WSOL (Web Service Offerings Language) is an XML (Extensible Markup Language) notation compatible with the WSDL (Web Services Description Language) standard. While WSDL is used for describing operations provided by Web Services, WSOL enables formal specification of multiple classes of service for one Web Service. A service offering is a formal representation of one class of service for a Web Service. As classes of service for Web Services are determined by combinations of various constraints, WSOL enables formal specification of functional constraints, some QoS (a.k.a., non-functional) constraints, simple access rights (for differentiation of service), price, and relationships with other service offerings of the same Web Service. Describing a Web Service in WSOL, in addition to WSDL, enables selection of a more appropriate Web Service and service offering for particular circumstances. Further, it supports dynamic adaptation and manag! ement of Web Service compositions using manipulation of service offerings.