Home
What's New
Use Case Basics 101
UC Concepts 201
UC Concepts 301
Simulation
BA SMEs Waste $$$
Business Processes
Software Testing
Outsourcing Risk
Founder's Profile
Testimonials
Press Releases
Our Services
Contact Us
 

UML Specification Excerpts about System

1. V1.5 UML Specification

Quotes are directly from the noted UML Specification in black font color. [My comments are in blue font color like this sentence.]

system
A top-level subsystem in a model. Contrast: physical system.

[Circular definitions are not very useful: A system is a subsystem? This is especially true because the term subsystem is not defined.]

model
An abstraction of a physical system with a certain purpose. See: physical system.

physical system

[Undefined in the Glossary! Don’t you love it?]

A. Section 2.15.1 Model Management Overview
In this section, it is necessary to clearly distinguish between the physical system being modeled; that is, the subject of the model and the model element that represent the physical system in the model. For this reason, we consistently use the term physical system when we want to indicate the former and the term (top-level) subsystem when we want to indicate the latter.

2. UML 2.0 Specification

system An organized array of elements functioning as a unit.
Also, a top-level subsystem in a model.

[Adding the organized array sentence helps. It is conceptually close to what we need. However, it uses developer centric language with the term array that business people may not be familiar with.]

element
A constituent of a model.

[This is a developer centric viewpoint. Elements exist first; then they are modeled. This is true even for a new thing that is not built yet. How is it possible to model a concept before the concept exists?]

model

[Undefined in the Glossary but was defined in the UML 1.5 Glossary.]

A. 17.3.1 Model (from Models)
A model captures a view of a physical system. It is an abstraction of the physical system, with a certain purpose. This purpose determines what is to be included in the model and what is irrelevant. Thus the model completely describes those aspects of the physical system that are relevant to the purpose of the model, at the appropriate level of detail.

physical system

1. The subject of a model.
2. A collection of connected physical units, which can include software, hardware and people, that are organized to accomplish a specific purpose. A physical system can be described by one or more models, possibly from different viewpoints.
Contrast: system

3. Jacobson in Object-Oriented Software Engineering

7.2.2 Actors
Thus we will have to make a system delimitation to define where the boundary is between actors and use cases.

[To Jacobson, actors are outside of use cases.]

4. Systems Engineering

System
Generally, a system is a set or assemblage of elements that exhibit behavior collectively. All of the definitions found in the systems engineering literature are built on this idea.

[This definition of system is the most useful. In particular, I like its emphasis on exhibiting behavior collectively. This ties in closely to the idea that a use case must deliver a perceivable benefit of value, i.e., defined behavior.]

From System UML Specification Excerpts to UML Specification Excerpts


footer for uml specification page