Re: object algebra

> > > XDb1 has "amaterish" transitive closure
> > Why not show how amaterish it is by providing an alternate solution?
> but finding nearest common ancestor in a tree is trivial:

I can't tell by the provided 4 steps, if the alternate solution is more or less "amaterish".

> I'm not sure what exactly your challenge is:

1. Model the data shown at www.xdb1.com/Example/Ex076.asp The data is described quite accurately by sentences like "john isa person". The two figures show views of the final data as trees. There isn't much table-like data, so nothing was displayed in the grid. 1a) You don't have to model the relator "obeys" 1b) All tables must be NULL-less (XDb1's data is NULL-less). 1c) Data must be normalized (Don't normalize down to atomic symbols as XDb1 does, but normalize things like john, mary, fido, etc).
2. Create a "Nearest Common Ancestor Report" for things in the command hierarchy. I have copied the report below from the webpage. The order of things can be different.

Common Ancestor Report for 'god'

ThingX	ThingY	CmnAnc	Dist
army	john	army	1
army	laptop1	army	2
army	fido	army	2
army	mary	army	1
army	trinity	god	2
army	luke	god	3
john	laptop1	john	1
john	fido	john	1
john	mary	army	2
john	trinity	god	3
john	luke	god	4
laptop1	fido	john	2
laptop1	mary	mary	1
laptop1	trinity	trinity	2
laptop1	luke	trinity	3
fido	mary	mary	1
fido	trinity	trinity	2
fido	luke	luke	1
mary	trinity	trinity	1
mary	luke	trinity	2
trinity	luke	trinity	1

XDb1's representation/gui/code is generic enough so that someone else could enter a completely different hierarchy consisting of different things and yet the report would run properly. Your code/SQL should have a similar level of genericness. Received on Fri Feb 27 2004 - 04:14:52 CET