英文文献数据库的空间组织.doc

英文文献 Database of space organization Spatial data management has been an active area of research in the database field for two decades，with much of the research being focused on developing data structures for storing and indexing spatial data. However, no commercial database system pro-vides facilities for directly defining and storing spatial data, and formulating queries based on research conditions on spatial data. We believe the following are the relevant issues on which near-term research should be focused (in the order of decreasing importance and urgency)．?? 　　First, relational query optimization techniques need to be extended to deal with spatial queries，that is，queries that contain search conditions on spatial predicates to be developed.??? 　　Second, more work needs to be done on experimental validation of the relative performance of some of the more promising data structures and indexing structures proposed thus far, with consideration of a much broader set of operations than just a few operations that have typically been used in the limited performance studies conducted thus far.??? 　　Third, it is difficult to build into a single data-base system multiple data structures for spatial indexing, and all spatial operators that are useful for a wide variety of spatial applications，as such, it is desirable to build a database system so that it will be as easy as possible to extend the system with additional data structures and spatial operators． If the DBMS provides a way to interactively and update the database, as well as interrogate it capability allows for managing personal data-Aces however, it does not automatically leave an audit trail of actions and does not provide the kinds of control a necessary in a multi user organization. These-controls are only available when a set of application programs are customized for each data entry and updating function.??? 　　Software for personal computers which perform me of the DBMS functions have been very popular