APSI 02 ISAD ISandSE Reviews IA EarlyDiscussion
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Transcript of APSI 02 ISAD ISandSE Reviews IA EarlyDiscussion
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INFORMATION SYSTEMSANALYSIS AND DESIGN
Reviews of IS and Software Process
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Principles of Reviews
! Systems concept
! Computer-based IS and software intensivesystems
! Analysis and design in the development ofabove systems
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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)
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Basic Functions of a System
! Input
!Capturing and assembling elements that enterthe system to be processed
! Processing! Transformation process that converts input into
output
!
Output! Transferring transformed elements to their
ultimate destination
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Cybernetic System
! All systems have input, processing, andoutput
! A cybernetic system, a self-monitoring, self-
regulating system, adds feedback andcontrol:! Feedback is data about the performance of a
system
!Control involves monitoring and evaluatingfeedback to determine whether a system ismoving toward the achievement of its goal
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A Cybernetic System
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A Business as a System
!
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Other System Characteristics
! If a system is one of the components of alarger system, it is a subsystem
! The larger system is an environment
! Several systems may share the sameenvironment
! Some may be connected via a shared
boundary, or interface
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Components of an IS
! O’Brien and Marakas (2008)
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Information System Resources
! People Resources
! Specialists
! End users
! Hardware Resources
!Machines
!Media
! Software Resources!Programs
!Procedures
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Information System Resources
! Data Resources
! Product descriptions, customer records, employeefiles, inventory databases
! Network Resources! Communications media, communications
processors, network access and control software
! Information Resources
! Management reports and business documentsusing text and graphics displays, audio responses,and paper forms
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Data Versus Information
! Data are raw facts about physicalphenomena or business transactions
! Information is data that has been converted
into meaningful and useful context for endusers
! Examples:
! Sales data is names, quantities, and dollar
amounts! Sales information is amount of sales by
product type, sales territory, or salesperson
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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
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Our Focus
! Computer-based information systems
! Software-intensive systems
! Analysis and design in the development ofabove systems
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Software
! What is it?
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Software
! The concept of software resources includesall sets of information processinginstructions.
! This generic concept of software includesnot only the sets of operating instructionscalled programs, which direct and controlcomputer hardware, but also the sets of
information processing instructions calledprocedures that people need. (O’Brien andMarakas, 2008)
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Software
! Computer programs and associateddocumentation. Software products may bedeveloped for a particular customer or may
be developed for a general market.(Sommerville, 2010)
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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; CADsoftware; software for specific markets such asappointments 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.
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Product specification
! Generic products
! The specification of what the software shoulddo is owned by the software developer and
decisions on software change are made by thedeveloper.
! Customized products
! The specification of what the software should
do is owned by the customer for the softwareand they make decisions on software changesthat are required.
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Questions?20
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The software process
! A structured set of activities required todevelop a software system.
! Many different software processes but allinvolve:
! Specification – defining what the system shoulddo;
! Design and implementation – defining theorganization of the system and implementing thesystem;
! Validation – checking that it does what thecustomer wants;
! Evolution – changing the system in response tochanging customer needs.
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Software process model
! A software process model is an abstractrepresentation of a process. It presents adescription of a process from some
particular perspective.
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Software process descriptions
! When we describe and discuss processes, weusually talk about the activities in theseprocesses 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 hasbeen enacted or a product produced.
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Plan-driven and agile processes
! Plan-driven processes are processes where all
of the process activities are planned in advanceand progress is measured against this plan.
! In agile processes, planning is incremental andit is easier to change the process to reflectchanging customer requirements.
! In practice, most practical processes include
elements of both plan-driven and agileapproaches.
! There are no right or wrong software processes.
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Software process models
! The waterfall model! Plan-driven model. Separate and distinct phases of
specification and development.
! Incremental development
! Specification, development and validation areinterleaved. 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 developedusing a process that incorporates elementsfrom all of these models.
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The waterfall model