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Sequence type and other related questions

From: Paul Duffin <pduffin@volantis.com>
Date: Tue, 15 Jul 2003 11:03:18 +0100
Message-ID: <3F13D166.5030309@volantis.com>
To: www-ql@w3.org

The section on sequences 
(http://www.w3.org/TR/xpath-datamodel/#sequences) states that a sequence 
that contains a single item is indistinguishable from the item itself. 
Among other things this means that a sequence with one item in it has 
the same type as that item. Therefore sequences must have types.

This raises a couple of questions.

What is the type of a sequence with two (or more) items in it which are 
potentially different ?

Is it just a generic sequence type, is it the type which is the closest 
ancestor of all the item types, or something else ?

What is the type of an empty sequence ?

Can the empty sequence be a singleton, i.e. are all empty sequences the 
same ? There was an issue raised that asked for empty sequences to be 
typed but the resolution was private.

Apologies if these questions have already been answered elsewhere. I 
have looked and could not find anything.
Received on Tuesday, 15 July 2003 06:03:46 UTC

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