An execution view is an important asset for developing large and complex systems. An execution view helps practitioners to describe, analyze, and communicate what a software system does at runtime and how it does it. In this paper, we present an approach to define and document viewpoints that guide the construction and use of execution views for an existing large and complex software-intensive system. This approach includes the elicitation of the organization's requirements for execution views, the initial definition and validation of a set of execution viewpoints, and the documentation of the execution viewpoints. The validation and application of the approach have helped us to produce mature viewpoints that are being used to support the c...