1. 1 Chapter 6-7 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 Braunsteinhttp://www.informatics.sussex.ac.uk/users/lb203/se/SE04.pdfhttp://webfuse.cqu.edu.au/Courses/aut2001/95169/ Coming up: Requirements Analysis

2. 2 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?

3. 3 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 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: Elements of the Analysis Model

4. 4 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

5. 5 Elements of the Analysis Model Scenario-based elements Class-based elements Flow-oriented elements Behavioral elements Coming up: Class-Based Modeling High level idea of the system from user’s or a functional perspective How information flows throughout the system (data and control flow) How the system responds to external stimuli Static view of the system and how the different parts are related. Tries to show standard ideas of object oriented development

6. 6 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: Grammatical Parsing

7. 7 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 Coming up: Grammatical Parsing

8. 8 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 Coming up: Grammatical Parsing

9. 9 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 Coming up: Typical Classes (a reminder)

10. 10 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

11. 11 Selecting Classes—Criteria 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!) retained information – information about it must be remembered Coming up: Selecting Classes—Example

12. 12 Selecting Classes—Example needed services multiple attributes common attributes common operations essential requirements retained information Coming up: CRC Cards ATMUser Yes PinNum Yes No Yes Maybe Yes

13. 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 13

14. 14 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

15. 15 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

16. 16 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?

17. 17 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

18. 18 Typical Data Objects external entities (printer, user, sensor) things (e.g, reports, displays, signals) (e.g, reports, displays, signals) occurrences or events (e.g., interrupt, alarm) roles (e.g., manager, engineer, salesperson) organizational units (e.g., division, team) (e.g., division, team) places (e.g., manufacturing floor) (e.g., manufacturing floor) structures (e.g., employee record) Coming up: Data Objects and Attributes

19. 19 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?

20. 20 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: Crow’s Foot Style ERD

21. 21 Crow’s Foot Style ERD Coming up: ERD Example: From http://www.b2ttraining.com The ERD: Other style’s exist. There are a few, but most are more confusing and less common than Crow’s 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)

22. 22 Coming up: Elements of the Analysis Model ERD Example: From http://www.b2ttraining.com

23. 23 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

24. 24 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 unique—it 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 unique—it should be used to supplement other analysis model elements Coming up: The Flow Model

25. 25 The Flow Model Every computer-based system is an information transform.... computerbasedsystem data input output Coming up: Flow Modeling Notation

26. 26 Flow Modeling Notation external entity process data flow data store Coming up: External Entity

27. 27 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

28. 28 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

29. 29 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!

30. 30 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”?

31. 31 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 DFD—I

32. 32 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

33. 33 Level 0 DFD Examples user processingrequest videosource NTSC video signal digitalvideoprocessor requestedvideosignal monitor Coming up: Constructing a DFD—II

34. 34 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

35. 35 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

36. 36 Example DFD: Level 1 Coming up: DFD: A practical example

37. 37 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

38. 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 38

39. 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 39

40. 40 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

41. 41 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

42. 42 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

43. 43 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

44. 44 State Diagram for the ControlPanel Class Coming up: State Diagram Details

45. State Diagram Details Coming up: The States of a System 45 State Name (verb in current tense) (Optional) actions happening during state Name Examples: sorting validating updating status … [age > 20] [age <= 20] Guards: Use to describe event that causes a state transition happens (ALL transitions should have guards) [age <= 20]/setFlag(false) Action: If something happens while transitioning to another state. (Optional)

46. 46 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

47. 47 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!

48. 48 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 South East West Coming up: Elements of the Analysis Model

49. 49 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: Object Oriented Analysis (OOA)

50. 50 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: 1. Classes must be identified (i.e., attributes and methods) 2. A class hierarchy is defined 3. Object-to-object relationships should be represented 4. Object behavior must be modeled 5. Tasks 1 through 4 are reapplied iteratively Coming up: Object-Oriented Concepts

51. 51 Object-Oriented Concepts What are the basic object oriented concepts? Coming up: Object-Oriented Concepts

52. 52 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

53. 53 Object-Oriented Concepts What helps you determine if something should be a class or an attribute? What helps you determine needed operations? How does the analysis model make sure your requirements are correct? Coming up: Elements of the Analysis Model

54. 54 Elements of the Analysis Model Scenario-based elements Class-based elements Flow-oriented elements Behavioral elements Coming up: Analysis Model Rules of Thumb High level idea of the system from user’s or a functional perspective How information flows throughout the system (data and control flow) How the system responds to external stimuli Static view of the system and how the different parts are related. Tries to show standard ideas of object oriented development

55. 55 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 nonfunctional 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: Analysis Phase: What is it?

56. 56 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 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: Writing the Software Specification

57. 57 Writing the Software Specification Everyone knew exactly what had to be done until someone wrote it down! Coming up: Specification Guidelines Read the last three slides on your own

58. 58 Specification Guidelines Coming up: Specification Guidelines

59. 59 Specification Guidelines Coming up: Specification Guidelines

60. 60 Specification Guidelines End of presentation