Si Alhir, Sinan - Model Views of the Unified Modelling Language (UML)
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The Structure of Concern Project compares many theoretical models from many disciplines to the Adizes PAEI model, arguing that they must all be reflecting the same underlying phenomenon. One concern structure model is described below.


The Unified Modelling Language (UML) is a standard set of diagrams used by business analysts, systems analysts and computer programmers to spell out ideas and plans for new systems. In his reference guide to the UML, Sinan Si Alhir divides these standard diagrams into five categories. Each category represents a different system view – a different way of looking at a system. He introduces five such categories, the first being the User View (Use Case Diagrams in the UML). The remaining four views are aimed towards the system as such (Si Alhir, 1998). These are listed below in PAEI order:

P – Implementation View
A – Behavioral View
E – Structural View
I – Environment View

P – Implementation Model View: This view deals with how a system will be realized in terms of its physical instantiation, including physical code snippets (source, binary or executable), data, documents etc. The UML diagram that represents this view of the system is the Component Diagram, showing the organization and dependencies among tangible software implementation components. This diagram describes the implementation in concrete terms.

A – Behavioral Model View: Behavioral models specify system activity in careful detail, to foresee problems or conflicts before they arise. Sequence Diagrams depict classes exchanging information as interactions flow through a system. Collaboration Diagrams show how components communicate and interact to accomplish joint purposes. State Diagrams describe how classes respond to input; the states they enter and their transitions, for the whole object lifecycle. Activity Diagrams show information processing within a class, describing action states and action/object flows. Together, these diagrams offer a meticulous preview of the behavior of the system for troubleshooting prior to implementation.

E – Structural Model View: This is a static, conceptual overview of the system. Models depict classes, objects and relationships between classes (via Class Diagrams and Object Diagrams) - a schematic, high-level overview of the system for orienting design efforts.

I – Environment Model View: This view describes the configuration of the system and the relationships between information compnents, mapping all of the contextual conditions that may impact system function. Deployment Diagrams are used towards this end. Since end-users are also part of the system’s context, the User View/Use Case Diagrams can also be put in this group.

Bibliography
1. Si Alhir, S. (1998). UML in a Nutshell: A desktop quick reference. Sebastopol, California: O’Reilly.
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