How to specify request headers?

[mlagally]

There's a normative requirement to specify request headers as part of a form.

Every form in a WoT Thing Description MUST accurately describe requests (including request headers, if present) accepted by the Thing in an interaction.

How can that be done?

[egekorkan]

This is actually an important question and further examples can help clarifying this.

So this done via the Protocol Bindings with HTTP being available in the TD spec. For example, htv:methodName can be used to indicate the method to be used in HTTP. Method Name is a request header but there are of course other headers.

As explained in https://w3c.github.io/wot-thing-description/#http-binding-assertions , one solution is to use the HTTP in RDF at https://www.w3.org/TR/HTTP-in-RDF10/ to describe such request headers.

In a TD form, you can have:

"htv:headers":
[
    {
    "htv:fieldName": "Accept",
    "htv:fieldValue": "application/json"
    },

Which means that the Consumer needs to supply an Accept header with value of "application/json" in the request.

In case you are looking for a more generally-applicable answer, I would say that this would be done via context extensions. Please see https://w3c.github.io/wot-thing-description/#sec-context-extensions for more information about this mechanism of the TD (of JSON-LD to be specific).

Note: This assertion was in the 1.0 version as well. Please see https://www.w3.org/TR/wot-thing-description/#protocol-bindings

[mlagally]

@egekorkan
Thanks very much for this explanation, which brings a lot of clarity.
2 questions remain:

• the prefix in the TD spec is htv: whereas in the RDF document it is http: Why?
• the type headers is not in the RDF spec- which headers type do we mean?

[egekorkan]

My pleasure in answering them. For the further questions:

• The prefix is up to the user and if you expand a JSON-LD document, it disappears. When we included this "HTTP in RDF" ontology in the TD ontology, we have used the htv prefix (see https://www.w3.org/2022/wot/td/v1.1). The reason why can be followed in this issue: Using "http" as a term is strange #443 . In short, developers can confuse http:myTerm with http://myterm.
• The headers are available in the RDF spec at https://www.w3.org/TR/HTTP-in-RDF10/#headersProperty . You can also look at https://www.w3.org/2011/http# and find headers

[sebastiankb]

from today's TD call, the group like to close this issue

@mlagally please check if this is ok for you

[egekorkan]

Call of 05.04:

• This was a question, not a bug of the spec. Closing.