Service-Oriented Architectures (SOAs) are fundamentally changing the way in which we conceptualize and design business applications. An SOA-based application typically composes various distributed functions, including some possibly provided by external parties such as independent businesses. The key advantage of SOAs is the resulting dynamism, since the composed parts can be readily swapped out in favor of others of like functionality. SOA environments thus reflect the dynamism of human socioeconomic environments where businesses interact, collaborate, and expose services to each other in order to jointly create value. This paper presents a multiagent model for Web services and catalogs architectural styles that are key for SOA applications. It conceptually evaluates the styles by showing the kinds of service usages and the resulting dynamic interactions that they enable.