Spatial data sharing is defined as the (normally) electronic transfer of spatial data/information between two or more organizational units where there is independence between the holder of the data and the prospective user. The transfer may be in periodic bulk-transfer, routine daily transfers, or on-line access driven by individual transactions. The participants must be separate organisations or may be departments within the same organisation. For our purpose, the distinguishing characteristic of spatial data sharing is that there be an arm's length exchange or transfer. (Calkins & Weatherbe, 1995: 66) Sharing of spatial data implies an ongoing relationship between the two participants. (Calkins & Weatherbe, 1995: 70)

The sharing of geographic information may take many forms, ranging from the sale of data by one organization to another to simultaneous access of a single data set by many persons or organisations. (Kevany, 1995: 77)

Data sharing implies an interaction between individuals or among organisations comprised of individuals. (Tosta, 1995: .201-2)

Sharing of geographic information involves more than simple data exchange. To facilitate sharing, the GIS research and user communities must deal with both the technical and institutional aspects of collecting, structuring, analyzing, presenting, disseminating, integrating, and maintaining spatial data. (Onsrud & Rushton, 1992: 1)

Data sharing presupposes a strong, long-term, funded commitment to reconcile what really constitutes different versions of the same reality. (Sperling, 1995: 391) '... process of spatial data interchange' (Sperling, 1995: 394) Sharing of geographic information necessarily presupposes the existence of relationships among individuals, organizations and / or governmental unit. As spatial databases are developed that are accessible to others than those who created them, relationships among the involved parties and societal control over the databases will be adjusted through legal mechanisms. (Onsrud, 1995: 293) Data integration [is] the ability to share access to data sources or access common databases. (Dueker & Vrana 1995: 153)

The appropriate focus for sharing data (and systems) resources is data and systems integration. Systems integration is a means by which data sharing can be achieved, and data integration is a compelling reason for sharing data. Integrating or combining data in a GIS increases its effectiveness and creates opportunities for wider enterprise benefits that accrue to entire organisations and constituencies. (Dueker & Vanra, 1995: 169)

The "data sharing" issue is much more complicated than simply determining how data created by one organization can be used by other organizations. The ability of different organizations to cooperate will determine what data is available and what technology is used. (Bamberger, 1995: 136)

'... inter-organizational information sharing is an activity that occurs within the framework of an inter-organizational alliance. Such alliances can result from a number of pre-conditions ... one organisation may hold power over another and can therefore force the subordinate organization to cooperate ... appeals to professionalism and common goals motivate organizations to ally voluntarily ... in many instances, organizations of more or less equal power status negotiate with one another to achieve an acceptable arrangement for inter-organizational cooperation.' (Obermeyer, 1995: 139)

'... spatial data sharing is in essence a problem of inventing and building a "spatial information infrastructure" of people, organizations, and technology on top of today's GIS tools, data, and operations.' (Evans & Ferreira, 1995: 454)

'... the reliability, accessibility, and feasibility of data sharing can depend on whether data are shared among multiple departments that depend upon the data to feed a divergent set of multi-user applications, or whether data are only informally shared among one department's technically able staff.