In a distributed computing environment, a service advertisement may include information for a client to access a particular service. A service may publish the service advertisement in a space which stores documents such as eXtensible Markup Language (XML) documents. The advertisement may include a Uniform Resource Identifier (URI) and an XML schema for the service that specifies XML messages which are usable to invoke functions of the service. A client may access the space and read the advertisement to construct a gate for access to the service. The client may send a first XML message to the service at the URI, wherein the first XML message is specified in the XML schema, to invoke one or more functions of the service. The service may send a second message specified in the XML schema (e.g., a message including the results of the invoked function(s)) to the client.