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C00002 00002	label[w86,jmc]		Labelled sentences
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label[w86,jmc]		Labelled sentences

One way of handling prevention involves labelling sentences and letting
one sentence cancel another by referring explicitly to its label.
However, it seems inadequate to allow only cancelling the sentence
entirely.  Rather we must provide for cancelling its application to
a particular case.  There are several possible ways of doing this.

1. The sentence is labelled  foo(x,y).  Effectively this amounts
to imbedding the label in an outer level quantifier.  Then we can
have  cancel(foo,term1,term2)  as a conclusion.

2. We write  because(foo,p)  instead of writing  p.  This may enable
cancelling  foo  prevent  p  from being concluded.