MULTISTAGE CHARACTER OF THE MEANING Û TEXT TRANSFORMER

FIGURE IV.10. Levels of linguistic representation.


The ambiguity of the Meaning Û Text mapping in both directions, as well as the complicated structure of entities on both ends of the Meaning Û Text transformer make it impossible to study this transformer without dividing the process of transformation into several sequential stages.

Existence of such stages in natural language is acknowledged by many linguists. In this way, intermediate levels of representation of the information under processing are introduced (see Figure IV.10), as well as partial transformers for transition from a level to an adjacent (see Figure IV.11).

Two intermediate levels are commonly accepted by all linguists, with small differences in the definitions, namely the morphologic and syntactic ones.

FIGURE IV.11. Stages of transformation.


In fact, classical general linguistics laid the basis for such a division before any modern research. We will study these levels later in detail.

Other intermediate levels are often introduced by some linguists so that the partial transformers themselves are divided into sub-transformers. For example, a surface and a deep syntactic level are introduced for the syntactic stage, and deep and a surface morphologic level for the morphologic one.

Thus, we can imagine language as a multistage, or multilevel, Meaning Û Text transformer (see Figure IV.12).

The knowledge necessary for each level of transformation is represented in computer dictionaries and computer grammars (see Fi­gure IV.13). A computer dictionary is a collection of information on each word, and thus it is the main knowledge base of a text processing system. A computer grammar is a set of rules based on common properties of large groups of words. Hence, the grammar rules are equally applicable to many words.

Since the information stored in the dictionaries for each lexeme is specified for each linguistic level separately, program developers often distinguish a morphologic dictionary that specifies the morphologic information for each word, a syntactic dictionary, and a semantic dictionary, as in Fi­gure IV.13.

FIGURE IV.12. Interlevel processing.


In contrast, all information can be representedin one dictionary, giving for each lexeme all the necessary data. In this case, the dictionary entry for each lexeme has several zones that give the properties of this lexeme at the given linguistic level, i.e., a morphologic zone, syntactic zone, and semantic zone.

Clearly, these two representations of the dictionary are logically equivalent.

According to Fi­gure IV.13, the information about lexemes is distributed among several linguistic levels. In Text, there are only wordforms. In analysis, lexemes as units under processing are involved at morphologic level. Then they are used at surface and deep syntactical levels and at last disappeared at semantic level, giving up their places to semantic elements. The latter elements conserve the meaning of lexemes, but are devoid of their purely grammatical properties, such as part of speech or gender. Hence, we can conclude that there is no level in the Text Þ Meaning transformer, which could be called lexical.