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Definitions of GIS
• Works with geographic information
• Performs data input, management, manipulation/analysis, and output functions
• Composed of hardware, software, people, and institutional context
GIS Design
• Perspective-oriented definitions (management):
“[GIS is] an institutional entity, reflecting an organizational structure that integrates technology with a database, expertise and continuing financial support over time.”
(Carter, 1989: 3)
GIS Design
• Procedures for the development, implementation, and management of a GIS in the context of an organization’s analytical needs and institutional framework
GIS Design
• Project GIS– an individual GIS-based analysis or task with a
limited scope; once the task is complete, the project is finished (e.g. your final project)
• Enterprise GIS– a GIS ‘system’ developed to meet an
organization’s needs and goals over the life of the organization; many different users and tasks (e.g. PA DOT)
GIS Design
• Many enterprise GIS fail because they are designed poorly (or not at all!)
• What is failure:– not meeting the expectations of those
supposedly benefitting from the implementation of a GIS (usually in terms of time, efficiency, money, communication, new products, new services, etc.)
GIS Design
Overall GIS Design
GIS System Design
GIS Software Design
Technical Design Issues
Institutional Design Issues
(Demers, 1997)
GIS Design
• Technical design (internal)– system functionality and the database
– Will the system offer appropriate analysis functions?
– Is the necessary data available and in the right format?
– Do employees have the technical expertise to use the system?
GIS Design
• Institutional design (external)– organizational setting
– Adequate funding from upper level management?
– Cost of data?– Software support from the GIS vendor?
GIS Design• Waterfall design model
– (adapted from software engineering)Requirements specification
Preliminary design
Detailed design
Coding
Unit testing
Integrated testing
System testing
Maintain
GIS Design• Waterfall design model
– with feedback loopsRequirements specification
Preliminary design
Detailed design
Coding
Unit testing
Integrated testing
System testing
Maintain
GIS Design
• Requirements specification– Conceptually, what is the system supposed to
do?
• Preliminary design– Develop system architecture
GIS Design
• Detailed design– Describe and develop sub-elements of the
system to address specific analytical tasks
• Coding– Write scripts and macros for those tasks and
application customization
GIS Design
• Unit testing– Test from the ‘bottom up’ - test isolated
functions
• Integrated Testing– Test from the ‘top-down’ - test major functions
GIS Design
• System testing– Test from the entire system, user-like testing
• Maintain– Maintain operations of the system throughout
its lifetime
GIS Design
• Advantages of the waterfall model
– logical– feedback loops– easy to explain/implement
GIS Design
• Disadvantages of the waterfall model
– don’t produce anything usable until late in the development process
– mistakes are often discovered late in the process
– doesn’t handle conceptual mistakes well, they are propagated throughout the process
GIS Design
• Other GIS design methods:
– Rapid prototyping• develop series of ‘throwaway’ implementations to
learn from throughout development process
• advantages: recognizes error early, unconstrained
• disadvantages: can be time-consuming and not get anywhere, confusing
GIS Design
• Other GIS design methods:
– Spiral• Cycle of acquiring, analyzing, and organizing
information in the process of going from feasibility study, requirements specification, database/application construction, and implementation
• advantages: early detection of risk, planning
• disadvantages: can be confusing
GIS Design
• Institutional GIS design failure because of the ‘people factor’– technology changes peoples work roles
– people are territorial about their work roles– people can be resistant to change– learning new skills and ways of doing things is
difficult
GIS Design• Institutional GIS design failure because of the
‘people factor’– therefore, it is very important to include users in the
GIS design process and consider training and integration of the technology as part of the design
– through needs assessment– matching users with spatial information products– make sure users are involved throughout the
development process, including early on– make sure there are plans for training