1. Information Systems Analysis and Design Reviews of IS and Software Process Spring Semester 2012-2013

2. Principles of Reviews  Systems concept  Computer-based IS and software intensive systems  Analysis and design in the development of above systems 2

3. What is a System?  A set of interrelated components  With a clearly defined boundary  Working together  To achieve a common set of objectives  By accepting inputs and producing output  In an organized transformation process (O’Brien and Marakas, 2008) 3

4. Basic Functions of a System  Input –Capturing and assembling elements that enter the system to be processed  Processing –Transformation process that converts input into output  Output –Transferring transformed elements to their ultimate destination 4

5. Cybernetic System  All systems have input, processing, and output  A cybernetic system, a self-monitoring, self- regulating system, adds feedback and control: –Feedback is data about the performance of a system –Control involves monitoring and evaluating feedback to determine whether a system is moving toward the achievement of its goal 5

6. A Cybernetic System 6

7. A Business as a System 7

8. Other System Characteristics  If a system is one of the components of a larger system, it is a subsystem –The larger system is an environment  Several systems may share the same environment –Some may be connected via a shared boundary, or interface 8

9. Components of an IS  O’Brien and Marakas (2008) 9

10. Information System Resources  People Resources –Specialists –End users  Hardware Resources –Machines –Media  Software Resources –Programs –Procedures 10

11. Information System Resources  Data Resources –Product descriptions, customer records, employee files, inventory databases  Network Resources –Communications media, communications processors, network access and control software  Information Resources –Management reports and business documents using text and graphics displays, audio responses, and paper forms 11

12. Data Versus Information  Data are raw facts about physical phenomena or business transactions  Information is data that has been converted into meaningful and useful context for end users  Examples: –Sales data is names, quantities, and dollar amounts –Sales information is amount of sales by product type, sales territory, or salesperson 12

13. IS Activities  Input of data resources –Data entry activities  Processing of data into information –Calculations, comparisons, sorting, and so on  Output of information products –Messages, reports, forms, graphic images  Storage of data resources –Data elements and databases  Control of system performance –Monitoring and evaluating feedback 13

14. Our Focus  Computer-based information systems  Software-intensive systems  Analysis and design in the development of above systems 14

15. Software  What is it? 15

16. Software  The concept of software resources includes all sets of information processing instructions.  This generic concept of software includes not only the sets of operating instructions called programs, which direct and control computer hardware, but also the sets of information processing instructions called procedures that people need. (O’Brien and Marakas, 2008) 16

17. Software  Computer programs and associated documentation. Software products may be developed for a particular customer or may be developed for a general market. (Sommerville, 2010) 17

18. Software products  Generic products –Stand-alone systems that are marketed and sold to any customer who wishes to buy them. –Examples – PC software such as graphics programs, project management tools; CAD software; software for specific markets such as appointments systems for dentists.  Customized products –Software that is commissioned by a specific customer to meet their own needs. –Examples – embedded control systems, air traffic control software, traffic monitoring systems. 18

19. Product specification  Generic products –The specification of what the software should do is owned by the software developer and decisions on software change are made by the developer.  Customized products –The specification of what the software should do is owned by the customer for the software and they make decisions on software changes that are required. 19

20. The software process  A structured set of activities required to develop a software system.  Many different software processes but all involve: –Specification – defining what the system should do; –Design and implementation – defining the organization of the system and implementing the system; –Validation – checking that it does what the customer wants; –Evolution – changing the system in response to changing customer needs. 20

21. Software process model  A software process model is an abstract representation of a process. It presents a description of a process from some particular perspective. 21

22. Software process descriptions  When we describe and discuss processes, we usually talk about the activities in these processes such as specifying a data model, designing a user interface, etc. and the ordering of these activities.  Process descriptions may also include: –Products, which are the outcomes of a process activity; –Roles, which reflect the responsibilities of the people involved in the process; –Pre- and post-conditions, which are statements that are true before and after a process activity has been enacted or a product produced. 22

23. Plan-driven and agile processes  Plan-driven processes are processes where all of the process activities are planned in advance and progress is measured against this plan.  In agile processes, planning is incremental and it is easier to change the process to reflect changing customer requirements.  In practice, most practical processes include elements of both plan-driven and agile approaches.  There are no right or wrong software processes. 23

24. Software process models  The waterfall model –Plan-driven model. Separate and distinct phases of specification and development.  Incremental development –Specification, development and validation are interleaved. May be plan-driven or agile.  Reuse-oriented software engineering –The system is assembled from existing components. May be plan-driven or agile.  In practice, most large systems are developed using a process that incorporates elements from all of these models. 24

25. The waterfall model 25