Re: interleave and strings

[James Clark <jjc@jclark.com>]

There's a restriction described in the tutorial (end of section 6) and
implemented in my sample implementation, but not yet described in the
spec (5.2 is a placeholder), that makes this illegal.

Say that a pattern p "distinguishes strings" if:

- p matches t1 and
- p matches t2 and
- t1 and t2 differ only in their character children

(ie p contains <string> or <data> patterns; containing <anyString> alone
does not make p distinguish strings).

Say that a pattern p "allows children" if there exists a tree t such
that p matches t and t has non-empty children (and not all whitespace).

Then the restriction is that

  <group>p1 p2</group>

is not allowed if

- p1 distinguishes strings, and
- p2 allows children

or vice-versa.  Similarly for interleave and for any pattern that
implicitly groups.  So for

  <oneOrMore>p</oneOrMore>

it's an error if p distinguishes strings.

Murata Makoto wrote:
> 
> Consider a patter as below:
> 
> <interleave><anyString/><string>true</string></interleave>
> 
> In my understanding, this matches "true", "0t0r0u0e", "1111t8rtu2342e".
> 
> Another example:
> 
> <interleave><data type="xsd:integer"/><string>13</string></interleave>
> 
> This matches "1234", since it is an interleaving of "24" and "13", where
> "24" is an integer.
> 
> I think that this makes implementation very difficult or even impossible.
> Furthermore, I see no values in allowing such patterns.
> 
> Cheers,
> 
> Makoto