So any resource which is addressable on web can be connected from another resource using a hyperlink. In an application based on ROA all the resources should be connected to each other. Connectedness can be achieved in an application if we choose the right representation for a resource. Xml is used to represent any entity in a RPC based architecture. Xml is a default choice because of the fact that it is structured way to represent the entity, hence can be easily understood by computer programs.
As of today the web service returns the data in the form of Xml to make it machine readable while web application represent the data in HTML format in order to make the data human readable. However what we forget is that there's another representation called XHTML which is nothing but HTML which is also a well formed Xml.
So if we can represent all the resources in XHTML computers can parse it as Xml while human can read it on browser as HTML. This also gives us a way to interconnect all the resources in a ROA based application using hyperlinks.
There's no such rule which says that resources should always use XHTML however that would be the preferable since it merges web application and web service and hence make the life easy.
We can still use Xml to represent the resources however in such a case the link to relevant resources should be embedded in the representation of the resource in order to ensure that the whole system is navigable if the user has link to one resource within a system.
This concludes the 5 part series about resource oriented architecture. The next logical step for me would be to design an application using ROA tenets, which involves identifying the right resources, their representation. I might take an enterprise application to do his exercise.
Hope to find some time to do that....