Analysis Modeling (cont’d)
CpSc 372:Introduction to Software Engineering
Jason O. [email protected]
Authorship Disclaimer. These slides are intended to serve as teaching instruments for an undergraduate course in Software Engineering. While the slides were formatted by Dr. Hallstrom, the content is compiled from other sources, including the readings listed on the course website, Dr. Pressman’s Software Engineering textbook, and various internet materials. In almost every case, the ideas belong to someone other than Dr. Hallstrom. Indeed, text is often quoted verbatim without an explicit citation (to improve the readability of the slides). The original authors retain all copyrights. If you are interested in citing any of the material in these slides, please contact Dr. Hallstrom for the original source(s). DO NOT CITE THIS PRESENTATION. THE CONTENT SHOULD NOT BE ATTRIBUTED TO DR. HALLSTROM. SEE DR. HALLSTROM IF YOU HAVE ANY QUESTIONS.
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A Roadmap
Use-cases Use-case diagrams Activity diagrams Swimlane diagrams
Data object diagrams ERD diagrams Data flow diagrams Process specifications
We are going to examine some of the key tools used for creating an analysis model.
General
Structured Analysis OO Analysis Class diagrams Packages CRC cards Sequence Diagrams
These tools are not specific to either structured analysis or OO analysis.
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Data Flow Diagrams
Models data elements Attributes Relationships
Models processes that transform data
Structured Analysis:
Data object diagrams ERD diagrams
modeled using
Data flow diagram Process narrative
modeled using
A data flow diagram describes information flow among a set of processes and actors.
A process narrative describes how a single process transforms input data to output data.
Modeling Tools:
1
*
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Data Objects
Plays a necessary role Characterized by attributes Uniquely identifiable (?)
Roles Events Places
A data object is a domain element that will be manipulated by the system.
Characteristics: Examples: External entities Structures Other things
Object: car
Attributes:• VIN #• Make• Model• Price
Modeling
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Relationships, Cardinality, Modality
Cardinality Defines the number of items
on either end of a connection
Relationships Define connections between
objects
Modality Defines the necessity of a
connection
Person
Car
ownsinsured
11
**
Trailer
attached
1
1
Entity-Relationship Diagram (ERD)
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DFD: A Basic Example
SafeHomesoftware
Controlpanel
Sensors
Paneldisplay
Alarm
Telephoneline
commandsand data
sensorstatus
displayinformation
telephonetones
alarmtype
External entities(squares)
Data flows(directed edges)
Processes(circles)
Notice that the system is represented as a single bubble.This is known as a level 0 DFD, or a context diagram.
(See Pressman Chapter 8, Section 8.6.1, pg. 195)
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DFDs and Progressive Refinement
Each DFD reveals progressively more detail than the DFD that preceded it.
Level 1 DFD:
(See Pressman Chapter 8, Section 8.6.1, pg. 196)
Interactwith user
Controlpanel
commandsand data Configure
system
Configurerequest
Activate /deactivate
system
Start/stoprequest
Processpassword
…
password …
…
Refinement continues until each bubble can be (easily) implemented as a program module.
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Process Narrative
Processpassword
password
…
…
A process specification describes all of the flow processes in the final (most detailed) DFD.
A process specification can be represented as a collection of process narratives.
“The process password transform performs password validation at the control panel for the SafeHome security function. Process password receives a four-digit password from the interact with user function. The password is first compared to the master password stored within the system …”
(See Pressman Chapter 8, Section 8.6.4, pg. 200)
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How are DFDs Constructed?
Grammaticalparse
Developprocess
narratives
Level 0 DFD
Scopedocument
Grammaticalparse
Next level DFD
(See Pressman Chapter 8, Section 8.6.1, pg. 195)
(nouns = external entities, data/control objects, data stores)(verbs = processes)
Note that nouns and verbs are associated with one another.
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Some Guidelines
Level 0 DFD should contain only a single bubble
All arrows and bubbles should be meaningfully labeled
Refinement begins by isolating next level processes, data objects, and data stores
Refine only one bubble at a time
Data flow continuity must be maintained between levels
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Let’s Try it Out!
The video library management system will interact with the user through a web-based browser interface. When the user logs into the system, the system will determine the user’s access privileges based on the user configuration database. If the user is an administrator, the system will allow the user to enter new movie titles, new actor information, etc. If the user is not an administrator, the system will allow the user to query the system based on movie title, actor, director, etc.
The Video Library Management System
What might the level 0 DFD look like? Level 1?
An excerpt from the scope document:
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And a Bit of Review
The system will allow the user to store a number of information elements with each video, director, and actor. Each video will be characterized by a title, a genre descriptor, a short synopsis, a list of directors, a list of actors, a rating, and a UPC code. Each actor and director will be characterized by a first and last name, a year of birth, and a brief biography. When the user is viewing a video entry, they will be able to retrieve the full actor (or director) information by clicking the actor’s (or director’s) name.
Another excerpt from the scope document:
What would be an appropriate ERD diagram for this excerpt?