# cdt glossary [Graph] (was: what are keys and surrogates?)

From: mAsterdam <mAsterdam_at_vrijdag.org>

Date: Fri, 11 Jan 2008 09:12:15 +0100

Message-ID: <478723c5$0$85785$e4fe514c_at_news.xs4all.nl>

> is defined as a subset of a cartesian product. If a function is a

Date: Fri, 11 Jan 2008 09:12:15 +0100

Message-ID: <478723c5$0$85785$e4fe514c_at_news.xs4all.nl>

David BL wrote:

> Keith H Duggar wrote:

>> David BL wrote: >>> Marshall wrote: >>>> An interesting note, by the way: functions are relations...

>>> Isn't it more precise to say that the graph of a function is a >>> relation?

>> No, it isn't. >> >> http://mathworld.wolfram.com/Function.html

*>**> From mathworld a relation**>**> http://mathworld.wolfram.com/Relation.html**>*> is defined as a subset of a cartesian product. If a function is a

*> relation why do they define a graph of a function f as**>**> { (x,f(x)) | x in domain of f },**>**> as described in**>**> http://mathworld.wolfram.com/FunctionGraph.html*That is 'graph' meaning 'plot', not 'a collection of vertices and edges'. In cdt it is the latter meaning that is mostly used (when discussing network and hierarchical databases).

-- We do this all the time. In theory, it's not going to work.Received on Fri Jan 11 2008 - 09:12:15 CET