Despite the widespread adoption of web services, several obstacles still hinder their smooth automatic composition. First, techniques that exploit semantic information during web services discovery are still lagging behind despite multiple initiatives like OWL-S. Second, the context in which web services evolve is, to a certain extent, ignored. This prevents deploying adaptable web services. In this paper, we propose a semantic- and context-based approach for web services composition. By semantics, we mean the capacity of web services, which are engaged in interactions, to understand what these interactions are about and how to carry out these interactions. By context, we mean the capacity of web services to assess their current capabilities and ongoing commitments before these services participate in any composition.