Jean-Marc Vanel wrote under the Subject: RDF Schema design pb: inheritance of properties (Subject renamed, because this post refers to issues secondary to the original post)

There is a containment hierarchy (e. g. a flower contains petals)

which

raises no problems in XML.

I would like to challenge this assumption, which seems to be generally accepted in the discussion here.

It is true: Morphological structures may have containment hierarchies, but I believe that these depent strongly on the viewpoint of the author or user.

EXAMPLE 1: The peduncle (stalk of a flower) is usually assumed to be part of the flower, but anatomically it is clearly a part of the stem (in contrast to the petiole, stalk of a leaf!).

EXAMPLE 2: Stuff can be in-between: The inflorescence contains part of stem, part of leaves, and all flowers. Which leaves are part of inflorescens and thus called bracts, and which aren't is often a matter of taste, school, country...

Thus: there are multiple concurrent or competing hierarchies, which may overlap.

EXAMPLE 3: Further, other, non-morphological hierarchies/classifications exist. These may be much more relevant for many purposes, and may be the primary outline used in a natural language description. For example, structures can be classified by function (sexual/asexual propagation), observation method (naked eye/light microsc./electron microscopy, physiological/molecular etc.

EXAMPLE 3 (leaving morphology altogether): Gene sequences can be classified as transscribed/non-transscribed, Protein-coding/rRNA coding/non-coding, intron/exon, regulatory/structural, conserved/variable/hypervariable etc. Most of these classifications overlap.

*** Call for more examples: Can anybody come up with more good examples (perhaps from animals) as to why a fixed hierarchy in the form of a feature path may be unpractical?

Info. for computer men: biology has a hierarchic classification of species whose 4 lowest levels are: order family genus species

Sorry this is a gross misrepresentation. Info from a biologist:

(incomplete list, reflecting botanical code, and devised with fungi in mind). Number of ranks is a matter of taste, some people like to supra and sub [and hyper+hypo? :-) ] everything:

CODE Description fsp. forma specialis nov. -- nomenclatorially facultative subfm. subforma nov. -- subform nomenclatorially obligatory fm. forma nov. -- form nomenclatorially obligatory subvar. subvarietas nov. -- sub-variety nomenclat. obligatory var. varietas nov. variety nomenclatorially obligatory ssp. subspecies nov. subspecies priority mandatory sp. species nov. -- species priority mandatory subser. subseries nov. -- subseries priority mandatory ser. series nov. -- section priority mandatory subsect. subsectio nov. -- subsection priority mandatory sect. sectio nov. -- section priority mandatory subgen. subgenus nov. -- subgenus priority mandatory gen. genus nov. -- genus priority mandatory subtrib. subtribus nov. -- subtribus priority mandatory trib. tribus nov. -- tribus priority mandatory subfam. subfamilia nov. -- subfamily priority mandatory fam. familia nov. -- family priority mandatory superfam. superfamilia nov. -- super-family priority mandatory subord. subordo nov. -- suborder priority facultative ord. ordo nov. -- order priority facultative superord. superordo nov. -- superorder priority facultative subclass. subclassis nov. -- subclass priority facultative class. classis nov. -- class priority facultative subdiv. subdivisio nov. -- subdivision priority facultative div. divisio nov. -- division priority facultative subreg. subregnum novum. -- sub-regnum priority facultative reg. regnum novum. -- regnum priority facultative

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

Often wrong but never in doubt!