Should the Purpose of Conversation be Pre-Established?

In response to my recent post on Resource Oriented Architecture (ROA), Abhijit Nadgouda made the following comment:

Not sure if this meant that the capability was a surprise to the client. If the client did not know of the capability, why did the client engage with the resource? Shouldn't the purpose of conversation be pre-established? Should the client expect any capability from the resource?

Just to clue you in, I was talking about the absence of a need for a client to know the particulars for the resource the client is interacting with. So long as the resource understands the request to represent itself, to make a state transition, and to eventually destroy itself, the client can accomplish its goal.

Now, when the client identifies and locates the resource, it is most natural for the client to expect to receive the representation of that resource. To use the example from my original post, if I, as a client, am looking for a tennis court where I could play with my friends, upon identifying and locating the potential court, I'd like to see its representation.

At that point, the identified tennis court will ship its representation to me. This representation will then be rendered in my browser. By examining the representation I've just received, I should be able to get a better picture about the resource's capability.

Now, Abhijit's question is: is this capability a surprise to me, the client? Well, hard to say, isn't it? I mean, it all depends on what I, as a client, was expecting when engaging in the conversation with the resource.

If, for instance, I was expecting the resource to offer shower facilities and it didn't, then yes, maybe I'd be surprised. But then again maybe not, because many of the public tennis courts in my city do not offer any amenities.

The Web Is About Exploratory Behavior

Another interesting question is this:

If the client did not know of the capability, why did the client engage with the resource?

It's called exploration. And web is all about exploring. Poking around. Does this tennis court have a wall to bounce the ball off of, or not? I don't know, let's explore and find out.

Shouldn't the Purpose of Conversation be Pre-Established?

Why enforce such a constraint? The web is also about freedom. Let me start by an informal chat, and see where it takes us. There's no need to impose an authoritarian, military type of a rigid conversation that mustn't deviate from the very narrow 'norm'.

Should the Client Expect any Capability from the Resource?

Yes, and we've covered that expectation in very many details already. To reiterate, a web client invariably expects any resource on the web to be capable of representing itself, of making the transition of its state, and of destroying itself.