[tdwg-tag] SPM Categories or Subclassing - again.

Gregor Hagedorn g.m.hagedorn at gmail.com
Mon Oct 8 14:41:39 CEST 2007

In SDD we used what is here called the "tagging approach", i.e. for
descriptive concepts and characters we use

<Text ref="some.resource.org/123"><Content>Free form text</Content></Text>

In SDD, all element/attribute names refer to classes/attributes in UML or
Java, whereas the xml values are corresponding values. Expressing concepts
and characters as classes was considered impractical if the aim is generic
software (classes are creatable at runtime, but at a price) because the
number of characters is often very large.

My experience shows that the number of character in identification sets
varies between 50 and over 1000. Some studies in manual data integration (in
LIAS) convinced me that the number of "integratable" characters is often
less than imagined. A similar case study may also be the FRIDA data sets,
which limit the number of common characters (common to all plant families)
to 200, and from thereon use separate characters for each family.

Clearly, when limiting the approach to just "very high level concepts", both
class and value approaches are possible. The benefit of the SPM 0.2 approach
is that it does enable reasoning (as well as may simplify tapir usage).
However, as presented in Bratislava, I am doubtful that this limit holds. In
my experience the limit between free form text and categorical data tends be
diffuse rather than sharp and my intuition is that the SPM mechanism, being
extensible, will be extended.

I would like to note that the current TAG strategy is to provide both RDF
and xml schema. The schema approach to SPM, however, seems to be more and
more undesirable as the number of descriptive concepts grows.

I have a question for TAPIR:

Does TAPIR find it easier to search elements having specific attribute
values than elements having child elements with specific value:

 <InfoItem category="voc.x.org/DescriptiveConcepts/Size<http://some.resource.org/123>">


I might be useful to know. Although RDF allows this for literals, it seems
to require the rdf:resource="" step for categorical data, so this may or may
not help.


PS: SDD calls the concepts "characters" based on the tradition and character
is clearly inappropriate. However, Category to me seems to express nothing
other than the type of the value. All contextValue and Value in SPM in
version 0.2 refer to categories. Can anyone suggest a better term? What is
the opposite of "value"?

I can think of "Class" (value = instance), or - but perhaps too much limited
to descriptions - "Feature" (also in GML). Anything else?


Gregor Hagedorn (G.M.Hagedorn at gmail.com)
Institute for Plant Virology, Microbiology, and Biosafety
Federal Research Center for Agriculture and Forestry (BBA)
Königin-Luise-Str. 19      Tel: +49-30-8304-2220
14195 Berlin, Germany      Fax: +49-30-8304-2203
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