2. A computer-implemented method for building a polyhierarchical classification of objects, comprising: a) identifying a plurality of criteria for specializing the objects based on their properties, wherein each criterion of the plurality of criteria is defined by a set of mutually exclusive attributes, wherein each attribute describes one or more properties of the objects; b) recurrently defining a root category for each criterion in terms of an attributive expression representing a logical composition of one or more attributes of criteria whose root categories have been previously defined in the recurrent sequence, or the empty attributive expression; wherein no one criterion participates in the definition of its own root category, and each attributive expression encodes a sequence of specializations by criteria so that the root category of each following criterion includes the category represented by the sequence of all previous specializations; c) storing in a computer-readable medium the plurality of criteria and their root categories in the form of attributive expressions; and d) using the stored plurality of criteria for polyhierachically structuring, updating and accessing information associated with the objects.
2. A computer-implemented method for building a polyhierarchical classification of objects, comprising: a) identifying a plurality of criteria for specializing the objects based on their properties, wherein each criterion of the plurality of criteria is defined by a set of mutually exclusive attributes, wherein each attribute describes one or more properties of the objects; b) recurrently defining a root category for each criterion in terms of an attributive expression representing a logical composition of one or more attributes of criteria whose root categories have been previously defined in the recurrent sequence, or the empty attributive expression; wherein no one criterion participates in the definition of its own root category, and each attributive expression encodes a sequence of specializations by criteria so that the root category of each following criterion includes the category represented by the sequence of all previous specializations; c) storing in a computer-readable medium the plurality of criteria and their root categories in the form of attributive expressions; and d) using the stored plurality of criteria for polyhierachically structuring, updating and accessing information associated with the objects. 23. The method of claim 2 , further comprising extracting user-specified sub-hierarchies in the induced polyhierarchy of classification categories, wherein the user-specified sub-hierarchies are automatically restored during run-time using algorithms for retrieving direct child categories and direct parent categories of selected classification categories, wherein the direct child and parent categories of the selected categories are defined by the structure of the generating polyhierarchy of criteria and depend on the chosen form of attributive expressions.