Unified Modeling Part I Overview of UML

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Unified Modeling (Part I)Overview of UML
Modeling

• Elizabeth Bigelow
• Carnegie Mellon University

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Todays Lecture

• Modeling
• Software Architecture
• Introducing UML
• Software Development Life Cycle

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Modeling

• Why model?
• Kinds of models
• Why is it important?
• Principles of Modeling
• Object-Oriented Modeling

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Why Model?

• To communicate the desired structure and behavior
  of a system
• To visualize and control the architecture
• To better understand a system and manage risk
• To reason about alternatives

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Kinds of Models

• Iconic (example model airplane)
• Analogic (example electrical network modeling
  the flow of liquid through pipes some
  properties, some structure)
• Analytic (example set of differential equations
  claiming to describe how prices change)

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What is a model?

• A simplification of reality (abstraction)-- not
  the truth, the whole truth and nothing but the
  truth
• At the same time, we choose to make certain parts
  rigorous

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Why is Modeling Important?

• We cannot visualize a system in its
  entirety--limits to the human ability to
  understand complexity

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Principles of Modeling

• Choice of model has profound influence on how a
  problem is attacked and how solution is shaped
• Every model may be expressed at different levels
  of precision
• The best models are connected to reality
• No single model is sufficient

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The hard part

• Many models of the same thing are nearly
  independent (at least in preparation)
• The hard part fitting them all together

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Object Oriented Modeling

• The primary strength of object oriented modeling
  is helping to pull the various models together
• Traditional methods algorithmically based--tend
  to be brittle, hard to change
• Does not mean that implementation must be object
  oriented, or even in an object oriented language

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Software Architecture

• Shaw Garlan
• Software Architecture is the system level
  organization of components (units of code) and
  connectors (method invocation, RPC,
• network protocols, etc.)
• Another definition is that software architecture
  is the highest level of system organization in
  which one can discern or impose order.

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Architectural Decisions

• Organization of a software system
• Selection of structural elements and their
  interfaces by which the system is composed
• Behavior (collaboration among elements)
• Composition into progressively larger subsystems
• Architectural style (patterns, pipe-filter,
  functional decomposition, object-oriented, main
  line procedure call, event system)

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Modeling a Systems Architecture
Design View
Implementation View
Use Case View
Process View
Deployment View
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Design View

• Classes, interfaces collaborations
• Services that should be provided to end users
• Static aspects captured in class diagrams and
  object diagrams
• Dynamic aspects are captured in interaction
  diagrams, statecharts, and activity diagrams

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Process View

• Threads and processes that form a systems
  concurrency and synchronization mechanisms
• Addresses performance, scalability and throughput
  of the system (focus on active classes)

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Implementation View

• Components and files used to assemble and realize
  the physical system
• Diagrams component diagrams (static) and
  interaction diagrams, statechart diagrams and
  activity diagrams

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Deployment View

• Hardware topology on which the system executes
• Distribution, deliver and installation of the
  parts that make up the physical system
• Deployment diagrams (static) and interaction,
  statechart, and activity diagrams (dynamic)

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Use Case View

• Use cases describe the system as seen by its end
  users, analysts and testers
• Static aspects are captured in use case diagrams
  and dynamic are captured in interaction diagrams,
  statechart diagrams and activity diagrams

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UML Conceptual Model

• Building blocks--things, relationships and
  diagrams
• Rules on how the blocks may be put together
  (names, scope, visibility, integrity, execution)
• Common mechanisms (specifications, adornments,
  common divisions, extensibility mechanisms)

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Classes and Objects

• A class is a set of objects that share the same
  attributes, relationships and semantics.
• An object is an instance of a class--an entity
  with a well defined boundary and identity that
  encapsulates state and behavior

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Key Abstractions

• Structural Things (class, interface)
• Behavioral Things (dynamic, interaction-messages,
  state machines)
• Grouping Things (packages)
• Annotational Things (comments, constraints)
• Relationships (dependency, association,
  generalization, realization

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Diagrams

• Class diagrams
• Object diagram
• Use case diagram
• Sequence diagram
• Collaboration diagram
• Statechart diagram
• Activity diagram
• Component diagram
• Deployment diagram

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Examples
Pilot
Wright Flyer

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Flies
Name Weight
Take Off () Land () Turn()
Increase Throttle() Brake () Decrease Throttle()
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1
1
1
2
2
Wing
Canard
Rudder
Engine
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High Level Statechart for Wright Flyer
Taking Off
Flying
Idle (Parked)
Landing
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ltltextendsgtgt
Wright Flyer
Starts Engine
Flexes Wing
Orville
Releases Catapult
Says Start Engine
Wilbur
USE CASE DIAGRAM
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The Lifecycle According to Booch, Rumbaugh and
Jacobson

• Inception
• Business Modeling Requirements
• Elaboration
• Analysis, Design, Implementation, Test
• Construction
• Analysis, Design, Implementation, Test
• Transition
• Implementation, Test, Deployment

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Next Time

• Basic Structural Modeling