Looks like you're referring to the category REL (category of relations). I wonder if the category theory has any interesting insights that are not already covered by relational algebra used to argue about relational databases. Even if it doesn't have, it's intersting to see how relations are described using the language of the category theory.

I just learned about REL yesterday, reading Slide 1.20 of

http://www.cs.nott.ac.uk/~gmh/cat1.pdf

http://en.wikipedia.org/wiki/Category_of_relations

http://nlab.mathforge.org/nlab/show/Rel

Regarding "Using the concepts of Category Theory to create better XML data models",

on Friday, August 03, 2012 22:40:52,

Costello, Roger L. wrote to xml-dev@l... <xml-dev@l...>

> I am learning Category Theory [1] to enhance my data modeling skills and my

> functional programming skills.

>

> Despite just starting to learn the subject, I have already discovered some

> exciting things that I will be able to use in XML data modeling and in XSLT

> functional programming.

>

> Here's what I've learned:

>

> http://www.xfront.com/Using-the-Concepts-of-Category-Theory-to-Create-Better

> -XML-Data-Models.docx

--

Nicholas Sushkin <http://www.openfinance.com>