SACM — Argument metamodel needs improvement

The argument metamodel has some limitations that should be addressed to
make it more coherent and simple. The following aspects need to be
addressed:

1. The annotation class is generally useful and should be promoted up
the class diagram so it can be used more widely

2. AssertedRelationships seem to be kinds of assertions (see related
issue 16848) and so a number of related modelling updates will be needed
to reorganise the model to reflect this, and to simplify by removing or
renaming some of the abstract classes. An abstract Assertion class could
be a useful common parent for both Claim and AssertedRelationship
Classes. A simplification can be made then to rename the existing
ArgumentLink as AssertedRelationship.

3. We should have a simple referencing mechanism to allow referencing
evidence in the evidence metamodel, or to reference other evidence by
means of a URL directly (for when the user is only choosing to comply
with the Argument compliance point)

4. As the models are integrated it will be necessary to rename the top
level element in ARM to be less generic

I propose the following changes:

Create a new Assertion class, as a subclass of ReasoningElement

Set the Claim class to be a subclass of Assertion

Rename the ArgumentLink abstract to be AssertedRelationship (removing
the previous abstract class AssertedRelationship) and move the new
AssertedRelationship class to be a child of the Assertion class

Move the Annotation Class to a shared top level ModelElement, and
include a content:String attribute

Add an optional association from InformationElement to
Evidence::EvidenceItem and add an attribute URL to InformationElement to
be used to refer to evidence not held in the evidence model.

Rename the ModelElement to be ArgumentationElement, and move the
id:String attribute to its new parent ModelElement, which is part of the
shared classes for the argumentation and evidence parts of SACM.

Rename 9.2.1 to “ArgumentationElement class (Abstract)”
Delete paragraph 1 of 9.2.1 and replace with:
“An ArgumentationElement is the top level element of the hierarchy for argumentation
elements”
In the Attributes section:
delete the “identifier: String” attribute
delete the text under “description: String”, and replace with “A description of the
Argumentation entity”
delete the text under “content: String”, and replace with “Supporting content for the
Argumentation entity”
delete the “Associations” heading and its content
change the text of the “Semantics” section to be “The ArgumentationElement is a
common class for all elements within a structured argument”
delete the Invariants section
Delete all of section 9.2.18 (Annotates Class)
Delete all of Section 9.2.5 (ArgumentLink Class (Abstract))
Insert a new Section 9.2.5 as follows:
“Assertion Class (Abstract)
Assertions are used to record the propositions of Argumentation (including both the
Claims about the subject of the argument and structure of the Argumentation being
asserted). Propositions can be true or false, but cannot be true and false simultaneously.
Superclass
ReasoningElement
Semantics
Structured arguments are declared by stating claims, citing evidence and contextual
information, and asserting how these elements relate to each other.
“
Edit section 9.2.6 ReasoningElement Class (Abstract) as follows: First sentence, change “namely Claims and ArgumentReasoning” to “Assertions and
ArgumentReasoning”
Delete Attributes section and its content.
Delete the content of the “semantics” section, and replace with “The core of any
argument is the reasoning that exists to connect assertions of that argument. Reasoning is
captured in SACM through the linking of fundamental claims and the description of the
relationships between the claims. ReasoningElements represent these two elements.”
Edit section 9.2.7 InformationElement Class as follows:
Add an “attributes” section with the following content:
url : string
An attribute recording a URL to external evidence
Add a new sentence at the end of the Semantics section as follows:
“The url attribute is only to be used when only the argumentation aspects of SACM are
complied with. If compliance is claimed against both the argumentation and evidence
packages, then an association to Evidence::EvidenceItem shall be used to reference
evidence by means of a URL”
Add an "associations:" section with the following content:
evidence:Evidence::EvidenceItem[0..*]
The EvidenceItems referenced by the current InformationElement object.
Edit Section 9.2.9 Claim Class as follows
Superclass section > Delete “ReasoningElement”, insert “Assertion” Attributes section>
add “toBeSupported: Boolean An attribute recording whether further reasoning has yet to
be provided to support the Claim (e.g. further evidence to be cited).”
Semantics section, first para -> Delete first sentence (begins “Structured arguments are
declared…”)
Semantics section, 2nd para-> delete “reasoning (in the recorded Argument)”, insert
“argumentation”
Semantics section: add 3rd para: “A Claim that is intentionally declared as requiring
further evidence or argumentation can be denoted by setting toBeSupported to be true. “
Add new “Invariant” Section with the content “Self.assumed and self.toBeSupported
cannot both be true simultaneously”
Edit 9.2.12 AssertedRelationship Class (Abstract) as follows
Superclass section -> delete “ArgumentLink”, insert “Assertion”
Insert new “Associations” section after “Superclass” section, with the following content:
Associations
source:ArgumentElement[0..*] Reference to the ArgumentElement(s) that are the
source (start-point) of the relationship.
target:ArgumentElement[0..*] Reference to the ArgumentElement(s) that are the
target (end-point) of the relationship.
Semantics section, delete first sentence, replace with “In SACM, the structure of an
argument is declared through the linking together of primitive ArgumentElements.”
Edit section 9.2.13 AssertedInferenceClass as follows:
Delete first para, replace with “The AssertedInference association class records the
inference that a user declares to exist between one or more Assertion (premises) and another Assertion (conclusion). An assertion may be the target in more than one
AssertedInference. It is important to note that such a declaration is itself an assertion on
behalf of the user.”
Semantics section, delete existing content, replace with “The core structure of an
argument is declared through the inferences that are asserted to exist between Assertions
(e.g. Claims). For example, an AssertedInference can be said to exist between two claims
(“Claim A implies Claim B”). An AssertedInference between two claims (A – the source
– and B – the target) denotes that the truth of Claim A is said to infer the truth of Claim
B.”
Change title of 9.1 from 'Overview' into 'Argumentation Class Diagram'
Replace Figure 9.1 with the following new figure <<figure on p 125 of ptc/2012-06-04>>