[Feature] Discovery process [Webinos proposal] UA searches for networked services at API invocation.A successCallback is issued for each service found. Timer for how long search process lasts could be set. Pending search process can be canceled [Opera/CableLabs proposal] UA searches for networked services (the timing of which is at the discretion of the UA) in the local network and on user visited web sites and maintains a list of currently available services. [Google Web Intents] A web application wanting to use a service calls a simple API stating the requested Action and Type. An iframe allows the user to select one of the registered services for this Action and Type. [Google Web Introducer] 
A web application wanting to use a service calls a simple API stating the requested intent. An iframe or a new window allows the user to select one of the registered services for this intent.