New Element Individuals to handle NONE and NOASSERTION scenarios for the 'to' property of Relationships

model/Core/Classes/Relationship.md

@@ -11,6 +11,13 @@ Describes a relationship between one or more elements.
 A Relationship is a grouping of characteristics unique to an assertion
 that one Element is related to one or more other Elements in some way.
 
+To explicitly assert that no such relationships exist, the `to` property 
+should contain the 'NONE' individual and no other elements.
+A relationship that contains 'NONE' and additional elements in the `to` property is not valid.
+
+To explicitly assert that no assertions are being made regarding the 
+existence of such relationships, the `to` property should contain the 'NOASSERTION' individual.
+
 ## Metadata
 
 - name: Relationship
@@ -25,7 +32,7 @@ that one Element is related to one or more other Elements in some way.
  - maxCount: 1
 - to
  - type: Element
- - minCount: 0
+ - minCount: 1
 - relationshipType
  - type: RelationshipType
  - minCount: 1

model/Core/Individuals/NoAssertionElement.md

@@ -0,0 +1,26 @@
+SPDX-License-Identifier: Community-Spec-1.0
+
+# NoAssertionElement
+
+## Summary
+An Individual Value for Element representing a set of Elements of unknown 
+identify or cardinality (number).
+
+## Description
+
+NoAssertionElement should be used if 
+the SPDX creator has attempted to but cannot reach a reasonable objective determination;
+the SPDX creator has made no attempt to determine this field; or
+the SPDX creator has intentionally provided no information (no meaning should be implied by doing so).
+
+For example, a Relationship with `from`=Element1, `relationshipType`="ancestorOf", 
+and `to`=NOASSERTION is explicitly expressing that no assertion is being made about any potential descendents of Element1.
+
+## Metadata
+
+- name: NoAssertionElement
+- type: Element
+
+## Property Values
+
+- name: "NOASSERTION"

model/Core/Individuals/NoneElement.md

@@ -0,0 +1,25 @@
+SPDX-License-Identifier: Community-Spec-1.0
+
+# NoneElement
+
+## Summary
+
+An Individual Value for Element representing a set of Elements with 
+cardinality (number/count) of zero.
+
+## Description
+
+NoneLicenseElement should be used if the SPDX creator desires to assert that 
+there are NO elements for the given context of use.
+
+For example, a Relationship with `from`=Element1, `relationshipType`="ancestorOf", 
+and `to`=NONE is explicitly expressing an assertion that Element1 has no descendents.
+
+## Metadata
+
+- name: NoneElement
+- type: Element
+
+## Property Values
+
+- name: "NONE"