have the book, this enough to give you an idea of his usage, introduced here.) See http://en.wikipedia.org/wiki/Relational_Model/Tasmania re kernel entities of RM/T.
- Primary Keys Are Nice but Not Essential ONE PRIMARY KEY PER ENTITY TYPE? I turn now to the second of the two issues mentioned in the introduction to this appendix: viz., that entities of a given type are supposed to be identified in exactly the same way everywhere in the database. What this means, loosely speaking, is that there’ll typically be: A single “anchor” relvar for the pertinent entity type, having some particular primary key, together with Zero or more subsidiary relvars giving further information about entities of that type, each having a foreign key that refers back to the primary key of that anchor relvar. (Does this state of affairs remind you of the RM/T discipline discussed in Chapter 15?)
he Received on Thu Nov 01 2012 - 06:01:53 CET