Value Model Framework

SUPPORTING THE ELICITATION PROCESS WITH SysML

It becomes evident that the formal capturing and defining of the elements of a value network are the first critical steps in the process that ultimately leads to a value (objective) function that can be maximized in order to make rational decisions. Below are listed the formal SysML stereotypes used to define the elements of the value network.

VDD Profile in SysML1. Domain – In the profile, the domain is assigned the type «block» and owns (with the directed composition relationship) the system and all the stakeholders. Thus there is nothing under consideration that is not owned by the domain.
2. Stakeholder – To model the stakeholders, the stereotype «Stakeholder» is an extension of the SysML element “Class” and therefore has part properties, value properties, reference properties, etc. that are available to use to properly identify all of the relationships a stakeholder has in the value network.
3. Decision Maker – To identify the key stakeholder whose point of view we are concerned about, the «decisionMaker» stereotype is used as an extension of the «stakeholder» stereotype. This is done in order to identify the decision maker as a stakeholder as well (albeit a special kind). As an extension of a class, the «decisionMaker» stereotype is also typed “class” and inherits all the property types of the «stakeholder» stereotype.
4. Measure of Utility – Each stakeholder is given a value property to which the stereotype «measureOfUtility» is applied as an extension of the SysML construct “Property” to note that that particular value property is the stakeholder’s measure of value, or utility. The name and value type of the value property designate what the property, or attribute, is and how it is measured.
5. Decision Maker’s Measure of Utility – Similar to the relationship between stakeholder and decision maker, a separate  stereotype was created to identify the decision maker’s measure of utility, called «dmUtility». Its form and function are the same as the «measureOfUtility» stereotype but its serves to make a distinction between any stakeholder’s measure of utility and the measure of utility that will ultimately be used in the decision being made.
6. Stakeholder Choice – Each stakeholder in the network is given a value property that has the stereotype «choice» applied.
The stereotype is an extension of the SysML construct “Property”. These properties represent actions that can be taken by that particular stakeholder.
7. Decision Maker Choice – Just like the decision maker’s measure of utility, the «dmChoice» stereotype is a specialization of “choice” and is unique to the actions that the
decision maker can take in the form of choices. These choices can include design decisions or financial decisions, among other actions. These properties are crucial to identify and capture because the decision maker is trying to determine the best combination of choices to make in order to maximize his utility.
8. Wider system of interest – This stereotype («widerSoi») is an extension of “class” in SysML and is very loosely defined. How “wide” to let the wider system of interest be is up to the decision maker. It cannot be the same set of elements that make up the system of interest but the system must be a subset of the wider system.
9. System of Interest – This stereotype («soi») is an extension of “class” in SysML and should only be applied to one entity in the network. The properties of the “class” element are used to distinctly set apart the system of interest and its parts from the wider system of interest.
10. “Influenced By” Relationship – This stereotype («influencedBy») is an extension of the SysML construct “Dependency” and is applied to the relationships between other
model elements to denote that the “client” is dependent on, or influenced by, the “supplier”. This is a key element in the value network as it is the basic relationship between elements that allows a decision maker to see how his value is being affected by all other elements in the network.
11. “Impacted By” Relationship – This stereotype («impactedBy») is very similar to the «influencedBy» stereotype in its foundations in SysML. However, its use in the
value network is different in this way: this stereotype represents a temporal relationship between two elements.