9. A computer-implemented method for providing an information navigation system for searching a set of materials having navigation states, the method comprising: providing information including: the set of materials, a plurality of attributes characterizing the materials, a plurality of values describing the materials, each value of the values having an association with at least one attribute of the attributes, each association defining an attribute-value pair, and a plurality of navigation states, each navigation state corresponding to a particular set of attribute-value pairs and to a particular subset of materials, wherein the particular subset of materials consists of materials in the information navigation system that are described by every attribute-value pair in the particular set of attribute-value pairs corresponding to said each navigation state, such that each material of materials in the particular subset of materials is described by every attribute-value pair in the particular set of attribute-value pairs corresponding to said each navigation state; using a data structure in a memory to permit at least some navigation states of the plurality of navigation states to be computed dynamically, wherein a first navigation state of the computed navigation states includes a first attribute-value pair having a first attribute, in which the first attribute-value pair does not describe all the materials in the navigation system that the first attribute characterizes, wherein a second navigation state of the computed navigation states includes a second attribute-value pair having the first attribute, in which the second attribute-value pair refines the first attribute-value pair, and wherein at least one of the first navigation state and the second navigation state includes a third attribute-value pair having a third attribute, which is not the same as the first attribute, wherein the third attribute-value pair is mutually incomparable with the first attribute-value pair and is mutually incomparable with the second attribute-value pair, and the third attribute-value pair does not describe all the materials in the navigation system that the third attribute characterizes; providing an interface to the navigation system, the interface including a free-text search tool, and the interface providing a plurality of transitions, each transition providing a direct path, with no intervening navigation states, between two of the navigation states, wherein said each transition represents a change from a set of attribute-value pairs corresponding to an originating navigation state to the set of attribute-value pairs corresponding to a destination navigation state, wherein series of one or more transitions provides a path between any two navigation states, there being more than one path between at least a third navigation state and a fourth navigation state, wherein the interface includes a guided search tool for enabling navigation from a current navigation state based on the plurality of transitions among the plurality of navigation states, and wherein the interface operates in an XML-based environment; searching, by using a computer, descriptive information associated with the set of materials, based at least in part on a free-text query accepted from the free-text search tool of the provided interface, to produce a set of free-text query interpretations; accepting a query to the information navigation system based at least in part on the free-text query interpretations; generating a responsive navigation state using the data structure based on the query; and presenting the responsive navigation state to a user.
9. A computer-implemented method for providing an information navigation system for searching a set of materials having navigation states, the method comprising: providing information including: the set of materials, a plurality of attributes characterizing the materials, a plurality of values describing the materials, each value of the values having an association with at least one attribute of the attributes, each association defining an attribute-value pair, and a plurality of navigation states, each navigation state corresponding to a particular set of attribute-value pairs and to a particular subset of materials, wherein the particular subset of materials consists of materials in the information navigation system that are described by every attribute-value pair in the particular set of attribute-value pairs corresponding to said each navigation state, such that each material of materials in the particular subset of materials is described by every attribute-value pair in the particular set of attribute-value pairs corresponding to said each navigation state; using a data structure in a memory to permit at least some navigation states of the plurality of navigation states to be computed dynamically, wherein a first navigation state of the computed navigation states includes a first attribute-value pair having a first attribute, in which the first attribute-value pair does not describe all the materials in the navigation system that the first attribute characterizes, wherein a second navigation state of the computed navigation states includes a second attribute-value pair having the first attribute, in which the second attribute-value pair refines the first attribute-value pair, and wherein at least one of the first navigation state and the second navigation state includes a third attribute-value pair having a third attribute, which is not the same as the first attribute, wherein the third attribute-value pair is mutually incomparable with the first attribute-value pair and is mutually incomparable with the second attribute-value pair, and the third attribute-value pair does not describe all the materials in the navigation system that the third attribute characterizes; providing an interface to the navigation system, the interface including a free-text search tool, and the interface providing a plurality of transitions, each transition providing a direct path, with no intervening navigation states, between two of the navigation states, wherein said each transition represents a change from a set of attribute-value pairs corresponding to an originating navigation state to the set of attribute-value pairs corresponding to a destination navigation state, wherein series of one or more transitions provides a path between any two navigation states, there being more than one path between at least a third navigation state and a fourth navigation state, wherein the interface includes a guided search tool for enabling navigation from a current navigation state based on the plurality of transitions among the plurality of navigation states, and wherein the interface operates in an XML-based environment; searching, by using a computer, descriptive information associated with the set of materials, based at least in part on a free-text query accepted from the free-text search tool of the provided interface, to produce a set of free-text query interpretations; accepting a query to the information navigation system based at least in part on the free-text query interpretations; generating a responsive navigation state using the data structure based on the query; and presenting the responsive navigation state to a user. 46. The method of claim 9 , wherein navigation options include a presentation of a set of lists of attribute-value pairs, each list corresponding to one of the attributes, some lists including attribute-value pairs that refine the attribute-value pairs corresponding to the current navigation state and some lists including attribute value pairs that are incomparable to the attribute-value pairs corresponding to the current navigation state.