Interoperability and the NSDI
Infrastructures are investments for steady development in the future. Spatial data infrastructures (SDIs) are such investments for a nation’s development and provide opportunities for larger use of spatial data across domains and communities for planning, monitoring and analysing projects related to development of people. Spatial data being expensive to generate and maintain, national spatial data infrastructures (NSDIs) across the world have been attempting to promote data sharing and usage. A lower cost per user removes cost inhibitions and promotes information-enabled societies and this has been the single most important motivation for interoperability of data or applications shared within any SDI.

Investment in interoperability ensures larger potential customer base and hence lower marketing cost for the data producer. It allows flexible pricing, greater opportunities for quality control and also value addition opportunities. On the consumer front, higher interoperability ensures larger choice in terms of the vendors and lower costs. Benefits of interoperability present a rationale for both long-term and short-term investments.

Interoperability itself comes in various stages and many classifications of such stages can be found in literature [1]. One such classification can be found in the study of Systems of Systems (SoS) as shown in Figure 1. The key element in the separation of the levels of interoperability is the dependence of the upper layers on the lower layers.

The Systems of Systems classification shown in Figure 1 illustrates the level of comfort in terms of interoperability achieved. These are strikingly similar to the levels of comfort achieved from syntactic and semantic interoperability (Figure 2). Such an analogy leads to the understanding that syntactic interoperability problems are closely related to technical issues where as semantic issues are rather related to organisational interoperability issues. This is only true to a certain extent because handling semantic issues are also technical in nature and not entirely organisational [2].