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.
5. The method of claim 2 , wherein choosing the form of attributive expressions includes constructing an application-specific form that is designed based on a set of supported logical operations to be used for defining classification categories, wherein: a) the sequence of specializations encoded by each application-specific attributive expression strictly corresponds to the recurrent descriptions of criteria root categories so that each attributive expression can be derived from the empty attributive expression by means of a number of recurrent specializations satisfying the limitations of criteria applicability; and b) no one criterion can be used for specialization until its root category is explicitly defined, while each criterion with a predefined root category is available for specialization from a given category if and only if the root category includes the category, and the attributive expression of the category does not already include a complete specialization by the criterion.