Home -> Usenet -> comp.databases.theory -> Understanding Logics with Aggregate Operators

Understanding Logics with Aggregate Operators

From: arthernan <arthernan_at_hotmail.com>
Date: 25 Jan 2007 14:06:57 -0800
Message-ID: <1169762817.304743.61000_at_q2g2000cwa.googlegroups.com> 





I agree with the saying "go to the source". So I did. I do database
programming for a living. And I want to know what else is out there,
that is based in formal methods. I just hear that there is all this
great research already done and we are not using it.



Aggregates seem to be one missing piece in most logic description
languages. So I decided to look up articles in the subject and I found
this one.



Logics with Aggregate Operators. (2000) (Lauri Hella).



I read the first four pages just fine, but I am stuck (for now) on page
5. Anyway here is my problem:



Notes: 1)The link to the original PDF article is at the bottom. 2) The
symbol φ in case it's hard to read here is the Greek letter phi)



I'm not sure what this formula means



t(x) = y.φ(x,y)      (x and y have a vector sign on top of them)



And then from there I think I am also missing.



Aggr f y.(φ(x,y),t(x,y))



I don't think I know which one is the free variable.



I think I could understand this article, but I'm not sure where to look
or if a clarification is what I need. In any case any information is
greately appreciated.




http://tinyurl.com/2qe7p6



or



http://preview.tinyurl.com/2qe7p6
Received on Thu Jan 25 2007 - 23:06:57 CET












Original text of this message