From e94c16fd0ddfb9b4bd67778b4373d0fa40b9d220 Mon Sep 17 00:00:00 2001
From: Alexander Stein <alexander.stein@nist.gov>
Date: Thu, 28 Jul 2022 13:13:38 -0400
Subject: [PATCH] Implement default values for flags and fields. (#220)

During pairing on usnistgov/OSCAL#1160, we determined there will be a
lot of utility to have default values when enhancing the draft version
of the Rules Model. This PR implements that functionality in the Metaschema
core syntax defined in the XSD.

Co-authored-by: David Waltermire <david.waltermire@nist.gov>
---
 schema/xml/metaschema.xsd | 22 +++++++++++++++-------
 1 file changed, 15 insertions(+), 7 deletions(-)

diff --git a/schema/xml/metaschema.xsd b/schema/xml/metaschema.xsd
index 75ea0514..23683982 100644
--- a/schema/xml/metaschema.xsd
+++ b/schema/xml/metaschema.xsd
@@ -264,7 +264,7 @@
       <xs:element name="remarks" type="RemarksType" minOccurs="0"/>
       <xs:element name="example" type="ExampleType" minOccurs="0" maxOccurs="unbounded"/>
     </xs:sequence>
-    <xs:attribute name="as-type" type="FieldDatatypesType" default="string"/>
+    <xs:attributeGroup ref="FieldValueAttributeGroup"/>
     <xs:attribute name="collapsible" type="YesNoType" default="no"/>
     <xs:attribute name="name" use="required" type="ModelNameType"/>
     <xs:attribute name="scope" type="ScopeType" default="global"/>
@@ -286,8 +286,7 @@
       <xs:element name="example" type="ExampleType" minOccurs="0" maxOccurs="unbounded"/>
     </xs:sequence>
     <xs:attribute name="name" use="required" type="ModelNameType"/>
-    <!-- datatype should default to 'string' -->
-    <xs:attribute name="as-type" type="SimpleDatatypesType" default="string"/>
+    <xs:attributeGroup ref="FlagValueAttributeGroup"/>
     <xs:attribute name="scope" type="ScopeType" default="global"/>
     <xs:attributeGroup ref="DeprecationAttributeGroup"/>
   </xs:complexType>
@@ -318,7 +317,6 @@
     <xs:attributeGroup ref="DeprecationAttributeGroup"/>
   </xs:complexType>
 
-
   <xs:complexType name="InlineFieldDefinitionType">
     <xs:annotation>
       <xs:documentation>In JSON, an object with a nominal string value (potentially with internal
@@ -339,7 +337,7 @@
       <xs:element name="remarks" type="RemarksType" minOccurs="0"/>
       <xs:element name="example" type="ExampleType" minOccurs="0" maxOccurs="unbounded"/>
     </xs:sequence>
-    <xs:attribute name="as-type" type="FieldDatatypesType" default="string"/>
+    <xs:attributeGroup ref="FieldValueAttributeGroup"/>
     <xs:attribute name="collapsible" type="YesNoType" default="no"/>
     <xs:attributeGroup ref="CardinalitySpecificationGroup"/>
     <xs:attribute name="name" use="required" type="ModelNameType"/>
@@ -363,8 +361,7 @@
       <xs:element name="example" type="ExampleType" minOccurs="0" maxOccurs="unbounded"/>
     </xs:sequence>
     <xs:attribute name="name" use="required" type="ModelNameType"/>
-    <!-- datatype should default to 'string' -->
-    <xs:attribute name="as-type" type="SimpleDatatypesType" default="string"/>
+    <xs:attributeGroup ref="FlagValueAttributeGroup"/>
     <xs:attribute name="required" type="YesNoType" default="no"/>
     <xs:attributeGroup ref="DeprecationAttributeGroup"/>
   </xs:complexType>
@@ -507,6 +504,17 @@
     </xs:attribute>
   </xs:attributeGroup>
 
+  <xs:attributeGroup name="FieldValueAttributeGroup">
+    <xs:attribute name="as-type" type="FieldDatatypesType" default="string"/>
+    <xs:attribute name="default" type="StringDatatype" default="string"/>
+  </xs:attributeGroup>
+
+  <xs:attributeGroup name="FlagValueAttributeGroup">
+    <!-- datatype should default to 'string' -->
+    <xs:attribute name="as-type" type="SimpleDatatypesType" default="string"/>
+    <xs:attribute name="default" type="StringDatatype"/>
+  </xs:attributeGroup>
+
   <xs:simpleType name="NaturalNumberOrUnboundedType">
     <xs:union memberTypes="PositiveIntegerDatatype">
       <xs:simpleType>