PT Journal AU Cimiano, P Haase, P Heizmann, J Mantel, M Studer, R TI Towards Portable Natural Language Interfaces to Knowledge Bases - The Case of the ORAKEL System - SO Data & knowledge engineering PY 2008 BP 325 EP 354 VL 65 IS 2 DI 10.1016/j.datak.2007.10.007 LA english ER