Introduction to Informatics. Software Design: Flowcharts, Modular Design and Beyond

Transcription

1 MTAT Introduction to Informatics Software Design: Flowcharts, Modular Design and Beyond Marlon Dumas marlon.dumas ät ut. ee

2 Course Objectives To introduce the flowchart notation and one of its modern variants (BPMN) To introduce the concepts of modular design and information hiding To give a flavor of current research issues in the field of software systems design 2

3 Prelude: Flowcharts 3

4 Boom Gate Flowchart 4

5 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 Major milestone in the emergence of OOP 5

6 Principles 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 programmed It is meant to hide design decision(s) from other modules in the system Many ways to decompose a system into modules: which one works better? Drexel University Software Engineering Research Group 6

7 What do we mean by better? Productivity: individual modules can be developed concurrently they are specified by their external behavior and interfaces Changeability: individual modules should be able to be changed without radical impact to the rest of the system Comprehensibility: possible to study the systems more abstractly by understanding the modules prior to understanding the code Drexel University Software Engineering Research Group 7

8 Parnas Example Input Circular Shift Alphabetize Output 8

9 Parnas Example: Flowchart Modularization Input Controller Circular Shift Alphabetizing Storage (File/Memory) Output Criteria for Decomposition: Processing Steps Drexel University Software Engineering Research Group 9

10 Parnas Example: Information Hiding Modularization Input Line Storage Storage (File/Memory) Controller Circular Shifter Alphabetizer Output Criteria for Decomposition: Information Hiding Drexel University Software Engineering Research Group 10

11 Benefits of Information Hiding Productivity Information Hiding interfaces are more abstract and have less surface better for concurrent development Changeability Information Hiding supports change much easier. The classical technique would require modifications to many modules to support most changes Comprehensibility When using IH, less detailed understanding of the overall system is required in order to understand a particular module Drexel University Software Engineering Research Group 11

12 Exercise 12

13 Beyond Information Hiding The Model-View Controller (MVC) Pattern Java Web bapplication Development Generation 1: Servlets http http Servlet Simple approach towards web-based system development Servlet does not hide very much hinformation Manages the entire UI, all of the control logic, all of the business logic, and any database interaction Drexel University Software Engineering Research Group 13

14 The MVC Pattern (cont.) Java Web bapplication Development Generation 2: Servlets & JSP s http http Servlet JSP Better separation of input and output processing Support for different output formats Servlet still knows too much about overall system Its hard to reuse certain aspects of a system using a servlet/jsp solution Drexel University Software Engineering Research Group 14

15 The MVC Pattern (cont.) Java Web Application Development Generation 3: MVC Approach 15

16 Where s the Model, View, Controller? Input Line Storage Storage (File/Memory) Controller Circular Shifter Alphabetizer Output Drexel University Software Engineering Research Group 16

17 The Death of Flowcharts? Does Parnas s paper implies that flowcharts are useless? 17

18 Modern Manifestation of Flowcharts Business Process Modeling Notation Reject order Check stock availability Send invoice Confirm order Ship goods 18

19 Business Process Management (BPM) Body of methods to design, analyze, execute and monitor business operations involving humans, software, information and physical artifacts using process models. 19

20 Examples of Business Process? Order-to-Cash Procure-to-Pay Fault-to-Resolution 20

21 My washing machine won t work! Call Centre Technician Warranty? Customer Service Dispatch Parts Store Customer fault-report-to-resolution process VAL LUE Michael Rosemann 21

22 BPM Research Questions How to use process models to integrate systems consisting of dozens or hundreds of modules? 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 million into modernizing a system? How to use process models to prioritize changes to a system? How to manage repositories consisting of hundreds or thousands of process models? 22

23 Problem: Enterprise System Integration Purchaser Supplier Inventory Planning Procurement Order Order Response Order tracking Inventory Management Financial Approval Supplier Relationshi p Managemen t Accounts Payable Change Order Change Confirmation Shipment Notice Invoice Customer Relationshi ps Managemen t Invoicing Logistics 23

24 Services and Processes in Action Purchaser s System Process Instance Process Process Instance Instance Create Order Process Response Process Instance Service Endpoint Send Order Receive Response Order Order Response Change Order Change Response Shipment Notice Invoice Supplier s System Service Endpoint Receive Order Process Instance Record Order Check Stock Send Response Process Instance Process Process Instance Instance Process Service Service Process Model(s) Interface(s) Interface(s) Model(s) 24

25 Service-Oriented Architecture (SOA) Supplier Inventory Control Service Procurement Service Invoicing Service 25

26 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 Configuration Functions, Procedures Modules Objects Components Services 26

27 Want to join the fun?