In this section I will give some examples of the use of a unification grammar (in PATR II  notation) to define the relation between language dependent logical forms. For illustrative purposes I will assume logical forms are represented by feature structures consisting of the attributes , , together with some attributes representing `universal' meanings such as tense, aspect, number and person; I will not touch upon issues such as quantification and modification. The logical forms of English and Spanish are labeled by the attributes and respectively. As an example the logical form of `The army opened fire at the civilians' is represented as in figure 1.
Such feature structures will often be related in a straightforward way to a Spanish equivalent, except for the value of the attributes. A very simple rule in PATR II style may look as in figure 2.
This rule simply states that the translation of a logical form is composed of the translation of its arguments. If the rule applies to the feature structure in 1 the three daughters of the rule will be instantiated as in figure 3, and the value of will be bound to the values of these daughters.
An example of the rule for the first daughter will be a lexical entry and looks as in figure 4.
A lexical entrylexical 0 0 gb = open_fire_at 0 sp = romper_el_fuego_a The simple English expression `army' has to be translated as a complex expression in Spanish: `fuerza militar'. The rule will look as in 5 where it is assumed that the construction is analyzed in Spanish as an ordinary noun-adjective construction, and where the logical form of the adjective takes the logical form of the noun as its argument. A rule for `fuerza militar'army 0 0 gb pred = army 0 sp pred pred = militar 0 sp arg1 pred = fuerza 0 sp arg1 number = 0 gb number The translation for `civilian' is defined in a similar rule (although the translation of `number' is different). Note that this example of complex transfer is similar to the famous `schimmel - grey horse' cases. As a result of the rule applications the feature structure in figure 1 will get instantiated to the feature structure in 6, from which the generator generates the string `La fuerza militar rompio el fuego a la poblacion civil'.
In the foregoing examples the relation between logical forms is rather straightforward. Note however that the full power of a unification grammar can be used to settle more difficult translation cases, because different attributes can be used to represent the `translational syntax'. For instance we can build a tree as value of the attribute to represent the derivational history of the translation process. Or we can `thread' information through different nodes to be able to make translations dependent on each other. Translation parameters such as style and subject field can be percolated as attributes of nodes to obtain consistent translations; but these attributes themselves need not be translated.