Entity Tags

David G. Durand (david@dynamicdiagrams.com)
Thu, 1 Aug 1996 15:52:32 -0700

  I just read through the spec of Entity Tags. They are unique keys
intended to allow comparison of documents to determine cacheability.
So if the Entity tag is the same, the document is byte-for-byte identitical.
If the the Entity tag is "Weak", then it may not be byte-for-byte identical,
if the tags are the same, but the server is saying that it doesn't care,
and caching would still be acceptable. I didn't have a chance to check out
how this affects content-type negotiation, but I got the impression that each
type would have its own entity tag.

   It seems to me that a versioning system provides the right information to
calculate this stuff correctly (and is under obligation to do so), but that
ETags don't solve many of our problems for us (though they do provide a nice
way to check if the "current version" has changed or not).

   I'm not sure that there's much more to this. Anyone with more in-depth
experience and different opinions?

  -- David
David Durand                 dgd@cs.bu.edu| david@dynamicDiagrams.com
Boston University Computer Science        | Dynamic Diagrams
http://www.cs.bu.edu/students/grads/dgd/  | http://dynamicDiagrams.com/