Definitions of GIS Works with geographic information Performs data input, management,...

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