Decision Modelling & Notation
16 important questions on Decision Modelling & Notation
Why decision modelling?
What are the three levels on which decisions are made?
- Tactical decisions: Middle hierarchy
- Operational decisions: Follow the known rules, on the bottom of the hierarchy
How do you model a decision?
- As an activity with a table in the top left corner.
- After that follows a gateways, this is only for the solution, not for intermediate steps
- Use Decision Modeling & Notation (DMN)
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What is the difference between decisions and processes?
Rules change more often, so decisions too, than processes, or at least at different points in time.
What are the objectives of DMN?
- Support BPMN 2.0 Business Rule Task in a standardised supportable way, as well as other types of process
- Provide graphical business decision notations for Model Driven Architecture (MDA) Platform Independent Models (PIMs).
- Bridge standards such as Semantics of Business Vocabulary and Rules (SBVR) and PRR, to help compete the analysis automation/verifcation gap.
Why would you separate decisions-processes?
- They have different responsibilities, and different stakeholders.
- They have different timing
- There will be a simpler decision modeling and discovery
- There will be improved agility (change decision without process)
- You can reuse it
- There will be improved visibility and focus
- You can automate manual decisions (if there is no process)
- Also it will be more stable
What would be a disadvantage to separate decisions-processes?
What are the guidelines for modelling requirements for automated decision-making?
What is the guideline for implementing automated decision-making?
What are the differences between BPMN, CMMN, and DMN? And what is the expression language?
CMMN models descriptive (case management) process. Desriptive or declarative means that noting is fixed, and everything is flexible. The expression language was judged as "should have".
DMN models decision tables (as a core feature). The expression language was a "must have". This one is inbetween the upper two.
What different things do decisions need? Explain.
- Input date: transactions, master data, external data
- Decision logic: Rules, knowlegde, policies, analytics
- Outcome of other decisions: reusability.
What are the different single hit decision tables? Explain them.
- Any hit tables: every case may be included in more than one rule, but the outcomes are equal. Rules are allowed to overlap (this is ugly)
- Priority hit tables: multiple rules can match, with different outcome values. This policy returns the matching rule with the highest output value priority.
- First hit tables: multiple (overlapping) rules can match, with different outcome values. The first hit by rule order is returned (and evaluation can halt) (this is bad!)
What is FEEL and S-FEEL and what is the difference?
- Built-in types, functions and operators
- Every decision in a DRD (Decision Requirements Diagram) can be defined using a formal expression that specifies how the decision’s output is determined from its inputs
- Complete decision models can be defined
- Formal expressions may also be encapsulated as functions
- Supports abstraction, composition, and scalability
S-FEEL is a basic subset of FEEL designed to cover the essential requirements of Decision Table-based DMN models, this is more for ordinary day-to-day things.
What are the three levels of conformance?
Level 2: notation and interchange and S-FEEL
Level 3: notation and interchange and FEEL
What issues does DMN solve?
- Separating decision structure and decision logic (allows to model decision relations, even if not all logic is expressed in tables)
- Decision modelling methodology (keep the insights of the past and avoid confusion, good decision table models are a proven technique to represent decision rules)
- Decision tabe types (recognize and unambiguously exchange, DMN allows multiple table types)
- Standard notation for exchange and implementation (Strict notation and simpe expression language ((S-)FEEL))
What are the criteria to choose between different models according to Reijers (2005)?
- Business process operations: implement the workflow in an efficient way
- Business process behaviour: optimize the time aspect of the execution
- Organization: optimize the organizational structure and the involved resources
- Information: use best practices for the usage of information in business processes
- External environment: improve collaboration and communication with third parties
Note: you can use these criteria to evaluate the model
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