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Scale is an important factor when people acquire laws of geographical phenomena and processes. Generalized scale
includes not only spatial scale and time scale but also semantic scale in geographic information science. Semantic scale
describes semantic change amplitude and hierarchy of attribute contents of geographic entities. Semantic change
amplitude represents attribute character changes in the unit time, the while hierarchy means classification and rank of
attribute description. Scale is in inverse proportion to detailed degree of geographic entities when GIS displays
multi-scale geographical spatial data. It is difficult that existing GIS display features of different semantic scale. As for
the classified or ranked geographical spatial data the optimal solution is the hierarchy or rank of geographic entities
displayed is higher when scale becomes small, so the generalization degree of detailed feature is higher.
Ontology is a kind of modeling tool of concept model that is able to represent information system at the semantics and
knowledge level. Geoontology is a kind of domain ontology and offers glossaries and relationships among concepts in
the geographic spatial information domain. As far as the geographical hierarchy and classification system is concerned
the relationships among the geographical concepts is hierarchy relationship, namely the relationship between the parent
concepts and the child concepts or between hypernyms and hyponyms. Geoontology can represent formally this
hierarchy relationship. A geographical concept can be navigated to its parent concept or child concept, and implements
the automatic generalization of geographic spatial data by merging the features in the geographical feature classes
corresponding to all child concepts of the some geographical concept in geoontology. However the automatic
generalization method based on the geoontology cannot smooth the linear features and the boundary of polygon features,
which should be implemented by resorting to other automatic generalization algorithms.
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