19. A method of processing text intervals, comprising: extracting a first proposition from a first text interval; providing a plurality of semantic roles, wherein each role of the plurality of roles defines a different semantic relationship between at least two words; generating a first proposition tree from the first proposition, wherein the first proposition tree comprises at least one node connected to other nodes by at least one edge, wherein each node is respectively associated with at least one word from the first proposition; assigning at least one of the plurality of roles to the at least one edge; determining a first similarity value between the first text interval and a second text interval based on a comparison of the first proposition tree and a second proposition tree corresponding to the second text interval, wherein the second text interval is different from the first text interval and at least one of the first text interval and the second text interval comprises natural language; and selectively outputting, using a processor, the second text interval based the first similarity value.
27. The method of claim 19 , comprising: generating a first bag of nodes from the first proposition tree and a second bag of nodes from the second proposition tree; and determining a second similarity value by matching the first bag of nodes to the second bag of nodes.