Uniqueness Principle and contextual tags

When contextual PoS tags are used to define a pattern, it is necessary to take into account whether the contextual tags are or not syntactically related to the dependent tag of the pattern. For instance, take this rule:

AdjunctLeft : [DT]? [ADV]? ADJ NOUN

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The contextual tags, [ADV] and [DT], have significant differences. While [ADV] is syntactically related to the adjective, which is the dependent, [DET] is linked to the noun, the head of the dependency. So, if this rule is applied, it will not be possible to identify later the dependency between the adverb and the adjective, given that the adjective has already been removed from the input string. However, as [DT] is related to the head, the dependency between DT and NOUN can be identfied later by using the corresponding rule.

In order to identify as many dependencies as possible, the grammar should contain rules with contextual tags that are not related to the dependent. Otherwise, some possible dependencies will be missed.

So considering the Uniqueness principle and the contextual tags, the user must take into account the following constraint to build well-formed DepPattern grammars:

Constraint 2: No contextual tag must be related to the dependent tag of a rule.