Service-oriented architectures - and particularly the Web service technologies that enable them, such as WSDL (Web Services Description Language) and SOAP - are widely acknowledged for their potential to revolutionize computing. However, existing SOAs will prove difficult to scale without a proper degree of automation. SOAs' success depends on resolving fundamental challenges that existing SOA technologies don't sufficiently address: search, integration, and mediation. Extending service-oriented architectures with semantics can help create service-centric information systems that better adapt to changes throughout software systems' lifetime.