Changeset 2390

Timestamp:

14/09/13 05:30:06 (7 years ago)

Author:

fielding@…

Message:

remind folks why weak or strong comparison is used; addresses #495

Location:

draft-ietf-httpbis/latest

Files:

• p4-conditional.html (modified) (3 diffs)
• p4-conditional.xml (modified) (3 diffs)

draft-ietf-httpbis/latest/p4-conditional.html

@@ -704 +704 @@
       </p>
       <p id="rfc.section.2.1.p.9">A "use" of a validator occurs when either a client generates a request and includes the validator in a precondition or when
-         a server compares two validators. Weak validators are only usable in contexts that do not depend on exact equality of the
-         representation data. Strong validators are usable and preferred for all conditional requests, including cache validation,
-         partial content ranges, and "lost update" avoidance.
+         a server compares two validators. Weak validators are only usable for use cases that do not depend on exact equality of the
+         representation data, such as cache validation, or for limiting the scope of web traversals to recently changed representations.
+         Strong validators are usable and preferred for all conditional requests, including cache validation, partial content ranges,
+         and "lost update" avoidance.
       </p>
       <div id="rfc.iref.l.1"></div>
@@ -941 +942 @@
          the target resource that has an entity-tag matching a member of the list of entity-tags provided in the field-value.
       </p>
-      <p id="rfc.section.3.1.p.2">A recipient <em class="bcp14">MUST</em> use the strong comparison function when comparing entity-tags for If-Match (<a href="#entity.tag.comparison" title="Comparison">Section&nbsp;2.3.2</a>).
+      <p id="rfc.section.3.1.p.2">A recipient <em class="bcp14">MUST</em> use the strong comparison function when comparing entity-tags for If-Match (<a href="#entity.tag.comparison" title="Comparison">Section&nbsp;2.3.2</a>), since the client intends this precondition to prevent the method from being applied if there have been any changes to the
+         representation data.
       </p>
       <div id="rfc.figure.u.8"></div><pre class="inline"><span id="rfc.iref.g.7"></span>  <a href="#header.if-match" class="smpl">If-Match</a> = "*" / 1#<a href="#header.etag" class="smpl">entity-tag</a>
@@ -968 +970 @@
          target resource that has an entity-tag matching a member of the list of entity-tags provided in the field-value.
       </p>
-      <p id="rfc.section.3.2.p.2">A recipient <em class="bcp14">MUST</em> use the weak comparison function when comparing entity-tags for If-None-Match (<a href="#entity.tag.comparison" title="Comparison">Section&nbsp;2.3.2</a>).
+      <p id="rfc.section.3.2.p.2">A recipient <em class="bcp14">MUST</em> use the weak comparison function when comparing entity-tags for If-None-Match (<a href="#entity.tag.comparison" title="Comparison">Section&nbsp;2.3.2</a>), since weak entity-tags can be used for cache validation even if there have been changes to the representation data.
       </p>
       <div id="rfc.figure.u.10"></div><pre class="inline"><span id="rfc.iref.g.8"></span>  <a href="#header.if-none-match" class="smpl">If-None-Match</a> = "*" / 1#<a href="#header.etag" class="smpl">entity-tag</a>

draft-ietf-httpbis/latest/p4-conditional.xml

@@ -287 +287 @@
    and includes the validator in a precondition or when a server
    compares two validators.
-   Weak validators are only usable in contexts that do not depend on exact
-   equality of the representation data.
+   Weak validators are only usable for use cases that do not depend on exact
+   equality of the representation data, such as cache validation, or for
+   limiting the scope of web traversals to recently changed representations.
    Strong validators are usable and preferred for all conditional requests,
    including cache validation, partial content ranges, and "lost update"
@@ -677 +678 @@
 <t>
    A recipient &MUST; use the strong comparison function when comparing
-   entity-tags for If-Match (<xref target="entity.tag.comparison"/>).
+   entity-tags for If-Match (<xref target="entity.tag.comparison"/>), since
+   the client intends this precondition to prevent the method from being
+   applied if there have been any changes to the representation data.
 </t>
 <figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="If-Match"/>
@@ -736 +739 @@
 <t>
    A recipient &MUST; use the weak comparison function when comparing
-   entity-tags for If-None-Match (<xref target="entity.tag.comparison"/>).
+   entity-tags for If-None-Match (<xref target="entity.tag.comparison"/>),
+   since weak entity-tags can be used for cache validation even if there have
+   been changes to the representation data.
 </t>
 <figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="If-None-Match"/>