Structured design - 1 © Minder Chen, Produce Paycheck Retrieve Employee Record Global Data Store Offpage Calling Module Called Module System Device Module Module Name Normal Procedure (Subroutine) Call Module Name Library(Predefined) Module Global Data Store Used by Page-Jones Offpage Used by Page-Jones Sender Receiver Control Flag Data Structure Chart Notations

Structured design - 2 © Minder Chen, A A,1A,2A,3 Call A,1 Call A,2 Call A,3 Sequence Structured Chart Notations A A,4A,3A,2A,1 Call A,1 IF Tx-Code = “A” Then Call A,2 ELSE IF Tx-Code = “B” Then Call A,3 ELSE IF Tx-Code =“C” THEN Call A,4 Decision A A,1A,2A,3A,4 Call A,1 Repeat Call A,2 Call A,3 Call A,4 Until EOF = “true” A A A,3 A,1 A,2 Statement X Statement T Statement Z Call A,1 Statement X Statement Y StatementZ Call A,3 Iteration Lexical Inclusion

Structured design - 3 © Minder Chen, Structured Chart Notations (Contd.) Notations used by Page-Jones Decision Iteration Lexical Inclusion (The Hat Symbol)

Structured design - 4 © Minder Chen, Structure Chart Notations Interface Table I/F# Input Output 1 A,B C 2 X Y,Z Interface Table 12 Asynchronous Activation of a Subtask Concurrent Activation Symbol Information Cluster A BC D Modules A, B, and C has exclusive access to Data D Program X Physical Packaging Boundary

Structured design - 5 © Minder Chen, Answer to Problem Enter Customer payments 2.5 Display Customer payment 2.32 Verify Customer account 2.21 Get Customer record 2.11 Key invoice remittance 2.4 write Customer payment transaction 2.3 Update A/R master 2.2 Add Customer information 2.1 Key remittance 2.33 Rewrite A/R record 2.22 Verify Customer account 2.31 Get receivable record 2.12 Key monthly statement remittance Structure chart for program 2.0. Enter customer payment Exercise - 3 Remittance EOT Customer-ID Invoice- remittance Monthly- Statement- remittance Customer- sold-to- name Remittance Customer-sold- to-name Customer- payment Customer -ID Customer- number Customer- record No-record- on-file Valid- account A/R- record Old- A/R- record New-A/R- record No-record- on-file Valid account Posting-ok

Structured design - 6 © Minder Chen, How would you partition this system?

Structured design - 7 © Minder Chen, Type of Coupling Tightness of Coupling Goodness of Design Normal Coupling Data Coupling Stamp Coupling Control Coupling Common Coupling Content Coupling Loose Tight Good Bad

Structured design - 8 © Minder Chen, Normal Coupling A. Call B. A. Call B using X,Y. BB Module A and module B are normally coupled if - A calls B - B returns to A All information passed between them are through parameter passing X X Y Y

Structured design - 9 © Minder Chen, UPDATE CUSTOMER MASTER FILE GET VALID INPUT VALIDATE CUSTOMER TRANSACTION UPDATE MASTER PUT CUSTOMER MASTER GET INPUT GET CUSTOMER MASTER GET CUSTOMER TRANS Transaction Transaction is valid Transaction Master Record Acct Number Master Record Updated Master Record Master Record Valid Trans- action Updated Master Record Valid Trans- action

Structured design - 10 © Minder Chen, Data Coupling Calculate Monthly payment of a House Calculate Mortgage Payment Mortgage PaymentLoan Amount Term Interest Rate Module A and module B are data coupled if - A calls B - B returns to A - All information passed between them are through parameter passing - Each parameter is a data element

Structured design - 11 © Minder Chen, Stamp Coupling Calculate Monthly Payment of a House Calculate Mortgage Payment Mortgage Payment Customer Loan Record Two module A and B are data coupled if - A calls B - B returns to A - All information passed between them are through parameter passing - A composite piece of data is passed from one module to another

Structured design - 12 © Minder Chen, Control Coupling Produce paycheck Retrieve Employee Record Produce paycheck Retrieve Employee Record Employee ID Employee Record Employee ID Tell the operator that “The Employee Record Is Not Found” Employee Record Not Found Control FlagDescriptive Flag

Structured design - 13 © Minder Chen, Scale of Cohesion Types of CohesionVisibility Strength of Cohesion Maintainability Functional Black box Sequential Not-quite so Communicational black box Procedural Gray Temporal box Logical Transparent Coincidental or white box Strong Weak Good Bad

Structured design - 14 © Minder Chen, Structure Chart and DFD This module is sequentially cohesive. This module is communicationally cohesive.

Structured design - 15 © Minder Chen, Simplify Communicational Cohesion Get Employee Name Calculate YTD Total Deduction Get Employee Name Calculate YTD Total Deduction Get Employee Name Calculate YTD Total Deduction Employee Name Employee YTD Total Deduction Employee ID Employee YTD Total Deduction Employee Name

Structured design - 16 © Minder Chen, Determine Module Cohesion Type of Cohesion Does activities performed by the module related to a single problem-related task What relates the elements within the module ? Neither data nor control Is sequence important ? Data Flow of control Is sequence important ? Are the activities performed by the elements in the same category? YES NO Functional Sequential Communicational Procedural Temporal Logical Coincidental

Structured design - 17 © Minder Chen, DETERMINE CUSTOMER DETAILS FIND CUSTOMER NAME EVALUATE LOAN STATUS DETERMINE CUSTOMER DETAILS Customer Account Number Customer Name Customer Loan Status Customer Account Number Customer Name A Communicationally Cohesive Module at the Bottom of a Structure Chart A Communicationally Cohesive Module Halfway Up a Structure Chart Each of These Functionally Cohesive Module is at the Bottom of a Structure

Structured design - 18 © Minder Chen, GET RANGES GET TIMES GET AZIMUTHS GET SATELLITE TRAJECTORY GET ELEVATION A Functionally Cohesive Module Very High in a Structure Chart Satellite Trajectory Elevation Ranges Azimuths Times

Structured design - 19 © Minder Chen, The Impact of Module Numbers on Cost Intermodule Effects (Coupling) Cost Due to Intramodule Effects (Cohesion) High Low Cost Number of Modules SmallLarge

Structured design - 20 © Minder Chen, Four Basic Types of Modules Coordinate control Transform (Process) Efferent (Output) Afferent (Input)

Structured design - 21 © Minder Chen, Idea System Shape of a Structure Chart Afferent branch Transform branch Efferent branch

Structured design - 22 © Minder Chen, Idea System Shape of a Structure Chart High fan-out High fan-in

Structured design - 23 © Minder Chen, The Procedure of Deriving Structure Charts from Data Flow Diagrams Evaluate a detailed DFD Type of DFD Identify central transform of the DFD Map to transaction structure Map to transform structure Refined the Structure Chart Identify transaction types and transaction center of the DFD Transaction Analysis Transform Analysis

Structured design - 24 © Minder Chen, P OUTPUT FUNCTION C P INPUT FUNCTION B P INPUT FUNCTION D P OUTPUT FUNCTION A P INPUT FUNCTION C P OUTPUT FUNCTION B P TRANSFORM FUNCTION A P TRANSFORM FUNCTION B P INPUT FUNCTION A BOUNDARY B A DDATA STORE D DDATA STORE B DDATA STORE E M L K J I H G F E D C B A Afferent Central Transform Efferent Transform Analysis

Structured design - 25 © Minder Chen, TRANSFORM FUNCTION A TRANSFORM FUNCTION B INPUT FUNCTION A INPUT FUNCTION D INPUT FUNCTION B OUTPUT FUNCTION A INPUT FUNCTION C OUTPUT FUNCTION C BOSS CENTRAL TRANSFORM CONTROLLER OUTPUT FUNCTION B E & F J & I J G & H E, F, & G I J G I F K E C

Structured design - 26 © Minder Chen, Transaction Analysis DFD Get Customer Transactio n Process Customer Transaction Change Customer Record Add New Customer Get Customer Transaction Delete Customer Record Tx-Code Structure Chart Customer Information System Main Menu 1. Add New Customer 2. Change Customer Record 3. Delete Customer Record A Transaction Selection Screen

Structured design - 27 © Minder Chen, Determine Implementation Boundaries Manual Real-time Batch On-line

Structured design - 28 © Minder Chen, Processor Model: Allocation of essential Model Components to Processors Essential Model Processor 1 Processor 2 Processor 3 Processor Level Implementation Model    Netware LAN  UNIX Server T1 TCP/IP Mainframe Allocating processes and data stores to processors