j


i

          2-8


          applicable to both statistical and semantic processing since the meaning

          0 a word is ~enerally invariant over its morphological variants.  Much

          more ambitious syntactic processing procedures are also under *

          investigation, including the use 0 ully automatic syntactic analysis.

          A ull sentence by sentence syntactic analysis could, or example,

          provide explicit dependency relations among the various semantic

          elements 0 a sentence, and could be us~ed or phrase recogaition or or

          the reco~rijtion 0 structurally constrained associations among semantic

          terms.  At thepresent time it~is not clear whether the complexity

          ~e~uired or the reco~riition 0 complex structural constraints is

          justiied in terms 0 the additional inormation extracted thereby.


          4.  The Structure 0 Index Representations


                   The index transormation represents a mapping rom the natural

          langua~ 0 the source text to the tar~t or index la~~e.        The index

          ima~e 0 a source document is thus a representation 0 the content 0

         * the document~in this target langnagee~ The most commonly used index

         * lai~ge structure is the description list, or property vector, in

          which the indez image consists 0 a list 0 those properties 0 a inite

          set which characterize'the document.   Index images 0 this type are

          used, or example, in Uniterm systems~where the document representation

          is an unordered set of keywords (descriptors,,uniterms, etc.).  1 the

          property set is~ordered, or example, by a 1 to 1 mapping to the set 0

        * integers, the index image may be encoded as a binary vector.   A more

          general. representation 0 the same type allows or a quantization 0 the