MTAT 05 074MTAT.05.074Introduction to Informatics

Software Design: Flowcharts, Modular Design and Beyond

Marlon Dumas

marlon.dumas ät ut . ee

Course ObjectivesCourse Objectives

f f• To introduce the flowchart notation and one of its modern variants (BPMN)

• To introduce the concepts of modular design and• To introduce the concepts of modular design and information hiding

• To give a “flavor” of current research issues in the field of gsoftware systems design

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Prelude: FlowchartsPrelude: Flowcharts

3http://fishbowl.pastiche.org/archives/pictures/life-lessons-flowchart.png

Boom Gate FlowchartFlowchart

4http://visl.technion.ac.il/projects/2004sum04/flowchart1.jpg

D.L. Parnas: On the Criteria to Be Used in Decomposing Systems into Modules

• One of the foundational papers in the field of software design

• At the time, implementation was the main concern, design was rather primitive, g p

• Major milestone in the emergence of OOP

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Principles of Modular DesignPrinciples of Modular Design

• A module is a “piece of software” with a well defined interface

• It should be small and simple enough to be thoroughly understood and well programmedg y p g

• It is meant to hide design decision(s) from other modules in the systemmodules in the system

• Many ways to decompose a system into modules: which one works better?modules: which one works better?

6© Drexel University Software Engineering Research Group

What do we mean by “better”?What do we mean by better ?

• Productivity: individual modules can be developed concurrently – they are specified by their external behavior and interfacestheir external behavior and interfaces

• Changeability: individual modules should be able to be changed without radical impact to theable to be changed without radical impact to the rest of the system

• Comprehensibility: possible to study the p y p ysystems more abstractly – by understanding the modules prior to understanding the code

7© Drexel University Software Engineering Research Group

Parnas ExampleParnas Example

Input

CircularShift

Alphabetize

Output

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Parnas Example: Flowchart ModularizationParnas Example: Flowchart Modularization

Input

CircularShift

Controller StAlphabetizing

Controller Storage(File/Memory)

Output

Criteria for Decomposition: Processing Steps

9© Drexel University Software Engineering Research Group

Parnas Example: Information Hiding Modularization

Input

Storage(Fil /M )Line Storage

Ci lController

(File/Memory)

CircularShifter

Alphabetizer

Output

Criteria for Decomposition: Information Hiding

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p g

© Drexel University Software Engineering Research Group

Benefits of Information HidingBenefits of Information Hiding

• Productivity – Information Hiding interfaces are more abstract and have “less surface” better for concurrent developmentp

• Changeability – Information Hiding supports change much easier. The classical technique would require modifications to many modules to support mostmodifications to many modules to support most changes

• Comprehensibility – When using IH, less detailed understanding of the overall system is required inunderstanding of the overall system is required in order to understand a particular module

11© Drexel University Software Engineering Research Group

Exercise…

12http://visl.technion.ac.il/projects/2004sum04/flowchart1.jpg

Beyond Information Hiding –The Model-View Controller (MVC) Pattern

J W b A li ti D l t G ti 1 S l tJava Web Application Development – Generation 1: Servlets

http• Simple approach

towards web-based Servlet

httpsystem development– Servlet does not hide very

h i f timuch information• Manages the entire UI, all

of the control logic, all of the business logic, and any database interaction

13© Drexel University Software Engineering Research Group

The MVC Pattern (cont )The MVC Pattern (cont.)

J W b A li ti D l t G ti 2 S l t & JSP’

• Better separation of input

Java Web Application Development – Generation 2: Servlets & JSP’s

http

• Better separation of input and output processing

• Support for different outputServlet • Support for different output formats

• Servlet still “knows” too much

http

Servlet still knows too much about overall system– Its hard to reuse certain JSP

httpaspects of a system using a servlet/jsp solution

14© Drexel University Software Engineering Research Group

The MVC Pattern (cont )The MVC Pattern (cont.)

15Java Web Application Development – Generation 3: MVC Approach

Where’s the Model View Controller?Where s the Model, View, Controller?

Input

Storage(Fil /M )Line Storage

Ci lController

(File/Memory)

CircularShifter

Alphabetizer

Output

16© Drexel University Software Engineering Research Group

The Death of Flowcharts?The Death of Flowcharts?

• Does Parnas’s paper implies that flowcharts are useless?

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Modern Manifestation of Flowcharts –Business Process Modeling Notation

Reject order

Check stock availability Send invoice

Confirm order

Ship goodsShip goods

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Business Process Management (BPM)g ( )

Body of methods to design, analyze, execute and monitor business operations involving humans, software, information and physical artifacts using process models.

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Examples of Business Process?p

• Order-to-Cash• Procure-to-Pay • Fault-to-Resolution

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“My washing machine won’t work!”

Warranty?

TechnicianCall Centre

CustomerP t

Technician

CustomerCustomerPartsStoreService

Dispatch

LUE

fault-report-to-resolution process VAL

21© Michael Rosemann

BPM Research QuestionsBPM – Research Questions

• How to use process models to integrate systems consisting of dozens or hundreds of “modules”?H t d l t th i• How to use process models to assess the economic value of a systems or its modules?How to use process models to justify investing EUR 2• How to use process models to justify investing EUR 2 million into modernizing a system?How to use process models to prioritize changes to aHow to use process models to prioritize changes to a system?

• How to manage repositories consisting of hundreds or g p gthousands of process models?

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Problem: Enterprise System Integration

SupplierPurchaser

OrderProcurement

InventoryInventoryManagement

Ordertracking

Order Response

Change Order

ProcurementPlanningManagementg

Change ConfirmationSupplierRelationshiFinancial

Approval Logistics

CustomerRelationshipsMShipment Notice

Invoice

pManagement

pp gManagement

In oicingAccounts Payable Invoicing

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Services and Processes in Action

Purchaser’sSystem

Supplier’sSystem

Process

Order

Order Response

ServiceEndpointProcess

Instance

ServiceEndpoint

ProcessInstance

Process RecordOrder Response

Change Order

InstanceProcessInstance

Create

SendOrder

ReceiveOrder

Order

CheckStock

Change Response

Shipment Notice

Order

ProcessInstance

Stock

SendResponse

ReceiveResponse

ProcessResponse Shipment Notice

InvoiceProcessInstance

InstanceProcessInstanceProcess

Instance

Response

sta ce

Process Service Service Process

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ProcessModel(s)

ServiceInterface(s)

ServiceInterface(s)

ProcessModel(s)

Service-Oriented Architecture (SOA)

Supplier

Inventory ControlService

Procurement Service

Invoicing Service

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Modular Design Nowadays

• Closer communication between business & IT sharing common concepts and models

• Shift from “programming in the small” to “programming in the large” with emphasis on:– Integration– Adaptation– Configurationg

Functions, Procedures ObjectsModules ServicesComponentsProcedures ObjectsModules Components

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Want to join the fun?Want to join the fun?

• http://sep.cs.ut.ee/• http://math.ut.ee/~dumas/p

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