1 chapter 6-7 analysis modeling adapted by dan fleck from: - roger pressman’s slides - - jochen

1 Chapter 6-7 Analysis Modeling Adapted by Dan Fleck from: - Roger Pressmans Slides - http://www.informatics.sussex.ac.uk/users/lb203/se/SE04.pdf - Jochen Ricks 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 Braunsteinhttp://www.informatics.sussex.ac.uk/users/lb203/se/SE04.pdfhttp://webfuse.cqu.edu.au/Courses/aut2001/95169/ Coming up: Requirements Analysis

Earlier Talked about requirements Frequently in written form Supplemented by other analyses 2

Requirements Analysis Results in models: Scenario-based models (from POV of actors) Data models (information domain for the problem) Class-oriented models Flow-oriented models Behavioral models (how the software behaves according to external events) 3

4 Analysis Phase: What is it? Three objectives of requirements: 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 Three objectives of requirements: 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: Elements of the Analysis Model Software, hardware, data, human elements Software application architecture, user interface, component-level structure

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

6 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 ClassesCriteria

7 Selecting ClassesCriteria 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 were doing analysis modeling!) retained information information about it must be remembered Coming up: Selecting ClassesExample

8 Selecting ClassesExample needed services multiple attributes common attributes common operations essential requirements retained information Coming up: CRC Cards ATMUser Yes PinNum Yes No Yes Maybe Yes

CRC Cards Is there a better way to find classes? Sure Class Responsibility Collaborator Cards (see CRC slides and book pg 173) Coming up: Elements of the Analysis Model 9

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

11 The ERD: An Example places Customer request for service generates workorder worktasks materials consistsof lists (1,1) selectedfrom standard task table Coming up: Data Modeling

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

13 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) eachinstance 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 themselves data items What are some typical data objects? Coming up: Typical Data Objects

14 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 make model model body type body type price price options code options code How do data objects differ from OO classes or do they? Coming up: What is a Relationship?

15 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: Crows Foot Style ERD

16 Crows Foot Style ERD Coming up: ERD Example: From http://www.b2ttraining.com The ERD: Other styles exist. There are a few, but most are more confusing and less common than Crows foot. Depending on who you ask this was invented by Dr. Gordon Everest or Clive Finkelstein. Teacher Class Student Address 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 (addresses may not be associated with multiple students) First thing denotes optional or mandatory. Second thing denotes cardinality (one or many)

17 Coming up: Elements of the Analysis Model ERD Example: From http://www.b2ttraining.com

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

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

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

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

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

23 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

24 Data Flow Data flows through a system, beginning as input and be transformed into output. computetrianglearea base height area Coming up: Data Stores Key thought: In a DFD the DATA is what is moving on the arrows!

25 Data Stores Data is often stored for later use. look-upsensordata sensor # report required sensor #, type, location, age sensor data sensor number type, location, age Coming up: Data Flow Diagramming: Guidelines In a real system what things are Data Stores?

26 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 ensure that you show DATA moving through the system (not control) Coming up: Constructing a DFDI

27 Constructing a DFDI 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

28 Level 0 DFD Examples user processingrequest videosource NTSC video signal digitalvideoprocessor requestedvideosignal monitor Coming up: Constructing a DFDII

29 Constructing a DFDII 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

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

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

32 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: DFD Example

DFD Example Example from http://ldtconsultinginc.com/ http://ldtconsultinginc.com/ Can we add labels to unlabled data flows? Is this a level 0 diagram? Coming up: Lets Try It 33

Lets Try It Lets create a DFD for A carpet cleaning business A web-based order processing system for a computer store An address book for an iPhone Coming up: Flow Modeling Notes 34

35 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) The things that move on the arrows are DATA! Coming up: Elements of the Analysis Model

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

37 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

38 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 What are some states for an ATM machine? Washing machine? Cell phone? Coming up: State Diagram for the ControlPanel Class

39 State Diagram for the ControlPanel Class Coming up: State Diagram Details

State Diagram Details Coming up: The States of a System 40 State Name (verb in current tense) (Optional) actions happening during state Name Examples: sorting validating updating status [age > 20] [age

1 chapter 6-7 analysis modeling adapted by dan fleck from: - roger pressman’s slides - - jochen

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