Proceedings - Österreichische Gesellschaft für Artificial Intelligence

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WORDFORM ‘der’
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⎢AGREEMENT 1 ⎢
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AGREEMENT 1
Figure 2: Example of a typed feature structure with
structure sharing.
tween different applications. In what follows, we
first give a formal definition of feature structures.
Section 2 is concerned with the rationale behind
the XML representation defined by the standard,
while Section 3 gives an overview of the elements
of the standard itself. In the concluding Section 4,
we will briefly discuss how this standard is related
to other standardization proposals for language
resources and what role the standard can
play for application programming.
1.2 Formal definition of feature structures
In Part 2 of the International Standard ISO 24610,
feature structures are formally defined as follows.
The definition presumes a given finite set F of
features, a finite type hierarchy T with subtyping
relation < and a set X of “built-in” elements (see
below). 2
Definition A feature structure over F, T and X
is a quadruple 〈Q, ρ, θ, δ〉, in which
– Q is a set of nodes,
– ρ is an element of Q, called the root,
– θ is a partial typing function from Q to T ,
– δ is a partial feature value function from F ×Q
to Q ∪ X ,
such that, for every node q ≠ ρ, there exists a
sequence f 1 , . . . , f n of features and a sequence
q 1 , . . . , q n of nodes with q 1 = ρ, q n = q and
q i+1 = δ(f i , q i ) for i < n.
2 A type hierarchy is a finite ordered set 〈T ,