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Re: XML query constructors: not well-defined

From: Dan Connolly <connolly@w3.org>
Date: Thu, 03 May 2001 05:43:25 -0500
Message-ID: <3AF1364D.29FDC1DE@w3.org>
To: "Mary F. Fernandez" <mff@research.att.com>, Michael Rys <mrys@microsoft.com>
CC: www-xml-query-comments@w3.org
This clarifies things, but it's not what I was hoping for...

"Mary F. Fernandez" wrote:
> 
> Dear Dan,
> 
> This is a response to the following message, which you posted to the XML
> Query Working Group's comments list:
> 
> 
> http://lists.w3.org/Archives/Public/www-xml-query-comments/2001Apr/0014.html
> 
> The XML Query Working Group has approved the following response:
> 
>     The next draft of the data model includes the following text to
>     address your question about node identity:
> 
>     "Each kind of node has its own constructor. The effect of a node
>     constructor is to create a new node with a unique identity,
>     distinct from all other nodes."
[...]

OK, that clarifies the intent, but...

>     You are correct that a node constructor is not function in the
>     mathematical sense, because it has the side effect of creating a
>     node with a unique identity.

Bummer. I really would like to have an XML data model with
constructors that I can use in traditional math settings,
with substitution-of-equals-for-equals and all that.

I ran into Michael Rys at the conference, and he started
to explain that I could look at these operators as
producing new monads or some such, but I don't understand
enough background to get it. I'd appreciate pointers
to background reading on monads or whatever.

[...]

> We appreciate your feedback on the XML Query specifications. Please let
> us
> know if this response is satisfactory. If not, please respond to this
> message, explaining your concerns.

I'm not sure yet...

Maybe you can explain this monad stuff so that I can use
the design as specified above in traditional math settings.

I'm going to keep an eye out for use-cases where this really
matters. Maybe it's just a matter of taste and I'll learn
to live with it.

-- 
Dan Connolly, W3C http://www.w3.org/People/Connolly/
Received on Thursday, 3 May 2001 06:43:48 GMT

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