Web services technologies are advancing fast and being extensively
deployed in many di?erent application environments. Web services based
on the eXt- sible Markup Language (XML), the Simple Object Access
Protocol (SOAP), andrelatedstandards,
anddeployedinService-OrientedArchitectures(SOAs) are the key to
Web-based interoperability for applications within and across
organizations. Furthermore, they are making it possible to deploy appli-
tions that can be directly used by people, and thus making the Web a
rich and powerful social interaction medium. The term Web 2.0 has been
coined to embrace all those new collaborative applications and to
indicate a new, "social" approach to generating and distributing Web
content, characterized by open communication, decentralization of
authority, and freedom to share and reuse. For Web services technologies
to hold their promise, it is crucial that - curity of services and their
interactions with users be assured. Con?dentiality, integrity,
availability, anddigitalidentitymanagementareallrequired.People need to
be assured that their interactions with services over the Web are kept
con?dential and the privacy of their personal information is preserved.
People need to be sure that information they use for looking up and
selecting s-
vicesiscorrectanditsintegrityisassured.Peoplewantservicestobeavailable
when needed. They also require interactions to be convenient and person-
ized, in addition to being private. Addressing these requirements,
especially when dealing with open distributed applications, is a
formidable challenge.
