Chapter 14: The Movement to Objects

Behavioral State Machine Diagram

A dynamic model that shows the different states that a single class passes through during its life in response to events, along with responses and actions. Typically, they are not used for all classes, but just to further define complex classes to help simplify the design of algorithms for their methods.

Sequence Diagram

A dynamic model that supports the dynamic view of the evolving systems. It shows the explicit sequence of messages that are passes between objects in a defined interaction. Since it emphasizes the time-based ordering of the activity that takes place among a set of objects, it is very helpful for understanding real-time specifications and complex use cases.

Communication

Model the behavior of objects within a use case. Focuses on the communication among a set of collaborating objects of an activity.

Sequence

Model the behavior of objects within a use case. Focuses on the time-based ordering of an activity.

Guard Condition

A Boolean expression that includes attribute values, which allows a transition only if the condition is true.

System Boundary

A box that represents the system and clearly delineates what parts of the diagram are external or internal to it. The name of the system can appear either inside or on top of the box.

Message

A communication between two objects that conveys information. They are passed between objects and shown by solid lines connecting two objects, call links on the sequence diagram.

Class

A general template we use to define and create specific instances, or objects. Every object is associated with it.

A Use Case

A major process that the system will perform that benefits an actor(s) in some way, and it is labeled by a descriptive verb phrase.

Actor

A person or another system that interacts with and derives value from the system. It is not a specific user, but a role that a user can play while interacting with the system. They are external to the system and initiate a use case.

Rational Unified Process (RUP)

A rapid application development approach to building systems that is similar to the iterative development or extreme programming approach. It emphasizes iterative, incremental development and prototyping that undergo continuous testing throughout the life of the project.

Transition

A relationship that represents the movement of an object from one state to another state.

State

A set of values that describe an object at a specific point in time, and it represents a point in an object's life in which it satisfies some condition, performs some action, or waits for something to happen.

Class Diagram

A static model that supports the static view of the evolving system. It shows the classes and the relationships among the classes that remain constant in the system over time.

Dynamic (Late) Binding

A technique that delays identifying the type of object until run-time. As such, the specific method that is actually called is not chosen by the object-oriented system until the system is running.

Operations

Actions or functions that a class can perform.

Protected Attribute

An attribute that is hidden from all other classes except its immediate subclasses. Represented by a # symbol.

Private Attribute

An attribute that is hidden from all other classes. Represented by a - symbol.

Public Attribute

An attribute that is not hidden from any other object. Represented by a + symbol.

Object

An instantiation of a class. In other words, it is a person, place, event, or thing about which we want to capture information.

Constructor Operation

An operation that creates a new instance of a class.

Query Operation

An operation that makes information about the state of an object available to other objects, but it will not change the object in any way.

Update Operation

An operation that will change the value of some or all of the object's attributes, which may result in a change in the object's state.

Concrete Class

Any class that has instances.

Use Case

Capture business requirements for the system and to illustrate the interaction between the system and its environment.

Abstract Classes

Classes that do not produce instances because they are used merely as templates for other, more specific classes (especially those classes located high up in a hierarchy).

Superclasses

Common sets of attributes and methods can be organized into it.

Use Cases

Communicates at a high level what the system needs to do, and each UML diagramming techniques build upon this by presenting the functionality in different ways, each view having a different purpose.

Attributes

Describe information about the object, such as customer name, address, e-mail, and phone number. Each object has it.

Use Case

Describes how the user interacts with the system to perform some activity, such as placing an order, making a reservation, or searching for information. It is used to identify and to communicate the requirements for the system to the programmers who must write the system. Focus on one activity at a time.

Functional view

Describes the external behavior of the system from the perspective of the user. On the surface, this view is closely related to the process-modeling approaches in structured analysis and design.

Dynamic View

Describes the internal behavior of the system in terms of messages passed between objects and state changes within an object. This view in many ways combines the process and data-modeling approaches, because the execution of a method can cause state changes in the receiving object.

Static View

Describes the structure of the system in terms of attributes, methods, classes, relationships, and messages. This view is very similar to data-modeling approaches in structured analysis and design.

Behavioral State Machine

Examine the behavior of one class.

Package

Groups other UML elements together to form higher level constructs.

Interaction Overview

Illustrate an overview of the flow of control of a process.

Activity

Illustrate business work flows independent of classes, the flow of activities in a use case, or detailed design of a method.

Protocol State Machine

Illustrate the dependencies among the different interfaces of a class.

Timing

Illustrate the interaction that takes place among a set of objects and the state changes that they go through along a time axis.

Composite Structure

Illustrate the internal structure of a class--i.e., the relationships among the parts of a class.

Component

Illustrate the physical relationships among the software components.

Class

Illustrate the relationships between classes modeled in the system.

Object

Illustrate the relationships between objects modeled in the system. Function when actual instances of the classes will better communicate the model.

Use Case Diagram

Illustrates in a very simple way the main functions of the system and the different kind of users who will interact with it.

Methods

Implement an object's behavior. It is nothing more than an action that an object can perform. It is very much like a function or procedure in a traditional programming language.

Messages

Information sent to objects to trigger methods. It is essentially a function or procedure call from one object to another object.

Subclasses

Inherit the attributes and methods from the superclass about them. That is, each one contains attributes and methods from its parent superclass.

Aggregation

It is used when classes actually comprise other classes. This association is typically identified when words like "is a part of" or "is made up of" needs to be used to describe the relationship.

Attributes

Properties of a class about which we want to capture information.

Behavior Diagrams

Provide the analyst with a way to depict the dynamic relationship among the instances or objects that represent the business information system. They also allow the modeling of dynamic behavior of individual objects throughout their lifetime. They support the analyst in modeling the functional requirements of an evolving information system.

Visibility

Relates to the level of information hiding to be enforced for the attribute.

Associations

Represent the relationships that classes have with one another.

Deployment

Show the physical architecture of the system. Can also be used to show software components being deployed onto the physical architecture.

Association Relationships

Show which use cases the actor interacts with. It typically represents two-way communication between the use case and the actor.

Multiplicity

Shows how an instance of an object can be associated with other instances.

Generalization

Shows that one class (subclass) inherits from another class (superclass), meaning that the properties and operations of the superclass are also valid for objects of the subclass. This association occurs when words like "is a kind of" needs to be used to describe the relationship.

Behavioral State Machine Diagram

Shows the different states of the class and what events cause the class to change from one state to another.

Focus of Control (Execution Occurrence)

Shows when classes are sending and receiving messages. It is shown by a thin, rectangular box on the sequence diagram.

Event

Something that takes place at a certain point in time and changes a value(s) that describe an object, which in turn changes the object's state. It can be a designated condition becoming true, the receipt of the call for a method by an object, or the passage of a designated period.

Class

Stores the information and manages information in the system. It is the main building block of a class diagram.

Use Case Diagram

Summarizes all of the use cases (for the part of the system being modeled) together in one picture. It is drawn early on in the SDLC, when the analyst is gathering and defining requirements for the system, because it provides a simple, straightforward way of communicating to the users exactly what the system will do.

Object-Oriented Systems

Systems that focus on capturing the structure and behavior of information systems in little modules that encompass both data and processes. These little modules are known as objects.

Encapsulation

The combining of process and data into a single entity.

Unified Modeling Language (UML)

The objective is to provide a common vocabulary of object-based terms and diagramming techniques that is rich enough to model any systems development project from analysis to design.

Information Hiding

The principle suggests that only the information required to use a software module must be published to the user of the module. This implies that the information required to be passed to the module and the information returned from the module are returned.

A-Kind-of (AKO) Relationship

The relationship between the class and its superclass.

Polymorphism

The same message can be interpreted differently by different classes or objects.

Static Binding

The type of object is determined at compile time. Therefore, the developer would have to choose which method should be called, instead of allowing the system to do it.

Architecture Centric

The underlying architecture of the evolving system drives the specification, construction and documentation of the system.

Use Case Driven

The use cases are the primary modeling tool employed to define the behavior of the system.

Structure Diagrams

Used for representing the data and static relationships that are in an information system.

Inheritance

Used to identify higher level, or more general, classes of objects.

Object-Oriented Approach

Views a system as a collection of self-contained objects, including both data and processes.