Product line engineering (PLE) is an emerging reuse approach, and it has two processes; core asset engineering and application engineering. Various artifacts are produced in PLE, and there is no strong consensus on the key elements of each artifact. Moreover, precise mappings and relationships among the artifacts are yet to define. In order to apply PLE practically and to automate PLE process, elements of artifacts and their relationships should be precisely specified. In this paper, we first present a generic PLE process based on representative PLE approaches. Then, we define meta-models of PLE artifacts, to show how each artifact can be represented at conceptual and physical levels. Finally, we specify an overall traceability map, trace links and mapping relationships. With our foundation of PLE traceability, PLE artifacts such as core assets and instantiated products can be more efficiently and correctly developed. Also, this work paves the way to semi-automate the overall PLE process.