Refine text about application caches

draft-ietf-httpbis-cache-latest.xml

@@ -1856,10 +1856,20 @@
    This specification does not prohibit the application from taking HTTP caching into
    account; for example, a history mechanism might tell the user that a view
    is stale, or it might honor cache directives (e.g., Cache-Control:
-   no-store). In particular, when an application caches data and does not make this
+   no-store).
+</t>
+<t>
+   However, when an application caches data and does not make this
    apparent to or easily controllable by the user, it is strongly encouraged to
-   honour basic control mechanisms like Cache-Control: no-store, as they
-   indicate the resource's intent regarding caching.
+   define its operation with respect to HTTP cache directives, so as
+   not to surprise authors who expect caching semantics
+   to be honoured. For example, while it might be reasonable to define an
+   application cache "above" HTTP that allows a response containing
+   Cache-Control: no-store to be reused for requests that are directly related
+   to the request that fetched it (such as those created during the same page
+   load), it would likely be surprising and confusing to users and authors if it
+   were allowed to be reused for requests unrelated in any way to the one from
+   which it was obtained.
 </t>
 </section>