Query regarding HTTP headers and HTTP response status

Question

I am trying to build a REST service and I have a few questions.

1. When I send Location header is body required?
2. If-modified-since : Can this header value be null or not set to indicate whatever latest version in PUT and DELETE calls?

Answer 1

1. No, the Location header does not require body content. In fact, if the status code of the response is 302 Found or a similar redirect, body content would make no sense.
2. The header If-modified-since is part of the HTTP concept 'Conditional GET'. If it is not set and if not other header that is part of this concept ( If-Match , If-None-Match , If-Unmodified-Since ) is set, the server is supposed to return a representation of the current resource.

In fact, Conditional GET is not a concept about versions but about caching. If the client already knows a representation of the resource that is still up-to-date, it would be redundand for the server to return the same representation again.