Here, we make this dependency relation explicit. But especially in the rule above, the contextual test is far from being sufficient to select the subject reading reliably. Instead, it leaves open a possibility to attach a dependency from another syntactic function, i.e. the dependency relations remain ambiguous. The grammar tries to be careful not to introduce false dependencies but for an obvious reason this is not always possible. If several syntactic functions of a word have dependency relations, they form a dependency forest.
Links formed between syntactic labels constitute partial trees, usually around verbal nuclei.
But a new mechanism is needed to make full use of the structural information provided by multiple rules. Once a link is formed between labels, it can be used by the other rules. The following rule establishes a dependency relation of a verb and its object complement, if the object already exists.