Work Product (Artifact): Platform Independent Model

The Platform Independent Model is a representation of the semantically essential elements of a model that does not contain technology or design-specific detail.

Purpose

The purpose of the Platform Independent Model (PIM) is inherent in the goal of Model-Driven Architecture (MDA). The PIM exists to provide a coherent reusable application with correct structural and behavioral semantics to enable its effective reuse on different platforms and/or to provide the ability to easily host multiple applications on the same platform.

Relationships

Contained Artifacts	Analysis Collaboration
Input To	Mandatory: None	Optional: Optimize Concurrency Architecture Optimize Dependability Architecture Optimize Deployment Architecture Optimize Distribution Architecture Optimize Secondary Architectural Views Optimize Subsystems and Component Architecture	External: None

Main Description

The PIM contains the structural elements required for correctness of the application, their essential behaviors, and fundamental relations (e.g. associations, aggregations, compositions, and generalizations). The PIM should be semantically correct and complete enough to execute the functionality of the system, although it may not meet its Quality of Service (QoS) because performance depends heavily of platform- and design-specific considerations.

The PIM is one of the primary work artifacts produced during Object Analysis. It is (relatively) devoid of design but contains the essential elements required in any correct solution to the problem. In the Harmony Design Phases, specific technological solutions are added to the PIM transforming it into a Platform Specific Model (PSM). This transformation generally occurs either by translation or elaboration; Harmony recommends a combination of both approaches to efficiently arrive at an optimal design (PSM).

Properties

Optional
Planned

Key Considerations

The PIM should contain the structural elements (e.g. classes, objects, functions, variables), their behavior (e.g., specified in state machines, activity diagrams, and/or an action language), and the relations among these elements (e.g. association, aggregation, composition, generalization) that are essential for correctness. This model should execute and replication the expected functionality requirement of the system. It typically will not meet its QoS but should meet all of the functional requirements.

Tailoring

Impact of not having

Not having a separately maintained PIM means that it will be more difficult to target the software to a new computing platform, hardware environment, or software environment. When there is a single anticipated target environment, a separate PIM probably isn't desired.

Reasons for not needing

Having a separately maintained PIM means that should a problem be identified in a derived PSM that affects the PIM, either the PIM must be modified and the PSM transformations reapplied to regenerate the PSM or the changes must be applied independently to both the PIM and PSM. When there are anticipated to be multiple target platforms, or a single target platform that is expected to change throughout its lifecycle, maintaining a separate PIM is probably worth the extra cost.

More Information

Checklists	Activity Diagram Class Diagram Collaboration PIM Review Platform Independent Model Scenario State Diagram
Concepts	Kinds of Models
Guidelines	Naming Conventions Scenario