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

          justi£ied in terms 0£ the additional in£ormation extracted thereby.


          4.  The Structure 0£ Index Representations


                   The index trans£ormation 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