Requirement Analysis

1
Requirement Analysis
CEN 4010 Class 10 09/29

• Review of Class 9
• Overview of Analysis
• Analysis Concepts
• From Use Cases to Objects

2
Overview of Analysis

• Analysis focuses on producing a model (analysis
  model) of the system that is correct, complete,
  consistent, and verifiable.
• The analysis model is composed of three
  individual models
• Functional model represented by use cases and
  scenarios.
• Analysis object model represented by class and
  object diagrams.
• Dynamic model represented by state charts and
  sequence diagrams.

3
Overview of Analysis cont

• Focuses on structuring and formalizing the
  requirements elicited from users.
• This formalization leads to new insights and the
  discovery of errors in the requirements.
• The requirements specifications is updated to
  reflect insights gained during analysis, then
  review the changes with the client and the users.
• Translating a requirements spec into a formal or
  semiformal model forces developers to identify
  and resolve difficult issues early in the
  development.

4
Overview of Analysis cont
UML activity diagram the products of
requirements elicitation and analysis. Fig 5-2 P.
175
Requirements Elicitation
Requirements Specification
nonfunctional requirements
functional model
Analysis
Analysis model
dynamic model
analysis object model
System Design
Object Design
5
Analysis concepts Types of Objects

• The analysis object model contains entity,
  boundary, and control objects.
• Entity objects - persistent information tracked
  by the system.
• Boundary objects - interactions between the
  actors and the system.
• Control objects - tasks that are performed by the
  user and supported by the system.

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Types of objects cont

• UML provides the stereotype mechanism that
  enables the developer to attach meta information
  to modeling elements. E.g., ltltcontrolgtgt
• Naming conventions can also be used to identify
  the different types of objects in the analysis
  model, e.g., InputControl, ButtonBoundary.

ltltentitygtgt Employee
7
Types of objects cont

• Example 5.6 Q1. Consider a file system with a
  graphical user interface, such as Macs Finder,
  Windows Explorer, or Linuxs KDE. The following
  objects were identified from a use case
  describing how to copy a file from a floppy disk
  to a hard disk File, Icon, TrashCan, Folder,
  Disk, Pointer. Specify which are entity objects,
  which are boundary objects, and which are control
  objects.

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Types of objects cont

• Entity objects File, Folder, Disk
• Boundary objects Icon, Pointer, TrashCan
• Control objects none in this example.
• Example 5.6 Q2. Assuming the same file system as
  before, consider a scenario consisting of
  selecting a file on a floppy, dragging it to a
  folder and releasing the mouse. Identify and
  define at least one control object associated
  with this scenario.

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Types of objects cont

• The purpose of a control object is to encapsulate
  the behavior associated with a user level
  transaction. In this example, we identify a
  CopyFile control object, which is responsible for
  remembering the path of the original file, the
  path of the destination folder, checking if the
  file can be copied (access control and disk
  space), and to initiate the file copying.

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Analysis concepts - Association

• Recall one of the adornments that apply to
  associations is multiplicity.
• Multiplicity indicates the number of links that
  can legitimately originate from an instance of
  the class to the association end. Types of
  multiplicity
• one-to-one has multiplicity 1 on each end.
• one-to-many has a multiplicity a on one end and
  0..n (or ) or 1..n on the other.
• many-to-many has multiplicity 0..n or 1..n on
  both ends.

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Association Examples
one-to-one
1
1
is issued
Student
FIU_IDCard
one-to-many
1
1..
employs
College
Professor
many-to-many
1..
1..
takes
Student
Course
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Analysis concepts - Generalization

• Generalization enables us to organize concepts
  into hierarchies. (is-a relationship).
• At the top of the hierarchy is the general
  concept (e.g., Student), and at the bottom of the
  hierarchy are the most specialized (e.g.,
  Graduate, Undergraduate).
• Note, inheritance (in OOP) is the mechanism by
  which more-specific elements incorporate the
  structure an behavior of more-general elements.
  (Booch et al.)

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Generalization cont
Student
Each project should have at least one
generalization in the class design.
ssn string name string
getName() string getSSN() string
Graduate
Undergraduate
UGDegree string
year String
getYear() String
getUGDeg() string
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From Use Cases to Objects

• Participating objects form the basis of the
  analysis model.
• Participating objects are identified by examining
  each of the use cases developed during
  requirements elicitation.
• Using the natural language description of the use
  cases and an intuitive set heuristics, objects
  can be identified. (Abbot 83)
• See table on the next slide

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From Use Cases to Objects cont
Part of speech Model component Examples
Proper noun Object Peter
Common noun Class Faculty
Doing verb Operation Teaches, grades
Being verb Inheritance Is a kind of, is one of either
Having verb Aggregation Has, consist of, includes
Modal verb Constraints Must be
Adjective Attribute SSN, Office ,
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From Use Cases to Objects cont

• Heuristics for identifying objects
• terms the developers or users need to clarify in
  the use cases.
• recurring nouns in the use cases.
• real-world entities that the system needs to keep
  track of.
• real-world activities the system needs to keep
  track of.
• data sources and sinks
• always use the users term.

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From Use Cases to Objects cont

• Adv. of using natural language
• focuses on users terms.
• developers become familiar with domain jargon.
• Disadv. of using natural language
• depends on writing style.
• natural language is imprecise and ambiguous.
• In use case there are usually more nouns than
  relevant classes.

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From Use Cases to Objects cont

• Entity objects are most common e.g., Student,
  Professor, Course.
• Boundary objects represent the system interface
  with the actors (people or other systems).
• Heuristics
• Identify forms and windows the user needs to
  enter data into the system.
• Identify notices and messages the system uses to
  respond to the user.
• Always use the terms of the user not impl.
  technology.

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From Use Cases to Objects cont

• Control objects are responsible for coordinating
  boundary and entity objects.
• Heuristics
• Identify one control object per use case. If
  more than one control object is required then the
  use case might be too long.
• Identify one control object per actor in the use
  case.
• The life span of a control object should be the
  extent of the user session. Beginning and end of
  the control object activation should be easily
  identified.

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Review Topics for Exam 1

1. Definitions software engineering, role,
   activity, task, milestone, deliverable, notation,
   method, methodology, use cases, actors.
2. Software process.
3. Attributes of good software.
4. Software process models. Advantages and
   disadvantages of the software process models.
   Review diagrams for Waterfall, Boehms Spiral,
   Incremental Development, and Unified Software
   Process.
5. UML Types of diagrams and relationships, with
   examples.

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Review Topics for Exam 1

• Software Project management
• charts to develop schedules
• focus on how it applies to your project e.g.,
  tasks, organization,
• Requirements elicitation
• Activities
• Functional and non-functional constraints
• The format of a use case given in class.
  Identification of use cases for your team project
  based on decision support.
• Requirements reviews

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Review Topics for Exam 1

• Analysis model
• Components of the analysis model
• Purpose of the analysis model.
• Questions on Project