[answer provded by Ken Amann of CIMdata ] PLM addresses the complete product definition -- mechanical, electronic, and software. Software modules and releases are considered part of the product definition and configuration, and are managed as such. Generally, development of software is handled by CASE tools, e.g., Clear Case. Once a build is completed and approved, the associated files and information are uploaded into the managing PLM system and the appropriate links to the mechanical and electronic component configuration are established. Changes to software (and the associated electronic and mechanical equipment) under configuration control must be approved before being incorporated. This enables designers, developers, manufacturing, and service personnel to access the product information and see the complete definition at any point in time. It also ensures that they work with (and don’t violate) the correct configuration of the version upon which they are working