I could go with yes|no|unknown, but then we'd have to find another name for the attribute. We already have a pretty good mechanism, widely available, for dealing with certainty.

<trait type="fauna" subtype="snakes" present="false" cert="high" resp="#StPatrick"><p>There are no snakes to be found anywhere on the island.</p></trait>

The real question, though, is whether anybody, apart from me, sees the potential usefulness of such a mechanism. If so, we can then try to come up with one (or repurpose an existing one).

Matthew

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Fra: TEI (Text Encoding Initiative) public discussion list [mailto:[log in to unmask]] På vegne af Sebastian Rahtz
Sendt: 10. februar 2010 12:32
Til: [log in to unmask]
Emne: Re: Indicating the presence or absence of a feature

> <place>
> <placeName>Ireland</placeName>
> <trait type="fauna" subtype="snakes" present="false"><p>There are no snakes to be found anywhere on the island.</p></trait>

I worry about this; isn't the range more detailed than true/false?

    There are snakes, we have evidence
     We have not seen any snakes, so we assume there are none
     We have not looked to see if there are snakes, so we don't know if there are or not
     We know that there cannot be any snakes (cos there is no air)
--
Sebastian Rahtz      
(acting) Information and Support Group Manager
Oxford University Computing Services
13 Banbury Road, Oxford OX2 6NN. Phone +44 1865 283431

Sólo le pido a Dios
que el futuro no me sea indiferente