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In this section, we very briefly introduce the idea of the selection constraint for finite domains. It has the form:

`I={Select.fd [I1 I2 ... In] K}`

where `I`

, `I1`

, ..., `In`

, `K`

are all FD variables (possibly determined, i.e. integers). Its declarative semantics is that . Constraint propagation can affect both `I`

and `K`

: if `Ip`

cannot be equal to `I`

(i.e. their domains are disjoint), then `p`

is removed from the domain of `K`

. Furthermore, the domain of `I`

must be a subset of the union of the domains of `Ip`

for `p`

in the domain of `K`

. To learn more about the selection constraint, see Section 6.9 and also the treatment of dependency parsing in Chapter 5.

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Denys Duchier

Version 1.2.0 (20010221)