This thesis presents a complete set of user requirements and high-level architecture for [a] product lifecycle management (PLM) system for small and medium-sized enterprises (SMEs). Engineering activities such as engineering change management (ECM) and product data management (PDM) are emphasized. The system is designed to be developed in [an] open source environment. Therefore the system is called Open Product Lifecycle Management (OPLM) system. The thesis begins with a presentation of the motivation for the work and description of products and literature in the areas of PLM, SME and open source. An industry survey is conducted to elicit requirements of OPLM. Engineering change management (ECM) process is described and a modified framework for ECM in OPLM is presented. The proposed model is expected to make ECM faster, reusable and accurate. Four OPLM subsystems, namely, product data management, engineering change management, process management and business intelligence are defined. For each of the subsystems, subsystem components are identified and defined.