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Putting the Pieces Together

As we have continued to refine our concept of SSVC, we have an increasing understanding of the importance of Decision Points as the foundational blocks from which the rest of the SSVC concept is built. A second, but less foundational, concept are the Outcomes that provide a vocabulary to describe the results of a decision.

Decision Points and Outcomes as Bricks

Over time, we have come to think of decision points and outcomes as the LEGO® bricks of SSVC decision models.

LEGO® Bricks

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LEGO® Bricks come in different shapes and sizes, and they can be combined in different ways to build different structures. Similarly, decision points come in different shapes and sizes, and they can be combined in different ways to build different decision models. And just as some bricks can be substituted for others to add variation, some decision points are substitutable for others.

We have realized that part of the value of enumerated decision points is that they provide a way to organize the information that is relevant to a decision. This organization is important because it helps us to understand the decision and to communicate the decision model to others.

Decision points and outcomes have a few key characteristics that make them useful for organizing information:

  • Independence: Each decision point represents a different aspect or dimension of the decision being modeled. This means that the decision points are not redundant with each other. They may each be relevant to the decision, but they are relevant in different ways.
  • Discreteness: Each decision point has a finite and discrete set of possible values. These specific values that can then be mapped onto data collection and analysis results so that the data can be used to inform the decision.
  • Well-Definedness: Each decision point has a clear meaning and a clear, ordered set of possible values. This means that the decision point values are not ambiguous or open to interpretation.

In our brick analogy, the toy bricks are similarly independent, discrete, and well-defined. Independence means that different bricks can serve different purposes in the model. The pips on the bricks provide discrete points of attachment to allow bricks to connect together. Well-definedness (specification and manufacturing consistency) allows bricks to be combined effectively.

Model Kits and How to Use Them

When you buy a model kit at the store, you get

  • a box with a picture of the model on the front, and sometimes variation suggestions on the back
  • a set of bricks, usually organized into bags appropriate for the different stages of the build
  • a set of instructions to tell you how to combine the bricks to build the model(s) pictured on the box

From that starting point, there are a few different ways you might proceed:

Follow the examples as provided

For many people, this is the experience they want. They want to build the model exactly as it is pictured on the box, and so they will simply follow the instructions provided.

Adapt the examples to suit your needs

But other folks might want to build something else with the bricks. They might want to adapt the model slightly for their own purposes, perhaps turning an airplane with wheels into a seaplane by adding floats, or turning a car into a spaceship by adding a rocket booster. To do that, they might follow the instructions provided, just adapting them slightly with their own variations. Sometimes they might add a few extra bricks from their own collection to make the model more like what they want.

Combine different kits to build something new

Perhaps they might want to combine two different model kits to build something new. Knowing which parts of the instructions to follow and which parts to ignore is a matter of understanding the properties of the bricks and the context of the model they want to build.

Build something completely original

A builder might want to create something completely new that is not available in kit form, like a castle guarded by robots. In that scenario, they might think of the kit more as a supply of specific bricks than as a specific model. Advanced builders need to understand more about what they are trying to build and how the bricks can be combined to build it.

The point is that the model kits serve as a starting point with a lot of flexibility, but it is up to the builder to decide how much of that flexibility to use.

SSVC Decision Models as Kits

Similarly, SSVC provides a set of "bricks" in the form of decision points and outcomes. We have provided a set of example decision models and policies to get you started. You might choose to simply use what we've provided as a starting point. Or you might already recognize that our example gets the structure of the decision model right, but you need to adapt the outcomes or policy to better fit your situation.

You might also recognize that you need to combine different example decision models to build the model you need. For example, you might recognize that you need to combine the supplier decision model with the deployer decision model to build a model that is relevant to your situation as both a supplier and a deployer.

Or, perhaps you have a decision problem that we have not yet addressed with any of our examples. In that case, you might examine the decision points we've provided and decide which ones are relevant to your situation. You could choose to customize a decision point to better fit your situation, or you might choose to add a new decision point to better suit your needs.

This is the embodiment of the Stakeholder-Specific concept in SSVC: SSVC provides the components for you to build your own decision models, and we provide some examples to get you started. If the examples are sufficient for your needs, then you can simply use them as they are.

But we recognize that you are the expert in your own situation, and that you are in a better position than we are to decide how to combine the provided components to build the decision model you need. If you need to adapt the components we've provided, or if you need to add new components, then we encourage you to do so. And if you think that your adaptations or additions would be useful to others, then we encourage you to share your suggestions, ideas, and changes with the community.