Our two working groups began by considering first what was meant by the idea of a mental model in the domain of software development, gradually transitioning to micro-architecture issues. We then developed two examples, a sort abstraction and a heapsort implementation, exploring the micro-architecture issues of composibility, local certifiability and performance, and mental model issues of how we think about and represent implementations. After a comparison of mental model and micro-architecture issues and the development of an agenda for the remainder of the workshop, we invited an envoy from the Systematic OO Reuse group in order to explore and compare different approaches to software reuse. We conclude our working group report with a brief catalog of techniques for generalizing components and developing good mental models.