In Chap. 5, we have presented a description language that not only captures the
complexity of architectural domains and their relations, but also enables the integration
at the appropriate level of abstraction of already existing partial architecture
models. However, the value of architecture models increases significantly if they can
also be used to support the decision-making process. In this chapter we argue that
whenever a change in the enterprise architecture is needed, model-based analysis
plays a central role. Therefore, we present a number of techniques that help architects
and stakeholders to compare alternative designs and, hence, take well-informed
design decisions when making trade-offs between aspects like cost, quality, and
performance and to be able to study the impact of a change to the design.