Clarify why processing @context is useful for JSON-based processors.

index.html

@@ -1823,8 +1823,8 @@ <h3>Lifecycle Details</h3>
         </ol>
 
         <p class="note">
-The order of the steps above is not fixed, and some steps might be taken 
-more than once. Such step-recurrence may be immediate or at any later 
+The order of the steps above is not fixed, and some steps might be taken
+more than once. Such step-recurrence may be immediate or at any later
 point in the sequence as performed.
         </p>
 
@@ -2105,20 +2105,17 @@ <h3>Extensibility</h3>
           <h4>Semantic Interoperability</h4>
 
           <p>
-This specification endeavors to enable both the JSON and JSON-LD syntaxes to
-be semantically compatible with one another without the JSON implementations
-needing to process the documents as JSON-LD. To achieve this, the
-specification imposes the following additional restrictions on both syntaxes:
+This specification ensures that "plain" JSON and JSON-LD syntaxes are
+semantically compatible without requiring JSON implementations to use a
+JSON-LD processor. To achieve this, the specification imposes the following
+additional requirements on both syntaxes:
           </p>
 
           <ul>
             <li>
 JSON-based processors MUST process the <code>@context</code> <a>property</a>,
 ensuring the expected values exist in the expected order for the
-<a>credential</a> type being processed. It is advised that the expected order
-of values of the <code>@context</code> <a>property</a> should be defined by
-at least a human-readable extension specification and preferably by a
-machine-readable specification as well.
+<a>credential</a> type being processed.
             </li>
             <li>
 JSON-LD-based processors MUST produce an error when a JSON-LD context
@@ -2131,6 +2128,25 @@ <h4>Semantic Interoperability</h4>
             </li>
           </ul>
 
+          <p>
+A human-readable document describing the expected order of values for the
+<code>@context</code> <a>property</a> is expected to be published by any
+implementer seeking interoperability. A machine-readable description
+(i.e., a normal JSON-LD Context document) is expected to be published
+at the URL specified in the <code>@context</code> <a>property</a> by
+JSON-LD implementers seeking interoperability.
+          </p>
+
+          <p>
+The requirements above guarantee semantic interoperability between JSON and
+JSON-LD for terms defined by the <code>@context</code> mechanism. While JSON-LD
+processors will use the specific mechanism provided and can verify that all
+terms are correctly specified, JSON-based processors implicitly accept the same
+set of terms without testing that they are correct. In other words, the context
+in which the data exchange happens is explicitly stated for both JSON and
+JSON-LD by using the same mechanism. With respect to JSON-based processors,
+this is achieved in a lightweight manner, without having to use JSON-LD
+processing libraries.
         </section>
       </section>