Study On GML Documents Oriented Access Control Model For Spatial Data

Geographic Markup Language proposed by Open Geospatial Consortium is an encoding specification based on XML for geographic information. GML has received extensive attention and support for it is platform-neutral. Some mechanisms are needed to protected sensitive spatial information stored in GML documents, and access control is one of the mechanisms. Access control ensures legitimate users access to legal resources, and restrict to non-authorized users to access system. The research of GML documents oriented access control model will have an important theoretical and practical meaning for improving spatial data security, as well as providing indemnity of spatial data sharing.The target of this study is to design a flexible model based on the the regionality and multi-scale of spatial data. This model should provide the fine-grained and content-based access control, the efficiency should also be considered.This paper first introduces and analyses the characters of GML document,the GML schema and its/related technology, then researches the access control model in detail and chooses RBAC model as the base of this research.Through the above analysis, a GML documents oriented access control model RORBAC is proposed. This model improves RBAC model to enforce a multi-grained access control for GML documents.The idea of GML schema permission, GML instance permission and GML region permission are put forward and the exact definitions of each concept are also advanced. And then access permissions, propagation of authorization and conflict policy are discussed.To improve the efficiency of authority, a unified index for GML data is designed to improve the efficiency of authority. This index extends R-tree index with using the Zhang coding as index entries.Based on the researches above, the author design and implement a prototype system based on the proposed access control model. This system adoptes a unified access control specification language according to XML criterion to specify the policy of access control. The research test proves that the model's design idea is reasonable and applicable, and the expected goals and requirements are basically achieved.