Chapter 14 Construct, Deliver, and Maintain Systems Projects.
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Transcript of Chapter 14 Construct, Deliver, and Maintain Systems Projects.
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Chapter 14Construct, Deliver, and Maintain
Systems Projects
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Objectives for Chapter 14• The sequence of events that constitutes the in-house
development phase of SDLC
• Tools used to improve the success of systems construction and delivery activities: CASE tools; PERT and Gantt charts
• Distinction between structured and object-oriented design approaches
• Multi-level DFDs in the design of business processes
• Types of systems documentation and the purposes they serve
• The role of accountants in the construction and delivery of systems
• The advantages and disadvantages of the commercial software option
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Systems Development Life Cycle
1. Systems Strategy - Assessment - Develop Strategic Plan
1. Systems Strategy - Assessment - Develop Strategic Plan
2. Project Initiation - Feasibility Study - Analysis - Conceptual Design - Cost/Benefit Analysis
2. Project Initiation - Feasibility Study - Analysis - Conceptual Design - Cost/Benefit Analysis
3. In-house Development - Construct - Deliver
3. In-house Development - Construct - Deliver
4. Commercial Packages - Configure - Test - Roll-out
4. Commercial Packages - Configure - Test - Roll-out
5. Maintenance & Support - User help desk - Configuration Management - Risk Management & Security
5. Maintenance & Support - User help desk - Configuration Management - Risk Management & Security
SSystemystem Interfaces, Architecture Interfaces, Architecture and Uand User ser RRequirementsequirements
BBusiness usiness RRequirementsequirements
High Priority Proposals undergo High Priority Proposals undergo Additional Study and DevelopmentAdditional Study and Development
FeedbackFeedback::User requests for New SystemsUser requests for New Systems
Selected System Proposals Selected System Proposals go forward for Detailed go forward for Detailed
DesignDesign
New and Revised New and Revised Systems Enter into Systems Enter into
ProductionProduction
Business Needs and Strategy
Legacy Situation
FeedbackFeedback::User requests for System User requests for System Improvements and SupportImprovements and Support
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Overview of Phases 3, 4 and 5• Phase 3 - In-House Development
– appropriate when organizations have unique information needs
– steps include: • analyzing user needs• designing processes and databases• creating user views• programming the applications• testing and implementing the completed system
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Overview of Phases 3, 4 and 5• Phase 4 - Commercial Packages
– when acceptable, most organizations will seek a pre-coded commercial software package
– advantages: • lower initial cost• shorter implementation time• better controls• rigorous testing by the vendor
– risks:• must adequately meet end users’ needs• compatible with existing systems
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Overview of Phases 3, 4 and 5• Phase 5 - Maintenance and Support
– acquiring and implementing the latest software versions of commercial packages
– making in-house modifications to existing systems to accommodate changing user needs
– may be relatively trivial, such as modifying an application to produce a new report, or more extensive, such as programming new functionality into a system
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Phase 3Systems Strategy
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Why Up to 25% of All Systems Projects Fail
• Poorly specified systems requirements– communication problems– time pressures
• Ineffective development techniques– paper, pencils, templates, erasers instead of
software tools, such as CASE• Lack of user involvement in systems
development
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Prototyping• A technique for providing a preliminary
working version of the system• Built quickly and relatively inexpensively
with the intention it will be modified• End users work with the prototype and
make suggestions for changes.– A better understanding of the true
requirements of the system is achieved.
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Prototyping Techniques
IdentifyConceptualUserSpecifications
DevelopPrototype
PresentPrototypeto Users
ObtainUserFeedback
ChangePrototypePer UserFeedback
DevelopPrototypeinto FinishedSystem
Discard Prototypeand DevelopSystem UnderTraditionalSDLC Procedures
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Computer-Aided Software Engineering (CASE)
• CASE technology involves the use of computer systems to build computer systems.
• CASE tools are commercial software products consisting of highly integrated applications that support a wide range of SDLC activities.
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Uses of CASE Tools
• Define user requirements
• Create physical databases from conceptual user views
• Produce system design specifications
• Automatically generate program code
• Facilitate the maintenance of programs created by both CASE and non-CASE techniques
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CASE Spectrum of Support Tools for the SDLC
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1
27
3
4
6
8
9
Purch
ase E
quipm
ent
Install and Test Equipment
Design Data Model Create Data Structures
5
Design Process
Code Programs Test
Prog
ram
s
Prepare
Doc
umen
tation
Convert Data Files
Test System
Train Personnel
Cut Over
to N
ew Syste
m
A = 3 Wee
ks
B = 4 Weeks
C = 4 Weeks
D = 2 Weeks
E = 5 Weeks
F = 5 Weeks G =
3 W
eeks
H = 3 W
eeks
I = 3 Weeks
J = 4 Weeks
L = 4 Week
s
K = 3 Weeks
Construct Phase Deliver Phase
Project Evaluation and Review Technique (PERT)
PERT charts show the relationship among key activities that constitute the construct and delivery process.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
Project Week
Purchase Equipment
Design Data Model
Install and Test Equipment
Design Process
Code Programs
Test Programs
Create Data Structures
Prepare Documentation
Convert Data Files
Test System
Cut Over to New System
Train Personnel
Cur
rent
Poi
nt in
Tim
e
Budgeted
Actual
Gantt Chartrepresents time horizontally and activities vertically
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Structured Design Approach
• A disciplined way of designing systems from the top down
• Starts with the “big picture” of the proposed system and gradually decomposes it into greater detail so that it may be fully understood
• Utilizes data flow diagrams (DFDs) and structure diagrams
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Object-Oriented Design Approach
• It builds information systems from reusable standard components or objects.
• Once created, standard modules can be used in other systems with similar needs.
• A library of modules can be created for future use.
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Elements of the Object-Oriented Approach
• Objects: equivalent to nouns– vendors, customers, inventory, etc.
• Attributes: equivalent to adjectives– part number, quantity on hand, etc.
• Operations: equivalent to verbs – review quantity on hand, reorder item
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Characteristics of an Inventory Object
Part Number DescriptionQuantity on Hand Reorder Point Order Quantity
Inventory
Reduce ReviewQuantity
Reorder Replace
Attributes
Object
Operations
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Classes and Instances• An object class is a logical grouping of
individual objects that share the same attributes and operations.
• An object instance is a single occurrence of an object within a class.
Inventory
Wheel Bearing Alternator Water Pump
ObjectClass
Instance
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Inheritance
• Inheritance means that each object instance inherits the attributes and operations of the class to which it belongs.
• Object classes may also inherit from other object classes.
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Systems Design
• Follows a logical sequence of events:– model the business process and design
conceptual views– design normalized database tables – design physical user views (output and input
views)– develop process modules – specify system controls– perform system walkthroughs
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Data Modeling
• Formalizes the data requirements of the business process as a conceptual model
• Entity-relationship diagram (ERD) – the primary tool for data modeling– used to depict the entities or data objects in the
system
• Each entity in an ER diagram is a candidate for a conceptual user view that must be supported by the database.
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Normalization• User views in the data model must be
supported by normalized database tables.• Normalization of database tables:
– A process of organizing tables so that entities are represented unambiguously
– Eliminates data redundancies and associated anomalies– Depends on the extent that the data requirements of all
users have been properly specified in the data model– REA modeling facilitates normalization by identifying
entities at their most fundamental levels– The resulting databases will support multiple user views
• Described in more detail in chapter 9
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Physical User Views: Output Views
• Output is the information produced by the system to support user tasks and decisions.
• Output attributes:-relevant
-summarization
-except orientation
-timely-accurate-complete-concise
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Output Reporting Techniques
• Different users prefer different styles of output… – tables, matrices, charts, and graphs
• …and modes of output – hard copy vs. display screen.
• Systems designers must identify these styles and provide output in the desired style.
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• Input views are used to capture the relevant facts in business processes and transactions (e.g., via REA model):– Resources– Events– Agents
• Input may be either hard copy input documents or electronic input.
Physical User Views: Input Views
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Designing Hard Copy Input
• Items to Consider:– How will the document be handled? – How long will the form be stored and in what
type of environment?– How many copies are required?– What size form is necessary?
• Non-standard form can cause printing and storage problems.
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Designing Electronic Input Input may be from either hardcopy or electronic
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Data Entry Devices
• Point-of-sale terminals
• Touch screens
• Mouse
• Magnetic ink character recognition devices
• Optical character recognition devices
• Voice and touch-tone recognition devices
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Designing Process Modules
• Begins with the DFDs produced in the general design phase
• First, decompose the existing DFDs to a degree of detail that will serve as the basis for creating structure diagrams
• Structure diagrams provide the blueprints for writing the actual program modules
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Data Flow Diagrams (DFDs)
• Used to represent multiple levels of detail– Can represent system physically or logically
• Decompose high-level DFDs into more detailed lower-level DFDs
• Context-level DFDs represent an overview of the business activities and the primary transactions processed by the system. – Do not include detailed definitions of data files
and specific procedures
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Lower-Level DFD for an AP Process
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The Modular Approach
• Each module performs a single task.
• Correctly designed modules possess two attributes:– loosely coupled - low amounts of exchange
of data between modules– strongly cohesive - small number of tasks
performed in each module
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Designing System Controls• The last step in the detailed design phase• Need to consider:
– computer processing controls– data base controls– manual controls over input to and output from the
system– operational environment controls
• Allows the design team to review, modify, and evaluate controls with a system-wide perspective that did not exist when each module was being designed independently
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Systems Walkthrough
• Usually performed by the development team– Ensure that design is free from conceptual
errors that could become programmed into the final system
• Some firms use a quality assurance (QA) group to perform this task. – An independent group of programmers,
analysts, users, and internal auditors
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Program Application Software• If the organization intends to develop
software in-house, then a programming language must be selected:– procedural languages or 3GLs COBOL– event-driven languages Visual Basic– object-oriented languages Java
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The Modular Approach to Programming
• Promotes programming efficiency – modules can be both programmed and tested
independently
• Promotes maintenance efficiency – small modules are easier to analyze and
change
• Promotes greater control – modules are less likely to contain material
errors of fraudulent logic
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Deliver the System:Testing
• Programs must be thoroughly tested before being implemented. – All logic procedures should be tested.
• Test individual modules with test data containing both “good” and “bad” data.
• After testing individual modules, the entire system should tested as a whole.
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• Describes how the system works • Documentation should be provided for:
– designers and programmers - comment lines in programs, system flowcharts, and program flowcharts
– operator documentation - run manuals– user documentation - instructions on how to use
the system, tutorials, and help features– accountants and auditors - all of the above as
well as document flowcharts
Deliver the System:Documenting
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• The transfer of data from its current form to the format or medium required by the new system
• Control risks with the following procedures:– validation – inspect old database before
conversion– reconciliation – reconcile the new
converted database against the original– backup - keep copies of the original files
against discrepancies in the converted data
Deliver the System:Converting the Databases
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Three data conversion cutover approaches:• Cold turkey - switch to the new system all at once
and simultaneously terminate the old system– riskiest approach
• Phased - modules are implemented in a piecemeal fashion– reduces risk of a devastating failure
• Parallel operation - the old system and new system are run simultaneously for awhile– safest, yet costliest, approach
Deliver the System:Converting the Databases
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• Objective: measure the success of the new system.– do after initial problems have been addressed
• Assess:– system design adequacy– accuracy of time, cost, and benefit estimates
• Provides feedback to improve future systems development projects, including changes to the current system
Deliver the System:Post-Implementation Review
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Deliver the System:The Role of Accountants
• Most system failures are due to poor design and improper implementation.
• Accountants should provide their expertise to help avoid inadequate systems by:– providing technical expertise for financial reporting
requirements– specifying documentation standards for auditing
purposes– verifying control adequacy in accordance with SAS
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Phase 4Commercial Packages
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The Purchase of Commercial Systems Packages
• Four factors have stimulated the growth of commercial software:– relatively low cost– prevalence of industry-specific vendors– growing demand by small businesses– trend toward downsizing and distributed data
processing
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Trends in Commercial Packages
• Turnkey systems - completely finished and tested systems ready for implementation
• Backbone systems - provide a basic system structure on which to build.
• Vendor-supported systems - customized and maintained by a vendor for a customer
• ERP systems - difficult to classify since they have characteristic of all of the above.– See chapter 11 for more details on ERP systems
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Pros and Cons of Commercial Packages
• Advantages:– decreased implementation time– decreased cost– reduced probability of program errors
• Disadvantages:– dependent on the vendor for maintenance– less flexibility in system– greater difficulty in modifying the system as
needs change over time
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Four Steps in Choosing a Commercial Package
1. Analyze needs and develop detailed specifications of the system requirements.
2. Send out the request for proposals to all prospective vendors to serve as a comparative basis for initial screening.
3. Gather the facts about each vendor’s system using multiple sources and techniques.
4. Analyze the findings and make a final selection.
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Phase 5Maintenance and
Support
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Maintenance and Support
• Approximately 80% of the life and costs of SDLC• Can be outsourced or done in-house resources• End user support is a critical aspect of
maintenance that can be facilitated by:– knowledge management - method for gathering,
organizing, refining, and disseminating user input– group memory - method for collecting user input for
maintenance and support
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The Iceberg Effect