A computer program product, residing on a computer-readable medium, for navigating a knowledge base, the computer program product comprising instructions configured to cause a computer to: access a knowledge base comprising: a collection of objects to be searched and retrieved during interaction with the system; a faceted classification system, wherein each object is associated with an arbitrary number of facet values describing the object, and wherein at least one facet is associated with a hierarchy of values; and a set of relationships defined between pairs of objects in the knowledge base, wherein each relationship links an object to a related object via a connection specified by name, and wherein said object relationships are implemented using facet values; compute a navigation state including a subset of the objects in the collection in response to interaction with the navigation system, wherein said computation of a navigation state supports path operators specifying a relationship R and an expression E to denote a set of objects related by the relationship R to one or more of the objects in the set specified by E; generate a representation of the navigation state; and compute a set of refinements for the navigation state based on facets of objects related to the subset of objects by at least one of the set of relationships; wherein the instructions for causing the computer to compute the set of refinements for the navigation state include instructions for causing the computer to identify facets describing the objects related to the subset of objects and instructions for causing the computer to execute rules for bounding the computation of the set of refinements, said rules comprising path restriction rules that place a limit on the relationship path expressions that will be included in refinements, said limit specifying an absolute bound on the number of relationship links traversed. access a knowledge base comprising: a collection of objects to be searched and retrieved during interaction with the system; a faceted classification system, wherein each object is associated with an arbitrary number of facet values describing the object, and wherein at least one facet is associated with a hierarchy of values; and a set of relationships defined between pairs of objects in the knowledge base, wherein each relationship links an object to a related object via a connection specified by name, and wherein said object relationships are implemented using facet values; a collection of objects to be searched and retrieved during interaction with the system; a faceted classification system, wherein each object is associated with an arbitrary number of facet values describing the object, and wherein at least one facet is associated with a hierarchy of values; and a set of relationships defined between pairs of objects in the knowledge base, wherein each relationship links an object to a related object via a connection specified by name, and wherein said object relationships are implemented using facet values; compute a navigation state including a subset of the objects in the collection in response to interaction with the navigation system, wherein said computation of a navigation state supports path operators specifying a relationship R and an expression E to denote a set of objects related by the relationship R to one or more of the objects in the set specified by E; generate a representation of the navigation state; and compute a set of refinements for the navigation state based on facets of objects related to the subset of objects by at least one of the set of relationships; wherein the instructions for causing the computer to compute the set of refinements for the navigation state include instructions for causing the computer to identify facets describing the objects related to the subset of objects and instructions for causing the computer to execute rules for bounding the computation of the set of refinements, said rules comprising path restriction rules that place a limit on the relationship path expressions that will be included in refinements, said limit specifying an absolute bound on the number of relationship links traversed.