In order to realize Geo-information sharing

the first step is to share data

moreover

semantic sharing is its second and higher object. Semantic interoperability in geographic information system

which is the same as application level interoperability

is one of the available approaches to realize Geo-information semantic sharing. In this paper

status quo of interoperability and semantic interoperability in geographic information system are firstly probed into

and some existing methods to realize semantic interoperability are reviewed. Then

the new road—metadata mediator has been presented. The metadata mediator consists of semantic knowledge and rule bases

a semantic conflict finder and a coordinator. The mediator is implemented in the three-tier client/server architecture. Here

formalizing the metadata of geographic data and semantic expression of geographic information based on the formalizing method are two key tasks. By this mediator

semantic conflict can be recognized and processed

and semantic information mining also can be implemented. Furthermore

A prototype of metadata semantic interoperability

which is built according to the metadata mediator theory

is discussed

so far the prototype has shown its power in the National Resources

Environment &District Economy Information System (NREDIS).