Dear Roger,
I
could not reall yunderstand what you and Kevin mean by Characters and
States.
From the example you gave, it appears to be like classes
(character) and attributes (states) or you want to assign GUIDs to
something like Thesaurus entries? But maybe I
completely misunderstood what you meant..
best regards,Robert
Kevin mentioning Characters and States and
GUIDs got me thinking and I was wondering if we could cover something
along these lines before the meeting. Please excuse me if this has been
dealt with on the list. I will use a Delta type illustration to my point.
This may not apply to SDD so much - apologies if it doesn't but I am
trying to get at a general point. My comments may be more general to GUIDs
though...
When we are dealing with GUIDs we are talking in an Open
World model as opposed to a Closed World model. If I search Google (open
world) and don't find something it isn't because it doesn't exist - it may
exist but not be found for a host of reasons. If I search my local SQL DB
(closed world) and I don't find something then I can safely assume it
isn't there. (This may be a naive description of Open vs Close worlds but
it illustrates the point).
Taking this to the Characters/States
model. We have a character that looks like this:
Flower Colour
(GUID_c01)
- red (GUID_s01)
- white (GUID_s02)
- yellow
(GUID_s03)
And I score a taxon as "Rose has flower
colour red". If I have given GUIDs to the states then I don't need to use
the GUID for the character. "Rose has s01" is fine as the character is
implied.
Can we assume from this statement that my rose does not
have white or yellow flowers? Yes - but only if it is a closed world and
we know that the character never changes (or hasn't changed since the date
of the assertion). If the choice when scoring had been:
Flower
Colour (GUID_c01)
- red (GUID_s01)
- white (GUID_s02)
- yellow
(GUID_s03)
- dark pink (GUID_s99)
I may have chosen "Rose has
s99" of "Rose has s99 and s01" but I simply didn't have that choice
before.
So the thing that is troubling me is that Character/State
uses a closed world model where not finding something implies that it
doesn't have that attribute. In an open world system one can only draw
conclusions from presence not absence. We could give GUIDs to characters
and states but it doesn't get us very far as it doesn't permit us to
re-use or extend them in a simple way. (sure you could build an
inheritance model for characters and states but this rapidly becomes a
complete ontology language of which there are a few already
available!).
My gut feeling is that in the long term the
Character/State model doesn't transfer well into an open world model. I
suspect this problem may occur in other descriptive areas where the
existing model specifies noun-adjective pairs that I don't have experience
of. Perhaps we could explore this a little. Perhaps my guts need
straightening out!
Your thoughts greatly
appreciated.
Roger
--
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Roger Hyam
Technical Architect
Taxonomic Databases Working Group
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http://www.tdwg.org
roger@tdwg.org
+44 1578 722782
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