Futher clarify primitive vs child validation.

A lot of the most confusing language around the "additional" keywords
can be removed if we consider keywords strictly with respect to either
the instance's primitive type or against child instances.

Describing {"additionalItems": false} as failing child validation of
elements beyond the length of "items" is more straightforward and
has the same effect as the more convoluted reasoning about length.

Author: handrews

Diff for: jsonschema-validation.xml

@@ -168,6 +168,20 @@
                 </t>
             </section>
 
+            <section title="Validation of primitive types and child values">
+                <t>
+                    Two of the primitive types, array and object, allow for child values.  The validation of
+                    the primitive type is considered separately from the validation of child instances.
+                </t>
+                <t>
+                    For arrays, primitive type validation consists of validating restrictions on length.
+                </t>
+                <t>
+                    For objects, primitive type validation consists of validating restrictions on the presence
+                    or absence of property names.
+                </t>
+            </section>
+
             <section title="Missing keywords">
                 <t>
                     Validation keywords that are missing never restrict validation.
@@ -306,7 +320,8 @@
                     If absent, it can be considered present with an empty schema.
                 </t>
                 <t>
-                    Validation of this keyword against the instance always succeeds.
+                    This keyword controls child instance validation.  Validation of the
+                    primitive instance type against this keyword always succeeds.
                 </t>
                 <t>
                     If "items" is a schema, child validation succeeds if all elements
@@ -328,29 +343,13 @@
                     If absent, it can be considered present with an empty schema.
                 </t>
                 <t>
-                    If "additionalItems" is true or a schema, or if "items"
-                    is absent or a single schema, or if the instance is not
-                    an array, then validation of the instance always succeeds.
-                </t>
-                <t>
-                    If "additionalItems" is false, and "items" is an array
-                    of schemas, validation of the instance succeeds if
-                    the size of the instance is less than, or equal to,
-                    the size of "items".
-                </t>
-                <t>
-                    Child validation with respect to "additionalItems" only applies
-                    when "items" is an array of schemas, and only applies to
-                    instance elements at positions greater than the size of "items".
-                </t>
-                <t>
-                    If "additionalItems" is true, child validation always succeeds.
+                    This keyword controls child instance validation.  Validation of the
+                    primitive instance type against this keyword always succeeds.
                 </t>
                 <t>
-                    If "additionalItems" is a schema, child validation succeeds
-                    if all instance elements at positions greater than the size
-                    of "items" successfully validate against the "additionalItems"
-                    schema.
+                    If "items" is an array of schemas, child validation succeeds
+                    if every instance element at a position greater than the size
+                    of "items" validates against "additionalItems".
                 </t>
             </section>
 
@@ -444,7 +443,8 @@
                     If absent, it can be considered the same as an empty object.
                 </t>
                 <t>
-                    Validation of this keyword against the instance always succeeds.
+                    This keyword controls child instance validation.  Validation of the
+                    primitive instance type against this keyword always succeeds.
                 </t>
                 <t>
                     Child validation succeeds if, for each name that appears in both
@@ -464,7 +464,8 @@
                     If absent, it can be considered the same as an empty object.
                 </t>
                 <t>
-                    Validaton of this keyword against the instance always succeeds.
+                    This keyword controls child instance validation.  Validation of the
+                    primitive instance type against this keyword always succeeds.
                 </t>
                 <t>
                     Child validation succeeds if, for each instance name that matches any
@@ -484,27 +485,17 @@
                     an empty schema as a value.
                 </t>
                 <t>
-                    If "additionalProperties" is either true or a schema, or if the instance
-                    is not an object, validation against the instance always succeeds.
-                </t>
-                <t>
-                    If "additionalProperties" is false and the instance is an object,
-                    validation against the instance succeeds only if all properties names
-                    in the instance match a name specified in "properties" and/or match
-                    at least one regular expression specified in "patternProperties".
+                    This keyword controls child instance validation.  Validation of the
+                    primitive instance type against this keyword always succeeds.
                 </t>
                 <t>
                     Child validation with "additionalProperties" applies only to the child
-                    valuse of instance names that do not match any names in "properties",
+                    values of instance names that do not match any names in "properties",
                     and do not match any regular expression in "patternProperties".
                 </t>
                 <t>
-                    If "additionalProperties" is true, child validation always succeeds.
-                </t>
-                <t>
-                    If "additionalProperties" is a schema, child validation succeeds if
-                    all child instances to which "additionalProperties" applies validate
-                    against that schema.
+                    For all such properties, child validation succeeds if the child instance
+                    validates agains the "additionalProperties" schema.
                 </t>
             </section>