Add general validation principles and examples.

handrews · handrews · commit f28a7f627935 · 2016-11-16T21:20:08.000-08:00
This paritally addresses issue json-schema-org#55 plus concerns raised in the comments of issue json-schema-org#101. I replaced "linearity" with "independence" as I think it is more general and intuitive. The general considerations section has been reorganized to start with the behavior of the empty schema, then explain keyword independence, and finally cover type applicability. In draft 04, the wording obscured the connection between keyword independence and container/child independence. I thought I needed this primitive type vs child validation section even with the rewritten keywords, but going over it now based on feedback, I agree that it is superfluous. The list of non-independent keywords has been updated to include minimum/maximum and their "exclusive" booleans.
diff --git a/jsonschema-validation.xml b/jsonschema-validation.xml
@@ -156,54 +156,68 @@
 
         <section title="General validation considerations">
 
-            <section title="Keywords and instance primitive types">
+            <section title="Constraints and missing keywords">
                 <t>
-                    Most validation keywords only limit the range of values within a certain primitive type.
-                    When the primitive type of the instance is not of the type targeted by the keyword, the
-                    validation succeeds.
+                    Each JSON Schema validation keyword adds constraints that
+                    an instance must satisfy in order to successfully validate.
                 </t>
                 <t>
-                    For example, the "maxLength" keyword will only restrict certain strings (that are too long) from being valid.
-                    If the instance is a number, boolean, null, array, or object, the keyword passes validation.
-                </t>
+                    Validation keywords that are missing never restrict validation.
+                    In some cases, this no-op behavior is identical to a keyword that
+                    exists with certain values, and these values are noted where relevant.
+                </t>
+                <figure>
+                    <preamble>
+                        From this principle, it follows that all JSON values
+                        successfully validate against the empty schema:
+                    </preamble>
+                    <artwork>
+<![CDATA[
+{}
+]]>
+                    </artwork>
+                </figure>
+                <figure>
+                    <preamble>
+                        Similarly, it follows that no JSON value successfully
+                        validates against the empty schema's negation:
+                    </preamble>
+                    <artwork>
+<![CDATA[
+{
+    "not": {}
+}
+]]>
+                    </artwork>
+                </figure>
             </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>
+            <section title="Keyword independence">
                 <t>
-                    For objects, primitive type validation consists of validating restrictions on the presence
-                    or absence of property names.
+                    Validation keywords typically operate independently, without
+                    affecting each other's outcomes.
                 </t>
-            </section>
-
-            <section title="Missing keywords">
                 <t>
-                    Validation keywords that are missing never restrict validation.
-                    In some cases, this no-op behavior is identical to a keyword that exists with certain values,
-                    and these values are noted where known.
+                    For schema author convenience, there are some exceptions:
+                    <list>
+	                    <t>"additionalProperties", whose behavior is defined in terms of "properties" and "patternProperties"</t>
+                        <t>"additionalItems", whose behavior is defined in terms of "items"</t>
+                        <t>"minimum" and "maximum", whose behaviors are modified by "exclusiveMinimum" and "exclusiveMaximum", respectively</t>
+                    </list>
                 </t>
             </section>
 
-            <section title="Linearity">
-                <!-- I call this "linear" in the same manner e.g. waves are linear, they don't interact with each other -->
+            <section title="Keywords and instance primitive types">
                 <t>
-                    Validation keywords typically operate independent of each other, without affecting each other.
+                    Most validation keywords only limit the range of values within a certain primitive type.
+                    When the primitive type of the instance is not of the type targeted by the keyword, the
+                    validation succeeds.
                 </t>
                 <t>
-                    For author convienence, there are some exceptions:
-                    <list>
-	                     <t>"additionalProperties", whose behavior is defined in terms of "properties" and "patternProperties"; and</t>
-                        <t>"additionalItems", whose behavior is defined in terms of "items"</t>
-                    </list>
+                    For example, the "maxLength" keyword will only restrict certain strings (that are too long) from being valid.
+                    If the instance is a number, boolean, null, array, or object, the keyword passes validation.
                 </t>
             </section>
-
         </section>
 
         <section title="Validation keywords">
@@ -505,7 +519,7 @@
                 </t>
                 <t>
                     For all such properties, child validation succeeds if the child instance
-                    validates agains the "additionalProperties" schema.
+                    validates against the "additionalProperties" schema.
                 </t>
             </section>
 
@@ -663,7 +677,7 @@
                 <t>
                     Both of these keywords can be used to decorate a user interface with
                     information about the data produced by this user interface. A title will
-                    preferrably be short, whereas a description will provide explanation about
+                    preferably be short, whereas a description will provide explanation about
                     the purpose of the instance described by this schema.
                 </t>
                 <t>
@@ -812,11 +826,11 @@
 
         <section title="Security considerations">
             <t>
-                JSON Schema validation defines a vocabulary for JSON Schema core and conserns all the security considerations listed there.
+                JSON Schema validation defines a vocabulary for JSON Schema core and concerns all the security considerations listed there.
             </t>
             <t>
                 JSON Schema validation allows the use of Regular Expressions, which have numerous different (often incompatible) implementations.
-                Some implementations allow the embedding of arbritrary code, which is outside the scope of JSON Schema and MUST NOT be permitted.
+                Some implementations allow the embedding of arbitrary code, which is outside the scope of JSON Schema and MUST NOT be permitted.
                 Regular expressions can often also be crafted to be extremely expensive to compute (with so-called "catastrophic backtracking"),
                 resulting in a denial-of-service attack.
             </t>
