"A Geographic Information System (GIS) is any system designed for the capturing, storing, checking, integrating, analyzing and displaying of spatially referenced data about the earth."
"A GIS is a system that allows one to combine geographic data sets, or layers, and create new, unique geospatial data to which one may apply standard spatial analysis tools."
"An organized collection of computer hardware, software and procedures designed to support the capture, editing, management, manipulation, analysis, modelling, and display of spatially referenced data for solving complex planning and management problems. A GIS is characterized by its ability to perform topological structuring of data."
"A GIS is a set of principals, methods and tools used to capture, store, transform, analyze, model, simulate and display spatial and nonspatial data. The information resulting from the whole process aims at both understanding and explaining the spatial distribution of phenomena and events, and at supporting planning decision making process" "GIS relates a location to an asset or an event. The system may be manual or computerized."
"A GIS (Geographical Information System) is any system that makes a link between statistical data and the geographic location involved. Therefore, to be fitted into a GIS, the data must include a geographical element. Either a set of coordinates (e.g. spot height, soil sample) or a link to an object that is defined in geographical coordinates (e.g. street, parcel)."
"A relational database with a sense of space."
The on-line GIS Dictionary from the University of Edinburgh has this definition, "A computersystem for capturing, storing, checking, integrating, manipulating, analyzing and displaying data related to positions on the Earth's surface. Typically, a Geographical Information System (or Spatial Information System) is used for handling maps of one kind or another. These might be represented as several different layers where each layer holds data about a particular kind of feature. Each feature is linked to a position on the graphical image of a map."
Asking GISers to define GIS brings about many other questions which were raised in the on-line discussion. One person wrote "I submit that we'll come to discover that the name of the discipline is self descriptive, and needs little or no further definition.", and in anotherresponse included, "We've been obsessing on the wrong thing. Geographic Information really IS self defining. System too, is pretty easy to define. But if you throw in the term "management"; now you've got something to wrestle with." Several posts offered the terms Geographic Information Managment and Geographic Information Science as alternatives tothe common Geographic Information System.
Some wondered if GIS could be best defined by what it can do for us rather than what it iscomposed of. It is one thing to describe hardware devices, software, and databases but it is another to relay what the components actually do within some context, how they assist in problem solving, and even what kind of problems they are used to solve. Are these integral to the 'definition' of GIS? One definition submitted included, "A GIS uses a database management system (DBMS) to store and link data that relates to the same geographic area. This facilitates the following types of queries: what if?, what is it?, where is it?, what spatial patterns exist?, what has changed since?"
Perhaps two participants summed up the discussion nicely as one wrote, "As a practitioner of GIS I find that I use many "definitions" of GIS in my work and social life and it seems never the same one twice. Maybe because I can not find one or two that suit.", while the otherwrote, "I think this debate has made it clear at least to me that even the technical communities which use GIS have their own definition and no single paragraph or concept can capture all aspects of GIS."
For further perspective on the definition of GIS, see Chrisman's disucssion at http://weber.u.washington.edu/~chrisman/G460/Lec02.html