Clarify various usage scenarios for URI templates

Format the one we have better, and also explain how using
both instance data and describing client input is analogous
to common interactive form usage.

Author: handrews

jsonschema-hyperschema.xml

@@ -504,15 +504,40 @@
                         to server-supplied instance data if no user agent data is provided.
                     </t>
                     <t>
-                        The common pattern of resolving a templated path component with
-                        server-supplied instance data while accepting user agent data to build
-                        a query string can be implemented by setting the "hrefSchema" subschemas
-                        for the path template variables to false, while giving the query string
-                        template variables names that do not appear in the instance.  This ensures
-                        that the path variables can only be resolved from the instance, and the
-                        query string variables can only be resolved from user agent data.
+                        To implement the common pattern of resolving a templated path component
+                        with server-supplied instance data while accepting user agent data to build
+                        a query string:
+                        <list style="symbols">
+                            <t>
+                                set the "hrefSchema" subschemas for the path template variables
+                                to false, to disallow user agent input
+                            </t>
+                            <t>
+                                give the query string template variables names that do not appear
+                                in the instance, to prevent resolving them from the instance
+                            </t>
+                        </list>
                         See the "hrefSchema" section for an example of this approach.
                     </t>
+                    <t>
+                        To implement the equivalent of an input form pre-populated with
+                        pre-existing instance data:
+                        <list style="symbols">
+                            <t>
+                                ensure that each variable in the form resolves from the appropriate
+                                field in the instance, which provides the initial value that will
+                                continue to be used if the user agent takes no action to change it
+                            </t>
+                            <t> provide a validation schema for each of those fields in
+                                "hrefSchema", to describe what user agent input may be allowed
+                                to replace it
+                            </t>
+                        </list>
+                        This can be done with variables in any component of the URI template
+                        (path, query string, etc.)  While the word "form" is used here,
+                        JSON Hyper-Schema does not constraint the nature of this interaction, which
+                        may or may not involve rendering an interactive form.
+                    </t>
                 </section>
                 <section title="Manipulating the target resource representation">
                     <t>