The design, build and evaluation of an ontology-based knowledge management system prototype tool À À À entitled CMMIoKMS À À À for supporting the consultation and understanding of CMMI for Development (CMMI-DEV) is reported. Ontology-based tools have been proposed for improving such complex cognitive tasks realized by Software Engineering practitioners involved in CMMI implementations. The design of the CMMI-oKMS prototype tool is based on four proprietary ontologies (of things, of systems, of business, and of CMMI models) and built with Prot eg e tool. The result from a pilot empirical test, is reported as being satisfactory À À À compared with the extant reported systems À À À on the metric of perceived value (with statistical signi¯cance) and over usefulness, compatibility, and test score constructs (with practical International 999 Int. J. Soft. Eng. Knowl. Eng. 2013.23:999-1032. Downloaded from www.worldscientific.com by UNIVERSITY OF OTAGO on 03/13/15. For personal use only.signi¯cance), while no gain was found in ease of use. Hence, given the limited number of similar KMS tools reported in the current literature, this research contributes to our body of knowledge in Software Engineering by providing useful design, building and evaluation insights for improving these knowledge support systems.