Chapter 8 Analysis Modeling Adapted by Dan Fleck from: - Roger Pressman’s Slides - http://www.informatics.sussex.ac.uk/users/lb203/se/SE04.pdf - Jochen Rick’s slides from GA Institute of Technology - http://webfuse.cqu.edu.au/Courses/aut2001/95169/ Extra_Examples/DFD_Example_1/ - System Analysis and Design slides edited by Yale Braunstein Coming up: Requirements Analysis

Requirements Analysis specifies software’s operational characteristics indicates software's interface with other system elements establishes constraints that software must meet Requirements analysis allows the software engineer (called an analyst or modeler in this role) to: elaborate on basic requirements established during earlier requirement engineering tasks build models that depict user scenarios, functional activities, problem classes and their relationships, system and class behavior, and the flow of data as it is transformed. Coming up: Analysis Phase: What is it?

Analysis Phase: What is it? Three objectives: To describe what the customer requires To establish a basis for the creation of a software design To define a set of requirements that can be validated once the software is built Coming up: Analysis Modeling Approaches

Analysis Modeling Approaches Structural analysis: The data: The model defines their attributes and relationships. The processes that transform the data: The model shows how they transform the data objects as they flow through the system. Object-oriented analysis: Focus: Classes and their inter-relationships UML is predominantly object-oriented Entity Relationship Model - ERD Flow = Data Flow Diagram But don’t be to dogmatic! Coming up: Elements of the Analysis Model

Elements of the Analysis Model Scenario-based elements Flow-oriented elements Use-case diagrams Use cases - text Activity Diagrams Swim lane diagrams Data-flow diagrams Control flow diagrams Processing narratives Analysis Model Class-based elements Behavioral elements Class diagrams Analysis Packages CRC Models Collaboration Diagrams State diagrams Sequence diagrams ER Diagrams Coming up: Elements of the Analysis Model

Elements of the Analysis Model Scenario-based elements High level idea of the system from user’s or a functional perspective Flow-oriented elements How information flows throughout the system (data and control flow) Behavioral elements How the system responds to external stimuli Class-based elements Static view of the system and how the different parts are related. Tries to show standard ideas of object oriented development Coming up: Class-Based Modeling

Class-Based Modeling Identify analysis classes by examining the problem statement Use a “grammatical parse” to isolate potential classes Identify the attributes of each class Identify operations that manipulate the attributes Coming up: Domain Analysis

Domain Analysis Software domain analysis is the identification, analysis, and specification of common requirements from a specific application domain, typically for reuse on multiple projects within that application domain . . . What is object oriented domain analysis then? Coming up: Domain Analysis

Domain Analysis Software domain analysis is the identification, analysis, and specification of common requirements from a specific application domain, typically for reuse on multiple projects within that application domain . . . Object-oriented domain analysis is the identification, analysis, and specification of common, reusable capabilities within a specific application domain, in terms of common objects, classes, subassemblies, and frameworks . . . Coming up: Grammatical Parsing Donald Firesmith

Grammatical Parsing Write an informal description of the problem. The customer requirements document is one such description. Underline all nouns in the description Decide which of these are really objects which the project requires and organize them in related clusters Nouns are your classes Verbs are your methods Got here 2/27/2008 Coming up: Grammatical Parsing

Grammatical Parsing University Bank will be opening in Oxford, Mississippi, in January, 2000. We plan to use a full service automated teller machine (ATM) system.The ATM system will interact with the customer through a display screen, numeric and special input keys, a bankcard reader, a deposit slot, and a receipt printer.Customers may make deposits, withdrawals, and balance inquires using the ATM machine, but the update to accounts will be handled through an interface to the Accounts system.Customers will be assigned a Personal Identification Number (PIN) and clearance level by the Security system. The PIN can be verified prior to any transaction.In the future, we would also like to support routine operations such as a change of address or phone number using the ATM Nouns are your classes Verbs are your methods Coming up: Grammatical Parsing

Grammatical Parsing University Bank will be opening in Oxford, Mississippi, in January, 2000. We plan to use a full service automated teller machine (ATM) system.The ATM system will interact with the customer through a display screen, numeric and special input keys, a bankcard reader, a deposit slot, and a receipt printer.Customers may make deposits, withdrawals, and balance inquires using the ATM machine, but the update to accounts will be handled through an interface to the Accounts system.Customers will be assigned a Personal Identification Number (PIN) and clearance level by the Security system. The PIN can be verified prior to any transaction.In the future, we would also like to support routine operations such as a change of address or phone number using the ATM Nouns are your classes Verbs are your methods Coming up: Typical Classes (a reminder)

Typical Classes (a reminder) External entities - printer, user, sensor Things - reports, displays, signals Occurrences or events (e.g., interrupt, alarm) Roles (e.g., manager, engineer, salesperson) Organizational units (e.g., division, team) Places (e.g., manufacturing floor or loading dock) Structures (e.g., sensors, four-wheeled vehicles, or computers) But, how do we select classes? Coming up: Selecting Classes—Criteria

Selecting Classes—Criteria retained information – information about it must be remembered needed services – operations that change the attributes multiple attributes – if it is only one attribute, probably should be part of another class common attributes – common things for all instances of a class common operations – for all instances of the class essential requirements – appear in the PROBLEM space (remember we’re doing analysis modeling!) select a noun as a class if it fits all (or most) of these criteria (in the analysis phase) Coming up: Selecting Classes—Example

Selecting Classes—Example ATMUser Yes PinNum Yes No Maybe retained information needed services multiple attributes common attributes common operations essential requirements Coming up: Elements of the Analysis Model

Elements of the Analysis Model Scenario-based elements Flow-oriented elements Use-case diagrams Use cases - text Activity Diagrams Swim lane diagrams Data-flow diagrams Control flow diagrams Processing narratives Analysis Model Class-based elements Behavioral elements Class diagrams Analysis Packages CRC Models Collaboration Diagrams State diagrams Sequence diagrams Coming up: Activity Diagram

Activity Diagram Supplements the use-case by providing a diagrammatic representation of procedural flow How might we make this better? Coming up: Swimlane Diagrams

Swimlane Diagrams Allows the modeler to represent the flow of activities described by the use-case and at the same time indicate which actor (if there are multiple actors involved in a specific use-case) or analysis class has responsibility for the action described by an activity rectangle Coming up: Activity Diagram Example

Activity Diagram Example To show concurrent activity, activity diagrams allow branches and joins. You can also reference or include other activity diagrams Got here Class -- Sept 30th 2008 Coming up: Lets Try It

Lets Try It Lets create a swimlane activity diagram for opening a Lemonade stand. Let’s create a swimlane diagram to apply for and get a job when you graduate. Let’s create a swimlane diagram for withdrawing money from an ATM. Coming up:

END OF MIDTERM MATERIAL Coming up: Data Modeling

Data Modeling examines data objects independently of processing focuses attention on the data domain creates a model at the customer’s level of abstraction indicates how data objects relate to one another Coming up: What is a Data Object?

What is a Data Object? Object —something that is described by a set of attributes (data items) and that will be manipulated within the software (system) each instance of an object (e.g., a book) can be identified uniquely (e.g., ISBN #) each plays a necessary role in the system i.e., the system could not function without access to instances of the object each is described by attributes that are Data Object is similar to a class, but with no methods themselves data items What are some typical data objects? Coming up: Typical Data Objects

Typical Data Objects external entities (printer, user, sensor) things (e.g, reports, displays, signals) occurrences or events (e.g., interrupt, alarm) roles (e.g., manager, engineer, salesperson) organizational units (e.g., division, team) places (e.g., manufacturing floor) structures (e.g., employee record) External - produces or consumes information Anything that consolidates multiple pieces of data (attributes) Coming up: Data Objects and Attributes

Data Objects and Attributes A data object contains a set of attributes that act as an aspect, quality, characteristic, or descriptor of the object object: automobile attributes: make model body type price options code How do data objects differ from OO classes or do they? Coming up: What is a Relationship?

What is a Relationship? relationship —indicates “connectedness”; a "fact" that must be "remembered" by the system and cannot or is not computed or derived mechanically several instances of a relationship can exist objects can be related in many different ways Coming up: ERD Notation

ERD Notation One common form: object object Another common form: relationship object 1 2 (1, 1) attribute Another common form: object relationship object 1 2 (0, m) (1, 1) 0 to many one and only one (mandatory) See http://www.smartdraw.com/tutorials/software/erd/tutorial_01.htm for a tutorial on how to draw entity relationship diagrams. Coming up: The ERD: An Example

The ERD: An Example request Customer for service (1,1) (1,m) (1,1) places (1,1) (1,m) (1,1) standard task table (1,n) work order generates (1,1) (1,1) (1,1) work tasks (1,w) selected from consists of (1,w) (1,i) materials lists This is in a very rare “Martin Style” (or possibly an error’d Chen style) See http://www.smartdraw.com/tutorials/software/erd/tutorial_01.htm Coming up: Bachman Style ERD

Bachman Style ERD The ERD: Chen Style is very confusing, and there are many examples on the web with the cardinality and optionality in different places. To avoid confusion we’ll use the more populare Bachman (Crow’s foot) notation. Teacher teaches 0 to many classes Classes have 1 and only 1 teacher Students have 1 to many addresses An address is for zero to one student (addresse may not be associated with students) Teacher Class Student Address First “thing” denotes optional or mandatory. Second “thing” denotes cardinality (one or many) Coming up: The ERD: An Example

The ERD: An Example request Customer for service standard work places request for service Customer standard task table generates work order (1,1) selected from work tasks consists of materials lists This is in Bachman or Crow’s feet style. This is the style I expect you to know. Forget about Chen  Coming up: Elements of the Analysis Model

Elements of the Analysis Model Scenario-based elements Onward to data flow diagrams! Flow-oriented elements Use-case diagrams Use cases - text Activity Diagrams Swim lane diagrams Data-flow diagrams Control flow diagrams Processing narratives Analysis Model Class-based elements Behavioral elements Class diagrams Analysis Packages CRC Models Collaboration Diagrams State diagrams Sequence diagrams Coming up: Flow-Oriented Modeling

Flow-Oriented Modeling Represents how data objects are transformed at they move through the system A data flow diagram (DFD) is the diagrammatic form that is used Considered by many to be an ‘old school’ approach, flow-oriented modeling continues to provide a view of the system that is unique—it should be used to supplement other analysis model elements Coming up: The Flow Model

The Flow Model Every computer-based system is an information transform .... computer based system input output Coming up: Flow Modeling Notation

Flow Modeling Notation external entity process data flow data store Coming up: External Entity

External Entity A producer or consumer of data Examples: a person, a device, a sensor Another example: computer-based system Data must always originate somewhere and must always be sent to something Coming up: Process

Process A data transformer (changes input to output) Examples: compute taxes, determine area, format report, display graph Data must always be processed in some way to achieve system function Coming up: Data Flow

Data Flow Data flows through a system, beginning as input and be transformed into output. base compute triangle area area height Coming up: Data Stores

Data Stores Data is often stored for later use. look-up sensor data sensor #, type, location, age look-up sensor data report required type, location, age sensor number sensor data Coming up: Data Flow Diagramming: Guidelines

Data Flow Diagramming: Guidelines all icons must be labeled with meaningful names the DFD evolves through a number of levels of detail always begin with a context level diagram (also called level 0) always show external entities at level 0 always label data flow arrows do not represent procedural logic Coming up: Constructing a DFD—I

Constructing a DFD—I review the data model to isolate data objects and use a grammatical parse to determine “operations” determine external entities (producers and consumers of data) create a level 0 DFD Coming up: Level 0 DFD Examples

Level 0 DFD Examples user digital video processor monitor video source processing request user requested video signal digital video processor monitor video source NTSC video signal Coming up: Constructing a DFD—II

Constructing a DFD—II write a narrative describing the transform parse to determine next level transforms “balance” the flow to maintain data flow continuity develop a level 1 DFD use a 1:5 (approx.) expansion ratio Coming up: The Data Flow Hierarchy

The Data Flow Hierarchy b x P y level 0 c a p2 f p1 b p4 d 5 g p3 e level 1 Coming up: Example DFD: Level 1

Example DFD: Level 1 Coming up: DFD: A practical example

DFD: A practical example Launched Dec. 11, 1998, the Climate Orbiter plunged too steeply into the Martian atmosphere Sept. 23, 1999, and either burned up or crashed. In an initial failure report released Oct. 15, 2000 the review board blamed the navigation error on a communications foul-up between NASA's Jet Propulsion Laboratory and prime contractor Lockheed Martin. Coming up: Flow Modeling Notes

Flow Modeling Notes each bubble is refined until it does just one thing the expansion ratio decreases as the number of levels increase most systems require between 3 and 7 levels for an adequate flow model a single data flow item (arrow) may be expanded as levels increase (data dictionary provides information) Got here 10/16/2008 Coming up: Elements of the Analysis Model

Elements of the Analysis Model Scenario-based elements Flow-oriented elements Use-case diagrams Use cases - text Activity Diagrams Swim lane diagrams Data-flow diagrams Control flow diagrams Processing narratives Analysis Model Oh behave! Class-based elements Behavioral elements Class diagrams Analysis Packages CRC Models Collaboration Diagrams State diagrams Sequence diagrams Coming up: Behavioral Modeling

Behavioral Modeling The behavioral model indicates how software will respond to external events or stimuli. To create the model, the analyst must perform the following steps: Evaluate all use-cases to fully understand the sequence of interaction within the system. Identify events that drive the interaction sequence and understand how these events relate to specific objects. Create a sequence diagram for each use-case. Build a state diagram for the system. Review the behavioral model to verify accuracy and consistency. Coming up: State Representations

State Representations In the context of behavioral modeling, two different characterizations of states must be considered: the state of each class as the system performs its function and the state of the system as observed from the outside as the system performs its function The state of a class takes on both passive and active characteristics [CHA93]. A passive state is simply the current status of all of an object’s attributes. The active state of an object indicates the current status of the object as it undergoes a continuing transformation or processing. Coming up: State Diagram for the ControlPanel Class

State Diagram for the ControlPanel Class Coming up: The States of a System

The States of a System state—a set of observable circumstances that characterizes the behavior of a system at a given time state transition —the movement from one state to another event —an occurrence that causes the system to exhibit some predictable form of behavior action —process that occurs as a consequence of making a transition Coming up: Behavioral Modeling

Behavioral Modeling make a list of the different states of a system (How does the system behave?) indicate how the system makes a transition from one state to another (How does the system change state?) indicate event indicate action draw a state diagram or a sequence diagram Coming up: State Diagram - Lets Try It!

State Diagram - Lets Try It! You are designing a traffic light system for this intersection. Draw a state diagram showing the different states and how they transition. North West Got here on class 10/2/2008 East South Coming up: Elements of the Analysis Model

Elements of the Analysis Model Scenario-based elements Flow-oriented elements Use-case diagrams Use cases - text Activity Diagrams Swim lane diagrams Data-flow diagrams Control flow diagrams Processing narratives Analysis Model Class-based elements Behavioral elements Class diagrams Analysis Packages CRC Models Collaboration Diagrams State diagrams Sequence diagrams Coming up: Object Oriented Analysis (OOA)

Object Oriented Analysis (OOA) The intent of OOA is to define all classes (and the relationships and behavior associated with them) that are relevant to the problem to be solved. For that, a number of tasks must occur: Classes must be identified (i.e., attributes and methods) A class hierarchy is defined Object-to-object relationships should be represented Object behavior must be modeled Tasks 1 through 4 are reapplied iteratively Coming up: Object-Oriented Concepts

Object-Oriented Concepts What are the basic object oriented concepts? Coming up: Object-Oriented Concepts

Object-Oriented Concepts What are the basic object oriented concepts? Classes and objects Attributes and operations Encapsulation and instantiation Inheritance The analysis model is designed to help you make “good” choices Coming up: Object-Oriented Concepts

Object-Oriented Concepts What helps you determine if something should be a class or an atribute? What helps you determine needed operations? How does the analysis model make sure your requirements are correct? Coming up: Elements of the Analysis Model

Elements of the Analysis Model Scenario-based elements High level idea of the system from user’s or a functional perspective Flow-oriented elements How information flows throughout the system (data and control flow) Behavioral elements How the system responds to external stimuli Class-based elements Static view of the system and how the different parts are related. Tries to show standard ideas of object oriented development Coming up: Analysis Model Rules of Thumb

Analysis Model Rules of Thumb The model should focus on requirements that are visible within the problem or business domain. The level of abstraction should be relatively high. Each element of the analysis model should add to an overall understanding of software requirements and provide insight into the information domain, function and behavior of the system. Delay consideration of infrastructure and other non-functional models until design. Minimize coupling throughout the system. Be certain that the analysis model provides value to all stakeholders. Keep the model as simple as it can be. Coming up: Writing the Software Specification

Writing the Software Specification Everyone knew exactly what had to be done until someone wrote it down! Read the last three slides on your own Coming up: Specification Guidelines

Specification Guidelines Coming up: Specification Guidelines

Specification Guidelines Coming up: Specification Guidelines

Specification Guidelines End of presentation