GSN Metamodel. In the following subsections we describe the model elements. All references are to sections within the GSN Community Standard.

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1 1. Background GSN Metamodel This section defines a metamodel for representing structured arguments using GSN. GSN arguments should be instances of this GSN Metamodel. Instances of the GSN Metamodel are conformant with this GSN standard. The GSN Metamodel facilitates the interchange of structured arguments between diverse tools by different vendors. It also facilitates the translation of GSN arguments to SACM models and to other argument notations. The GSN Metamodel is an extension of the Structured Assurance Case Metamodel (SACM) [1]. 2. GSN Metamodel This section defines the GSN Metamodel GSN Metamodel Class Diagram Figure 1 shows the GSN Metamodel Class Diagram. All elements represented with a red border are GSN elements. All other elements are elements of the existing SACM Metamodel. Figure 1 GSN Metamodel Class Diagram In the following subsections we describe the model elements. All references are to sections within the GSN Community Standard Class (Abstract) The Class is used to record the propositions of GSN arguments. The Class extends the SACM Claim Class.

2 Claim tobeinstantiated: Boolean As part of a pattern, any claim may be declared as to be instantiated. See section A GSN_Goal Class GSN_Goals are used to record logical propositions. The GSN_Goal Class extends the Class GSN_Justification Class GSN_Justifications are used to record statements of justification. The GSN_Justification Class extends the Class GSN_Assumption Class GSN_Assumptions are used to record assumptions. The GSN_Assumption Class extends the Class GSN_ContextAsAssertion Class GSN_ContextAsAssertions are used to record asserted statements of information. The GSN_ContextAsAssertion Class extends the Class GSN_ContextAsReference Class GSN_ContextAsReference are used to record references to contextual information. The GSN_ContextAsReference Class extends the SACM InformationElementCitation Class. InformationElementCitation

3 GSN_Solution Class GSN_Solutions are used to record references to evidence. The GSN_Solution Class extends the SACM InformationElementCitation Class. InformationElementCitation GSN_ModuleReference Class GSN_ModuleReferences are used to record references to GSN Modules. The GSN_ModuleReference Class extends the SACM InformationElementCitation Class. InformationElementCitation cites: GSN_Module[1]!Reference to the GSN_Module that is cited by the GSN_ModuleReference. GSN_ModuleReferences cite instances of class GSN_Module. See section B GSN_Module Class GSN_Module is the container class for arguments represented using the GSN Metamodel. The GSN_Module Class extends the SACM Argumentation Class. Argumentation GSN_Modules may be associated with instances of class GSN_ModuleReference. See section B GSN_InContextOf Class GSN_InContextOf association class declares that the information referenced by a GSN_ContextAsReference or GSN_ContextAsAssertion provides context for a or GSN_Strategy element. The GSN_InContextOf Class extends the SACM AssertedContext Class. AsseertedContext multiplicity: Integer optional: Boolean source: ArgumentElement[1]! Reference to the ArgumentElement that is the source (start-point) of the relationship. target:argumentelement[1]

4 !Reference to the ArgumentElement that is the target (end-point) of the relationship. As part of a pattern, the multiplicity of the GSN_InContextOf relationship may be declared. As part of a pattern, a GSN_InContextOf relationship may be declared optional. See sections 1.2, A1.2, and B1.2. Invariants context GSN_InContextOf inv SourceMustBeGoalOrStrategy : self.source->forall(s s.oclistypeof(gsn_goal) or s.ocllstypeof(gsn_strategy) inv TargetMustBeContext : self.target->forall(t t.oclistypeof(gsn_contextasassertion) or t.oclistypeof(gsn_assumption) or t.oclistypeof(gsn_justification) or t.oclistypeof(gsn_contextasreference) or t.oclistypeof(gsn_modulereference) or t.oclistypeof(gsn_awaycontext)) GSN_SupportedBy Class GSN_SupportedBy association class records the inference that a user declares between one or more and another. GSN_SupportedBy association class also records the declaration that one or more GSN_Solution provides information that helps establish the truth of a. The GSN_SupportedBy Class extends the SACM AssertedInference and AssertedEvidence Class. AssertedInference, AssertedEvidence multiplicity: Integer optional: Boolean source: ArgumentElement[1]! Reference to the ArgumentElement that is the source (start-point) of the relationship. target:argumentelement[1]!reference to the ArgumentElement(s) that is the target (end-point) of the relationship. SACM classes AssertedInference and AssertedEvidence are both represented using the same GSN element. It can always however be determined which SACM class is represented from type of the target of the relationship ( or GSN_Solution). As part of a pattern, the multiplicity of the GSN_SupportedBy relationship may be declared. As part of a pattern, a GSN_SupportedBy relationship may be declared optional. See sections 1.2, A1.2, and B1.2. Invariants context GSN_SupportedBy inv SourceMustBeGoalOrStrategy : self.source->forall(s s.oclistypeof(gsn_goal) or s.ocllstypeof(gsn_strategy) inv TargetMustBeGoalOrStrategyOrSolution : if self.source.ocllstypeof(gsn_goal) then self.target->forall(t t.oclistypeof(gsn_goal) or t.oclistypeof(gsn_solution) or t.oclistypeof(gsn_strategy)) if self.source.ocllstypeof(gsn_strategy) then self.target->forall(t t.oclistypeof(gsn_goal))

5 GSN_ChallengedBy Class GSN_ChallengedBy association class records the challenge (i.e. counter-argument) that a user declares between one or more and another. GSN_ChallengedBy association class can also be used to associate GSN_Solutions to a, where this GSN_Solution is being asserted to infer that the is false (i.e. counter-evidence). The GSN_ChallengedBy Class extends the SACM AssertedChallenge and AssertedCounterEvidence Class. AssertedChallenge, AssertedCounterEvidence multiplicity: Integer optional: Boolean source: ArgumentElement[1]! Reference to the ArgumentElement that is the source (start-point) of the relationship. target:argumentelement[1]!reference to the ArgumentElement(s) that is the target (end-point) of the relationship. SACM classes AssertedChallenge and AssertedCounterEvidence are both represented using the same GSN element. It can always however be determined which SACM class is represented from type of the target of the relationship ( or GSN_Solution). As part of a pattern, the multiplicity of the GSN_ChallengedBy relationship may be declared. As part of a pattern, a GSN_ChallengedBy relationship may be declared optional. See section? Invariants context GSN_ChallengedBy inv SourceMustBeGoalOrStrategy : self.source->forall(s s.oclistypeof(gsn_goal) or s.ocllstypeof(gsn_strategy) inv TargetMustBeGoalOrStrategyOrSolution : self.target->forall(t t.oclistypeof(gsn_goal) or t.oclistypeof(gsn_solution)) GSN_Strategy Class GSN_Strategys are used to provide additional description of the GSN_SupportedBy or GSN_ChallengedBy relationships. It is also possible that GSN_Strategy elements can refer to GSN_Modules as a means of documenting the detail of the argument that establishes the GSN_SupportedBy relationships. The GSN_Strategy Class extends the SACM ArgumentReasoning Class. ArgumentReasoning See sections 1.2 and B GSN_AwayGoal Class GSN_AwayGoal cites a within another GSN_Module, for use with the current GSN_Module. The GSN_AwayGoal Class extends the SACM ArgumentElementCitation Class.

6 ArgumentElementCitation Cites: GSN_Goal[1] References to the GSN_Goal within another GSN_Module that is cited by the GSN_AwayGoal. See section B GSN_AwaySolution Class GSN_AwaySolution cites a GSN_Solution within another GSN_Module, for use with the current GSN_Module. The GSN_AwaySolution Class extends the SACM ArgumentElementCitation Class. ArgumentElementCitation Cites: GSN_Solution[1] References to the GSN_Solution within another GSN_Module that is cited by the GSN_AwaySolution. See section B GSN_AwayContext Class GSN_AwayContext cites a GSN_ContextAsReference within another GSN_Module, for use with the current GSN_Module. The GSN_AwayContext Class extends the SACM ArgumentElementCitation Class. ArgumentElementCitation Cites: GSN_Solution[1] References to the GSN_Context within another GSN_Module that is cited by the GSN_AwayContext. See section B GSN_Choice Class GSN_Choice is used as part of a GSN pattern to indicate a number of possible SACM ArgumentReasoning approaches may be adopted. The GSN_Choice constrains the possible AssertedRelationship elements that may be instantiated. The GSN_Choice Class extends the SACM ArgumentReasoning Class. ArgumentReasoning constrains: AssertedRelationship[1..*] Constrains the Asserted Relationship.

7 See section A References 1. Object Management Group (OMG), Structured Assurance Case Metamodel (SACM) Version 1.0, OMG Document Number: formal/ !standard document, URL: February 2013