I have a resource

  /system/resource

And I wish to ask the system a boolean question about the resource that can't be answered by processing on the client (i.e I can't just GET the resource and look through the actual resource data - it requires some processing on the backend using data not available to the client). eg

  /system/resource/related/otherresourcename

I want this is either return true or false. Does anyone have any best practice examples for this type of interaction?

Possibilities that come to my mind:

• use of HTTP status code, no returned body (smells wrong)

• return plain text string (True, False, 1, 0) - Not sure what string values are appropriate to use, and furthermore this seems to be ignoring the Accept media type and always returning plain text

• come up with a boolean object for each of my support media types and return the appropriate type (a JSON document with a single boolean result, an XML document with a single boolean field). However this seems unwieldy.

I don't particularly want to get into a long discussion about the true meaning of a RESTful system etc - I have used the word REST in the title because it best expresses the general flavour of system I am designing (even if perhaps I am tending more towards RPC over the web rather than true REST). However, if someone has some thoughts on how a true RESTful system avoids this problem entirely I would be happy to hear them.