  Web Services form a new, emerging paradigm to handle distributed access to
resources over the Internet. There are platform independent standards (SOAP,
WSDL), which make the developers? task considerably easier. This article
discusses how web services could be used in the context of the Virtual
Observatory. We envisage a multi-layer architecture, with interoperating
services. A well-designed lower layer consisting of simple, standard services
implemented by most data providers will go a long way towards establishing a
modular architecture. More complex applications can be built upon this core
layer. We present two prototype applications, the SdssCutout and the SkyQuery
as examples of this layered architecture.
