Patent ID: 7774198

Claim:
A computer retrieval system comprising: memory which stores instructions comprising: instructions for receiving a user query in a natural language; instructions for identifying text strings from an associated knowledge base stored in associated memory, each identified text string in the knowledge base containing at least one expression which is matched with at least one expression of the user query, each text string comprising a sequence of words forming a sentence of a document; instructions for refining the user query comprising instructions for representing at least a group of the text strings identified from different text documents as a navigation tree in which each of a plurality of selectable nodes comprises a linguistically coherent expression representative of at least one syntactic unit in at least one of the identified text strings and wherein parent-child relationships between syntactic units in text strings in the group of text strings are determined and used in structuring links between the respective nodes of the navigation tree, whereby in navigating the tree, a user is able to select nodes which refine the query by selecting a first node and selecting a second node which is linked to the first node in the tree, the first and second linguistically coherent expressions of the first and second nodes being representative of syntactic units in a same one of the identified text strings; and instructions for retrieving text documents from the knowledge base related to the refined query; and a processor which executes the instructions.