4. MDA Model Transformation and Execution

The "magic" of MDA lies in automating the transition from high-level stakeholder requirements to running systems.

Approaches to Execution

There are two primary ways to move from a model to a running system:

1. Transformation: Using a pattern to generate source code or schemas.
2. Model Execution: Using an engine to interpret the model directly as "source code."

The PIM to PSM Pattern

• PIM (Platform Independent Model): Describes the "What" and "Why."
• PSM (Platform Specific Model): Describes the "How" for a specific tech stack.
• Transformation Specs: The rules that map the PIM to the PSM.

Example: The Person Entity

Imagine a neutral PIM defining a Person with a Name and Address.

• Transformation A (Java): Generates POJOs with Hibernate annotations.
• Transformation B (XML): Generates an XSD schema.
• Transformation C (SQL): Generates CREATE TABLE scripts.

Benefits and Trade-offs

• Pros: High stakeholder engagement (they can read the PIM), reusable transformations, and consistent, high-quality output.
• Cons: Upfront investment is required to define or acquire transformation rules; stakeholders must learn to interpret business models.