Re: object algebra

> This seems obvious ...
> Finding all possible combinations of 2 children is ludicrously simple.

Without actually presenting a solution, the possibility remains that your conclusions maybe off (and by a substantial margin).

We both agree that NULLs are not part of relational algebra. Codd correctly realizes that NULLs are an integral part of RDM since it creates them when representing some things due to the "rectangularish" shape of relations, unless one resorts to generic modelling which in the extreme case results in a one-columned table and is not a practical solution. You contend that NULLs are not part of RDM. Therefore, I want you (or anyone else) to show me how RDM replicates the simpler example shown at www.xdb1.com/Example/Ex076.asp

"This example represents things in a command hierarchy and generates a report indicating the closest common commander between all possible pairs. For example, john and mary obey the army. Army is their closest common commander. The first figure shows the various types of things and their instances. The second figure shows the command hierarchy starting with god."

1. Represent the equivalent things and hierarchy without NULLs. Note: each person has different properties. Note: the hierarchy consists of different types of things. Note: things in the hierarchy may have 1 to many commanders.
2. Generate the equivalent common ancestor report.

Only by actually working thru the solution will you see how the "rectangularish" shape of relations offers a less generic solution than TDM/XDb1.

And if the report generates under 15 ms from normalized data, that would be nice. Received on Wed Feb 25 2004 - 04:50:12 CET