© Farhan Mir 2008 IMS MIS Development BBA (IT) 6 th (Lectures ) (Information System Development Methodologies) Course Lecturer: Farhan Mir

© Farhan Mir 2008 IMS A methodology is a pompous word for “method” investigation, research and discourse about methods a set of techniques, tools, methods with some underlying philosophy

© Farhan Mir 2008 IMS Information Systems Development Methodologies Structured Analysis, Design and Implementation of Information Systems (STRADIS) Yourdon Systems Method (YSM) Information Engineering (IE) Structured Systems Analysis and Design Methodology (SSADM) Merise Jackson Systems Development (JSD) Object-oriented Analysis Information Systems Work and Analysis of Changes (ISAC) Effective Technical and Human Implementation of Computer-based Systems (ETHICS) Soft System Methodology (SSM) Multiview Process Innovation Rapid Application Development (RAD) KADS Euromethod

© Farhan Mir 2008 IMS Some methodologies with examples of specific methods Structured methodologies Yourdon, SSDAM, Ward-Mellor Object-oriented methodologiesShlaer-Mellor Soft systems methodologies Ethics, Multiview

© Farhan Mir 2008 IMS Some Tools ERDs DFDs Rich pictures STDs Structure charts Formal logics Object models Prototypes ELHs JSP Normalisation Data dictionaries PDL Decision tables / trees

© Farhan Mir 2008 IMS Each methodology will use several of these tools with different emphasis, for different reasons, in a different order…...

© Farhan Mir 2008 IMS New methodologies evolves because perceived weaknesses in all other methodologies changed and improved technologies case, programming languages, hardware changed environments, markets and needs trends, fashion, band-wagon, legislation etc

© Farhan Mir 2008 IMS A quick run through some methodologies (and methods) What led to their rise, then to their fall; what were their tools and philosophies ?

© Farhan Mir 2008 IMS Structured Methods Probably the first methodology, after the so-called Test-and-Build i.e. “hacking”

© Farhan Mir 2008 IMS Structured Methods Structured analysis / design / programming started in large-scale, stable, centralised corporate DP on mainframes using COBOL “waterfall” life cycle top-down / functional decomposition

© Farhan Mir 2008 IMS Structured Methods Tools DFDs Structure Charts ERDs Data dictionaries

© Farhan Mir 2008 IMS Structured Design Technique developed to provide design guidelines What set of programs should be What program should accomplish How programs should be organized into a hierarchy Modules are shown with structure chart Main principle of program modules Loosely coupled – module is independent of other modules Highly cohesive – module has one clear task

© Farhan Mir 2008 IMS Structure Chart Created Using Structured Design Technique

© Farhan Mir 2008 IMS Structured Analysis Define what system needs to do (processing requirements) Define data system needs to store and use (data requirements) Define inputs and outputs Define how functions work together to accomplish tasks Data flow diagrams and entity relationship diagrams show results of structured analysis

© Farhan Mir 2008 IMS Data Flow Diagram (DFD) created using Structured Analysis Technique

© Farhan Mir 2008 IMS Entity-Relationship Diagram (ERD) created using the Structured Analysis technique

© Farhan Mir 2008 IMS Structured Analysis Leads to Structured Design and Structured Programming

© Farhan Mir 2008 IMS Problems with Structured Methods “Paralysis-by-analysis” / “Victorian novel” Increasingly unstable requirements : they change quicker and quicker validation : customers / users don’t understand DFDs, ERDs etc verification : lurch from one notation to the next

© Farhan Mir 2008 IMS Problems with Structured Methods lack of precision, completeness, consistency etc : much natural language is used in Structured Methods lack of user involvement feasibility sometimes poorly identified

© Farhan Mir 2008 IMS More Problems with Structured Methods Structured methods merely turn a big bit of vague text into small bits of vague text embedded in an ambiguous DFD Even if the structured analysis is provably correct, doesn’t mean the design and source code will be ! Or the machine code !

© Farhan Mir 2008 IMS Soft Systems One response to the failings of Structured Methods

© Farhan Mir 2008 IMS Origins Structured methods deal with problems; organisations have difficulties Most information processing systems have substantial human / social components are embedded in social organisations are embedded in social organisations Customers and users have partial and conflicted views on their problems

© Farhan Mir 2008 IMS Soft Systems Tools Based on systems theory holistic not reductionist subjective not objective fuzzy not well-defined purpose, boundaries, components iterative

© Farhan Mir 2008 IMS Soft Systems Tools Root definition precise verbal description of the essence of the processes CATWOE Rich pictures to build and check a “conceptual model” that form basis of information systems

© Farhan Mir 2008 IMS Soft Systems Can be grafted onto “front-end” of hard systems methods have hard systems methods embedded within them are used increasingly

© Farhan Mir 2008 IMS Object-Oriented Methods Another response to the failings of Structured Methods

© Farhan Mir 2008 IMS Object-Oriented Methods Grew out of programming eg Smalltalk, Simula Originally technical and academic Intuitive : world consists of “things”, not functions Offers framework for re-use hence quicker quality Now have industrial-strength methods

© Farhan Mir 2008 IMS Object-Oriented Methods Assume solution-domain will be entirely computer-based Use one notation throughout life-cycle

© Farhan Mir 2008 IMS Object-Oriented Tools Object models an enhanced ERD Dynamic model Harel charts Process modelDFDs