Hi Paul,

Paul said:
>  Query parameters are NOT representations of resource. Query parameters
>  are part of the address for resources. The representation is the thing
>  that you get when you do a GET or the thing that you PUT or POST.

Didier replies:
Let's add that there is a one to one relationship between a URL and a
resource and a one to one relationship between a resource and a
representation. Therefore there is a one to one relationship between a URL
and a resource. Let's say also that the representation is the manifestation
of a particular URL.
So

URL <-(1,1)-> Resource <- (1,1)-> representation. => URL <- (1,1)->
representation.

It is easy then to see why for people, concretely a resource is what is
referred by a URL and that the resource is the outcome we get when GETting a
resource.

In REST, each URL is a different resource. A resource is unique. What we get
by performing an HTTP GET is a representation of this resource. Therefore we
can say that the representation is some sort of physical (OK, in bits and
bytes or encoded with characters) incarnation of an etherized monad named a
resource. People skip the etherized monad and make the direct connection
Resource <--->  URL (resource being - in that case - what I get with an HTTP
GET). So maybe we can say to make things clear:

a) The resource is an abstract entity representing something on the web. Its
a metaphysical monad, an abstarct thing associated to a concrete thing: the
representation.
b) A resource may be identified by a URI. More particularly its location
represented by a URL and its name by a URN.
c) The outcome of an HTTP GET operation on a particular resource identified
by a particular URI is its representation.

However, a resource has not:
a) several representations
b) several URIs.

cheers
Didier PH Martin


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