SOFTWARE ENGINEERINGAssignment

PREPARED By: Hamna Shahzad

SOFTWARE ENGINEERING

DATA FLOW DIAGRANDFD

graphical representation of the "flow" of data through an information system, modeling its process aspects.

used as a preliminary step to create an overview of the system, which can later be elaborated.

also be used for the visualization of structured design.

shows what kind of information will be input to and output from the system.

DATA FLOW DIAGRAM (DFD)

where the data will come from and go to. where the data will be stored. It does not show information about the timing of

process or information about whether processes will operate in sequence or in parallel.

also known as “bubble charts”. Drawn by the “Mac Draw” It show flow of data.

CONT…

Top-Down ApproachThe system designer makes "a context level DFD" or Level 0, which shows the data flows between "the system" (represented by one process) and "the system environment" (represented by terminator). system is decomposed in lower-level DFD into a set of

processes, data stores, and the data flows between these processes and data stores".

Each process is then decomposed into an "even-lower-level diagram containing its sub processes".

virtually designable diagram that technically or diagrammatically describes the inflow and outflow of data or information that is provided by the external entity.

DEVELOPING A DATA-FLOW DIAGRAM

Event Partitioning Approach:The list of all events is made.For each event a process is constructed.Each process is linked (with incoming data flows) directly

with other processes or via data stores, so that it has enough information to respond to a given event.

The reaction of each process to a given event is modeled

by an outgoing data flow. (newton 3rd law)

DEVELOPING A DATA-FLOW DIAGRAM

Process Notations. A process transforms incoming data flow into outgoing data flow.

Data store Notations. Data stores are repositories of data in the system. They are sometimes also referred to as files.

DATA FLOW DIAGRAMS NOTATIONS

Dataflow Notations. Data flows are pipelines through which packets of information flow. Label the arrows with the name of the data that moves through it. External Entity Notations. External entities are objects

outside the system, with which the system communicates. External entities are sources and destinations of the system's inputs and outputs.

DATA FLOW DIAGRAMS NOTATIONS

EXAMPLE

EXAMPLE: BUS GARAGE CONTEXT

DIAGRAM

Bus

Mechanic

Helper Bus Repair ProcessSystem

Supervisor

Accounting

Mechanical problem to be repaired

Labor

Labor

Fixed mechanical problems

Inventory Management

System

Repair summary

List of parts used

Labor, parts cost details

SEQUENCE DIAGRAMSD

A Sequence diagram in Unified Modeling Language is an interaction diagram that shows how objects operate with one another and in what order. It is a construct of a message sequence chart.

A sequence diagram shows object interactions arranged in time sequence.

A sequence diagram is a good way to visualize and validate various runtime scenarios.

Sequence diagrams are sometimes called “Event-trace diagrams”, “event scenarios”, and “timing diagrams”.

SEQUENCE DIAGRAM

Class Roles or Participants:Class roles describe the way an object will behave in context. Use the UML object symbol to illustrate class roles, but don't list object attributes.

Activation or Execution Occurrence:Activation boxes represent the time an object needs to complete a task. When an object is busy executing a process or waiting for a reply message, use a thin gray rectangle placed vertically on its lifeline.

BASIC SEQUENCE DIAGRAM SYMBOLS

AND NOTATIONS

Messages:Messages are arrows that represent communication between objects. Usehalf-arrowed lines to represent asynchronous messages. Asynchronous messages are sent from an object that will not wait for a response from the receiver before continuing its tasks.

BASIC SEQUENCE DIAGRAM SYMBOLS

AND NOTATIONS

Lifelines:Lifelines are vertical dashed lines that indicate the object's presence over time.

BASIC SEQUENCE DIAGRAM SYMBOLS

AND NOTATIONS

EXAMPLE

It Show the functionality of the system.

It focus on flow of data. Describe the path of data

from external and internal source.

Does not show iterations explicitly.

Sequence is a behavioural modelling diagram.

Sequence diagrams indicates the sequence of flow of data.

Sequence diagram not show the complex logics.

Show iterations explicitly.

DFD SD

DIFFERENCE B/W DFD AND SD

Synchronous MessageA synchronous message requires a response before the interaction can continue. It's usually drawn using a line with a solid arrowhead pointing from one object to another.

Asynchronous MessageAsynchronous messages don't need a reply for interaction to continue. Like synchronous messages, they are drawn with an arrow connecting two lifelines; however, the arrowhead is usually open and there's no return message depicted.

TYPES OF MESSAGES IN SEQUENCE

DIAGRAMS

Reply or Return MessageA reply message is drawn with a dotted line and an open arrowhead pointing back to the original lifeline.

Self MessageA message an object sends to itself, usually shown as a U shaped arrow pointing back to itself.

TYPES OF MESSAGES IN SEQUENCE

DIAGRAMS

Create MessageThis is a message that creates a new object.

Similar to a return message, it's depicted with a dashed line and an open arrowhead that points to the rectangle representing the object created. Delete Message

This is a message that destroys an object. It can be shown by an arrow with an x at the end.

TYPES OF MESSAGES IN SEQUENCE

DIAGRAMS

Found MessageA message sent from an unknown recipient, shown by an arrow from an endpoint to a lifeline.

Lost MessageA message sent to an unknown recipient. It's shown by an arrow going from a lifeline to an endpoint, a filled circle or an x.

TYPES OF MESSAGES IN SEQUENCE

DIAGRAMS

THANK YOUFor Listening