This book originates from a workshop organised by ESPRIT project 20 477, ARES in Las Palmas de Gran Canaria, Spain, February 1998. ARES is an acronym for Architectural Reasoning for Embedded Systems. Within this project we investigate techniques to deal with problems of software architecture of families of embedded systems. It is the second workshop organised by this project. Its predecessor was held in Las Navas de Marques, Spain, November 1996. The proceedings of the first workshop are only available in electronic format at “http: //www.dit.upm.es/ ares/”. The second workshop succeeded, even more than the first one, in gathering many of the most prominent people working in the area of software architecture for product families or product lines. This second workshop consisted of six sessions. The first session was meant to report the ARES results, according to the topics of the next five sessions. The remaining sessions dealt with different aspects of software architecture, focussed on applications for product families or product lines. Because there will be a separate book covering all ARES results, the first session is not included in this book. The workshop was chaired by Henk Obbink from Philips Research and Paul Clements from the Software Engineering Institute at Carnegie Mellon University. They prepared and presented an overall conclusion at the end of the workshop. This conclusion was used in the introduction to this book.