RE: [xml-dev] Grand Challenge: the same query, independent of howdata re

["Costello, Roger L." <costello@mitre.org>]

Michael Kay wrote:

	You can encapsulate all three mechanisms 
	behind a function (or two functions, one for 
	each direction of the relationship).

What do you mean by "function"? 

Do you mean a user-defined XPath function?

How would such a user-defined function work? Would one have to provide it some indication of the relationship? For example, 

	Hey function, give me the Title of the Book
	written by Richard Bach, where the Title is
	contained within Book (or the Title is referenced
	by an intra-document link, or the Title is
	referenced by a cross-document link).

Is that what you mean? If yes, would you sketch out such a user-defined XPath function please?

/Roger


-----Original Message-----
From: Michael Kay [mailto:mike@saxonica.com] 
Sent: Thursday, February 20, 2014 9:30 AM
To: Costello, Roger L.
Cc: xml-dev@lists.xml.org
Subject: Re: [xml-dev] Grand Challenge: the same query, independent of how data relationships are modeled

> 
> Fascinating!
> 
> So, we want to be able to express:
> 
> 	Give me the Title of the Book that was written by 
> 	Richard Bach.
> 
> and that should give us the correct answer, regardless of how the Book/Title relationship is modeled. 
> 
> Right?
> 
> How do we achieve this?
> 

You can encapsulate all three mechanisms behind a function (or two functions, one for each direction of the relationship), and I would certainly recommend doing that in many cases.

Michael Kay
Saxonica