Software maintenance function suffers from a scarcity of management models that would facilitate its evaluation, management and continuous improvement. This paper is part of a series of papers that presents a Software Maintenance Capability Maturity Model (SM^CMM). The contributions of this specific paper are: 1) to describe the key references of software maintenance; 2) to present the model update process conducted during 2003; and 3) to present, for the first time, the updated architecture of the model.