Structured Development
Transcript of Structured Development
-
8/14/2019 Structured Development
1/43
Structured
Systems Analysis
-
8/14/2019 Structured Development
2/43
-
8/14/2019 Structured Development
3/43
-
8/14/2019 Structured Development
4/43
-
8/14/2019 Structured Development
5/43
Managing Requirements
Text requirements can be extractedfrom diagrams.
The diagram structure can also beused to organize text requirements.
Be sure to create traceability fromdiagrams to text requirements
-
8/14/2019 Structured Development
6/43
Data flow diagrams
Depict the flow of data and itstransformation. Throughdecomposition, greater detail is
revealed and documented in layers ofDFDs.
A numbering system is used to
hierarchically relate the processlayers.
Data stores are also numbered so theycan be traced to data models.
There are four diagram components:
-
8/14/2019 Structured Development
7/43
Processes
have at least one input and oneoutput.
The process is usually symbolized by
a "bubble" or similar figure. The process is what transforms the
data. Functional primitives are at
the lowest level of the DFDs andcan be decomposed no further. Youknow you have gone past thefunctional primitive when the result
sounds like program logic (if, then;
-
8/14/2019 Structured Development
8/43
Data stores
are used to represent data structuresor logical data files. They areoften represented as open-ended
shapes.
-
8/14/2019 Structured Development
9/43
External entities
Represent interfaces external to thesystem. These are oftenrepresented as a small shape, such
as a diamond. Eg Suppliers, Customers
-
8/14/2019 Structured Development
10/43
Data flows
represent the exchange of databetween processes, processes anddata stores, and processes and
external entities. The direction of the data flow defines
how data flows through the system.
Data flow direction is represented byarrows.
-
8/14/2019 Structured Development
11/43
dataflow diagram
one of the three major graphicalmodeling tools of structuredanalysis:
The dataflow diagram is a modelingtool that allows us topicture asystem as a network of
functional processes, connectedto one another by pipelines andholding tanks of data.
-
8/14/2019 Structured Development
12/43
synonyms for dataflowdiagram:
Bubble chart
DFD
Bubble diagram Process model (or business process
model)
A picture of whats going on aroundhere
-
8/14/2019 Structured Development
13/43
The dataflow diagram
one of the most commonly usedsystems-modeling tools, particularlyfor operational systems in which thefunctions of the system are ofparamount importance and morecomplex than the data that thesystem manipulates.
Notation had been borrowed fromearlier papers on graph theory, andit continues to be used as aconvenient notation by software
engineers concerned with directim lementation ofmodels of user
-
8/14/2019 Structured Development
14/43
-
8/14/2019 Structured Development
15/43
-
8/14/2019 Structured Development
16/43
In the above example .
all the requirements belong under theparent 1.4.3.3: The system shallprocesspayment returns and
adjustments (in a separate DFD, notshown).
The parent is compound and should be
reworded. However, if you have limited resources,
focus on the functional primitivesbecause they are critical to the
subsequent development phases.
-
8/14/2019 Structured Development
17/43
In backward traceability, if all thechildren are satisfied, thecompound parent will be satisfied--
if all of the parent is planned forimplementation at the same timeduring the project.
If it is not, you will have traceabilityproblems.
-
8/14/2019 Structured Development
18/43
Structured Analysis
-
8/14/2019 Structured Development
19/43
Tom deMarco
-
8/14/2019 Structured Development
20/43
Data Flow Modeling
This is the process ofidentifying,modeling and documenting howdata moves aroundan information
system.
Data Flow Modeling examinesprocesses (activities that transform
data from one form to another), datastores (the holding areas for data),external entities (what sends datainto a system or receives data from a
system), and data flows (routes by
Analysis of the current
-
8/14/2019 Structured Development
21/43
Analysis of the currentsystem
Also known as: feasibility stage.
Analyze the current situation at ahigh level.
A Data Flow Diagram (DFD) is usedto describe how the current systemworks and to visualize known
problems.
http://en.wikipedia.org/wiki/Data_Flow_Diagramhttp://en.wikipedia.org/wiki/Data_Flow_Diagram -
8/14/2019 Structured Development
22/43
Investigate currentprocessing
It investigates the information flowassociated with the servicescurrently provided, and describes
them in the form of Data FlowModel.
At this point, the Data Flow
Model represents the currentservices with all theirdeficiencies.
No attempt is made to incorporate
-
8/14/2019 Structured Development
23/43
-
8/14/2019 Structured Development
24/43
-
8/14/2019 Structured Development
25/43
Appropriate ProcessName
-
8/14/2019 Structured Development
26/43
-
8/14/2019 Structured Development
27/43
Data Store
-
8/14/2019 Structured Development
28/43
External Entity
-
8/14/2019 Structured Development
29/43
Process Names
CALCULATE MISSILE TRAJECTORY
PRODUCE INVENTORY REPORT VALIDATE PHONE NUMBER
ASSIGN STUDENTS TO CLASS
-
8/14/2019 Structured Development
30/43
Process Names ?
DO STUFF
MISCELLANEOUS FUNCTIONS
NON-MISCELLANEOUS FUNCTIONS
HANDLE INPUT
TAKE CARE OF CUSTOMERS
PROCESS DATA GENERAL EDIT
-
8/14/2019 Structured Development
31/43
Process Names to avoid
DO STUFF
MISCELLANEOUS FUNCTIONS
NON-MISCELLANEOUS FUNCTIONS
HANDLE INPUT
TAKE CARE OF CUSTOMERS
PROCESS DATA GENERAL EDIT
-
8/14/2019 Structured Development
32/43
-
8/14/2019 Structured Development
33/43
-
8/14/2019 Structured Development
34/43
Logical Data Modeling
This is the process ofidentifying,modeling and documenting thedata requirements of the system
being designed.
The data are separated into entities
(things about which a businessneeds to record information) andrelationships (the associations
between the entities).
-
8/14/2019 Structured Development
35/43
-
8/14/2019 Structured Development
36/43
Entity RelationshipDiagram
Entity Relationship Diagram is aspecialized graphic that illustrates
the interrelationships betweenentities in a database.
i l i hi
-
8/14/2019 Structured Development
37/43
Entity RelationshipDiagram
| One-to-one Relationship ]
[ One-to-many Relationship
| Many-to-many Relationship
http://www.visual-paradigm.com/VPGallery/datamodeling/OneToOneRelationship.htmlhttp://www.visual-paradigm.com/VPGallery/datamodeling/OneToManyRelationship.htmlhttp://www.visual-paradigm.com/VPGallery/datamodeling/ManyToManyRelationship.htmlhttp://www.visual-paradigm.com/VPGallery/datamodeling/ManyToManyRelationship.htmlhttp://www.visual-paradigm.com/VPGallery/datamodeling/OneToManyRelationship.htmlhttp://www.visual-paradigm.com/VPGallery/datamodeling/OneToOneRelationship.html -
8/14/2019 Structured Development
38/43
-
8/14/2019 Structured Development
39/43
-
8/14/2019 Structured Development
40/43
-
8/14/2019 Structured Development
41/43
-
8/14/2019 Structured Development
42/43
Flowchart vs. Data FlowDiagram (DFD)
My employer asked me to create a flowchart inthe submission of list of on-going classes(LOGC). I decided to use a data flow diagram(DFD) instead of a flowchart. When I presentedmy work, she liked my diagram but she
preferred a flowchart rather than a DFD.I thought it was just a communication problem.However, I realized that using a DFD indescribing processes was easier to
understandcompared to flowcharts.What do you think? Are flowcharts obsolete?Posted: 07/09/2008 @ 06:05 AM (PDT) TechRepublic Blog
l h diff f
-
8/14/2019 Structured Development
43/43
Flowchart differs from DataFlow Diagram -
Flowchart: using it when you want todescribe steps of process done insequence.
Data Flow Diagram: using it when youwant to describe the relations andprocess between data, actions.
So Flowchart and DFD have differentmeaning and used in different ways.
Posted: 07/23/2008 @ 06:39 AM (PDT)