These are difficult to convey in English. (a) Don (A) is crushing a soda can (P). (b) Don (S) is crushing. [with the implication that a soda can is being crushed]. Note that this is not the same as an ambitransitive verb, which can be either intransitive or transitive (see criterion 4 below, which this does not meet). There are some problems, however, with the terms passive and antipassive because they have been used to describe a wide range of behaviors across the world's languages. For example, when compared to a canonical European passive, the passive construction in other languages is justified in its name. However, when comparing passives across the world's languages, they do not share a single common feature. R. M. W. Dixon has proposed four properties of passives and antipassives. They apply to underlying transitive clauses and form a derived intransitive. The underlying P of the passive and A of the antipassive become S. The underlying A of the passive and P of the antipassive go into the periphery and are marked by a non-core case/preposition/etc. These can be omitted, but there's always the option of including them. There is some explicit marking of the construction. He acknowledges that this excludes some constructions labeled as "passive" by some linguists. Other ways to reduce valency include the reflexives, reciprocals, inverse constructions, middle voice, object demotion, noun incorporation, and object incorporation. Valency-increasing This involves moving an argument from the periphery into the core. Applicatives and causatives are prototypical valency increasing devices. In syntactic theory Valence plays an important role in a number of the syntactic frameworks that have been developed in the last few decades. In generalized phrase structure grammar (GPSG), many of the phrase structure rules generate the class of verbs with a particular valence. For example, the following rule generates the class of transitive verbs: VP → H NP [love] H stands for the head of the VP, that is the part which shares the same category as the VP, in this case, the verb. Some linguists objected that there would be one such rule for every valence pattern. Such a list would miss the fact that all such rules have certain properties in common. Work in government and binding (GB) takes the approach of generating all such structures with a single schema, called the X-bar schema: X′ → X, Y″... X and Y can stand for