does the protocol require certain media types?

[lisp]

the requirement expressed in section 5, graph management operations, about media type should be improved.
it now reads

If the Accept header is not provided with a GET request, the server MUST return one of RDF XML, Turtle, or N-Triples.

there are several issues

• is "*/*" to be treated the same as when there is no accept header at all?
• if some media type is specified which the service does not support, should it respond with a "406 Not Acceptable" or should it respond with a type which it does support?
• if the response is a 406, is there a set of representations which must be supplied in the response as the list of acceptable media types?

[afs]

@lisp ,

The way I see the graph store protocol (GSP) is that it is not a special use of HTTP; it describes how to use the HTTP protocol.

GSP discusses naming and it does define indirect naming (?default, ?graph=) but otherwise any HTTP client can be used.

There is no requirement that the HTTP client software is aware of GSP.

is "/" to be treated the same as when there is no accept header at all?

Technically, no. This is by definition of HTTP. It appears to be very common practice to treat no Accept as the same as */*. curl, for example, defaults to having Accept: */*.

if some media type is specified which the service does not support, should it respond with a "406 Not Acceptable" or should it
respond with a type which it does support?

Either - this is by definition of HTTP. Accept is not a strict condition, it is a preference. Returning any media type is allowed by HTTP. Sender and service are equal partners in the exchange.

https://httpwg.org/specs/rfc9110.html#status.406
"and the server is unwilling to supply a default representation."

if the response is a 406, is there a set of representations which must be supplied in the response as the list of acceptable media types?

1. SPARQL Service Description sd:resultFormat
2. https://httpwg.org/specs/rfc9110.html#status.406 does not define such a thing that I can see.

And the client can use HEAD with a quality value q=.
https://httpwg.org/specs/rfc9110.html#HEAD
"HEAD is used to obtain metadata about the selected representation without transferring its representation data, often for the sake of testing hypertext links or finding recent modifications."

[lisp]

The way I see the graph store protocol (GSP) is that it is not a special use of HTTP; it describes how to use the HTTP protocol.

as an aspect of which - actually either, as i do not understand what difference the distinction would make to the recommendation's reader, the recommendation text does help the reader to understand how to interact with the service.

There is no requirement that the HTTP client software is aware of GSP.

if the client intended to follow gsp, they would have to be.

.... It appears to be very common practice to treat no Accept as the same as */*. curl, for example, defaults to having Accept: */*.

the recommendation could provide for clarity beyond common practice.

...

if the response is a 406, is there a set of representations which must be supplied in the response as the list of acceptable media types?

1. SPARQL Service Description sd:resultFormat
2. https://httpwg.org/specs/rfc9110.html#status.406 does not define such a thing that I can see.

the copy which i found at that location did not define the list, but it did describe it

• https://www.rfc-editor.org/rfc/rfc9110.html#name-406-not-acceptable

the protocol document had two relevant passages :

• https://datatracker.ietf.org/doc/html/rfc7231#section-3.4.2
• https://datatracker.ietf.org/doc/html/rfc7231#section-6.5.6