Definition and utilization of project-specific processes is important for effectively conducting industrial information system development. Process tailoring is an approach of achieving processes optimized for the characteristics of a project. However, conventional tailoring techniques such as component-based ones and generator ones lack a way to address the overall consistency or reuse process fragments. In this paper, we propose a technique for establishing process lines, which are sets of common processes in particular problem domains, and process line architectures that incorporate commonality and variability. Process line architectures are used as a basis for deriving process lines from the perspective of overall optimization. The proposed technique includes some extensions to the Software Process Engineering Metamodel for clearly expressing the commonality and variability in the process workflows when modeling the workflows as UML activity diagrams. As a result of applying the proposed technique to hardware/software co-design processes in an embedded system development domain, it is found that the proposed technique is useful for defining consistent and project-specific processes efficiently.