Re: Definitions: caches, history buffers, etc.

Jeffrey Mogul:
>
>Koen writes:
>    The central point of your message, which seems to be that the 1.1
>    draft does not define `cache' in a clear enough way, is better
>    addresed by Roy.
>
>    For the record, I do think you have some point when you say that
>    browser authors can confuse caches with history buffers while
>    reading the 1.1 draft.  But if we start calling history buffers
>    history caches, we will only add to that confusion.
>
>My opinions:
>
>(1) History buffers, whatever you want to call them, are different
>enough from HTTP caches that we need to continue to make this explicit
>in the specification.

Agreed.  I could even imagine that we would want to add a paragraph
about the difference between caches and history mechanisms in Section
13 (Caching) of the 1.1 draft.

>(2) Using the word "cache" to apply to both things seems to be
>a recipe for confusion.  On the principle that confusion is bad,
>and that we ought to be able to agree on almost any term (even
>a made-up word), I suggest that we use the term "history buffer"
>unless someone else has a better suggestion.  In particular,
>let's avoid "history cache."
>
>(3) We need definitions of "cache" and "history buffer" to
>put into the spec.  I'm happy with Roy's definition of cache,
>but in the absence of an equally concise definition of "history
>buffer", I can see how some people could be confused.  So I
>invite people to try to write a definition of "history buffer"
>for use in the spec, and (if necessary) minor tweaks to Roy's
>definition of "cache" to address any possible confusion.

OK, here is my try.

   cache

       A program's local store of HTTP response messages and the
       subsystem that controls its message storage, retrieval, and
       deletion. A cache stores cachable responses in order to reduce
       the response time and network bandwidth consumption on future,
       equivalent HTTP requests. Any client or server may include a
       cache, though a cache cannot be used by a server while it is
       acting as a tunnel.  Though a cache located in a user agent may
       share memory with a history buffer, its message storage,
       retrieval, and deletion subsystem is usually different from the
       control subsystem of a history buffer.

   history buffer

       A user agent's local store containing entities retrieved
       earlier in a session, and the subsystem that controls its
       entity storage, retrieval, and deletion.  User agent history
       mechanisms, such as "Back" buttons and history lists,
       preferably use, but are not limited to using, a history buffer
       to redisplay entities retrieved earlier.  Though a history
       buffer may share memory with a cache, its entity storage,
       retrieval, and deletion subsystem is usually different from the
       control subsystem of a cache.


>-Jeff

Koen.

Received on Tuesday, 9 January 1996 19:17:38 UTC