LECTURE 15 – USER INTERFACE
AND DATA STORAGE DESIGN
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Design Selection
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Physical Process
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User Interface Design
•
Data Storage Design
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DESIGN SELECTION
Design Phase
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DESIGN SELECTION
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Three main design strategies:
1. Develop a custom application in-house: Builds technical skills and
functional knowledge within the organisation.
2.
Develop the application by customizing COTS products: Customisation
by workaround or systems integration.
3.
Outsource the development of the application: Risk to compromise
confidential information, no skills learn from development.
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Aspects to consider when selecting a design strategy:
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Business need – unique, common, critical for business?
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In-house experience – does functional/technical experience exist?
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Project skills – strategic/non-strategic/desirable?
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Project management – skilled/non-skilled?
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Time frame – flexible/short/tight?
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PHYSICAL PROCESS AND DATA MODELS
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The physical models show the implementation details and
explain how the system will work, including:
 Actual, specific technology – available for the system?
 Format of information – files/databases/emails/reports?
 Human interaction with system – details on how users will
interact with the new system?
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PHYSICAL PROCESS AND DATA MODELS
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Transition to Physical DFD
1. Add implementation references – references in which data stores, data
flows and processes will be implemented.
2.
Draw a human-machine boundary – differentiate human and computer
interaction
3.
Add system-related data stores, data flows and processes – specific to
the implementation and little to do with the business process itself
4.
Update data elements in the data flows – specific details related to
implementation
5.
Update the metadata in the CASE repository – updated with
implementation specific information
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PHYSICAL PROCESS AND DATA MODELS
Example: A level 0 logical DFD and the corresponding level 0 physical DFD for the dentist
office appointment system.
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Level 0 Logical DFD
PHYSICAL PROCESS AND DATA MODELS
Level 0 Physical DFD
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USER INTERFACE DESIGN
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The user interface is the system which helps users communicate with the
computer system and/or the application system.
Aims of good user interface design:
pleasing to the eye
 simple to use
 minimise user’s effort to accomplish tasks
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Principles of user interface design:.
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Layout – consistency throughout the system
Content awareness – for status of system
Aesthetics – functional vs. pleasing the user
User experience – easy to use vs. easy to learn
Consistency – in functionality throughout the system
Minimal user effort – simple to use
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USER INTERFACE DESIGN
Example. An interface structure design (for a Web site selling books, music, clothes, etc.)
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USER INTERFACE DESIGN
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Common elements of the user interface:
Navigation – language, menus, direct manipulation
 Inputs – text, numbers, selection boxes, etc.
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Outputs – graphs, reports, summaries, etc.
Navigation – the goal is to make the system as simple as possible to use
Prevent mistakes – e.g. don’t display commands that cannot be used
 Simplify recovery from mistakes – e.g. the typical ‘undo’ option
 Use consistent grammar order – e.g. object then action or vice versa
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USER INTERFACE DESIGN
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The system should provide navigation messages (clear, concise and
complete) to the user in order to respond to users’ action and
inform of the status of the interaction:
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Error message
Confirmation message
Acknowledge message
Delay message
Help message
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USER INTERFACE DESIGN
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Input – the goal is to simply and easily capture accurate information
Adequate online and batch processing – is real time information needed?
 Capture data at the source – avoid intermediary collection
 Minimise keystrokes – minimise cost in time and money
 Validate input – very important to ensure accuracy
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Output – the goal is to present information to users so they can accurately
understand it with the least effort
Understand report usage – design accordingly to users needs
 Manage information load – not all information, not a data dump
 Minimise bias – ways of sorting records, highlighting fields, etc.
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DATA STORAGE DESIGN
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The objectives in the design of data storage organization are:
 The data must be available when the user wants to use it
 The data must have integrity - It must be accurate and consistent
 Efficient storage of data as well as efficient updating and retrieval
 The information obtained from the stored data must be in an integrated
form to be useful for
Managing
 Planning
 Controlling
 Decision making
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DATA STORAGE DESIGN
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Step 1. Select format of data storage
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Files
The format can also be a combination of these two
Databases
Criteria for selection: data types, type of application system, existing software
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formats, future needs.
Types of files:
master files – store core information to the business
 look-up files – store static values used commonly for validation
 transaction files – information to update the master file
 audit files – records the ‘before’ and ‘after’ images of data.
 history files – stores past transactions
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DATA STORAGE DESIGN
Types of databases:
legacy – based on older technology, e.g. hierarchical and network databases
 relational – based on collection of tables each with a primary key
 object-oriented – based on the object oriented paradigm
 multi-dimensional – used for data warehousing, that is, taking data from the
company’s transaction system, transforming it, and storing in a data
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DATA STORAGE DESIGN
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Step 2. Optimise performance of data storage
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Optimise storage efficiency
Optimise access speed
Estimate adequate storage size
Reading: (Dennis&Wixom, chapters 8,10,11).
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