Unified Modeling (Part I) Overview of UML & Modeling Elizabeth Bigelow Carnegie Mellon University

Today’s Lecture Modeling Software Architecture Introducing UML Software Development Life Cycle

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

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

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)

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

Why is Modeling Important? We cannot visualize a system in its entirety--limits to the human ability to understand complexity

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

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

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

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.

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)

Modeling a System’s Architecture Design View Implementation View Use Case View Process View Deployment View

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

Process View Threads and processes that form a system’s concurrency and synchronization mechanisms Addresses performance, scalability and throughput of the system (focus on active classes)

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

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)

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

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)

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

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

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

Examples Pilot Wright Flyer 1 Flies * Take Off () Land () Turn() Name Weight Increase Throttle() Brake () Decrease Throttle() 1 1 1 1 2 2 Wing Canard Rudder Engine

High Level Statechart for Wright Flyer Taking Off Flying Idle (Parked) Landing

<<extends>> Wright Flyer Starts Engine Flexes Wing Orville Releases Catapult Says Start Engine Wilbur USE CASE DIAGRAM

The Lifecycle According to Booch, Rumbaugh and Jacobson Inception Business Modeling & Requirements Elaboration Analysis, Design, Implementation, Test Construction Transition Implementation, Test, Deployment

Next Time Basic Structural Modeling