数据库的空间组织外文翻译

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1、 （学校名字） 本科毕业设计（ 外文翻译 ） 题 目 小区物业综合管理系统 的设计与实现 学生姓名 专业班级 学 号 院 （系） 指导教师 (职称 ) 完成时间 Database space organization Spatial data management has been an activearea of research in the database field for two decades， with much of the research being focused on develop-ing data structures for storing and indexi

2、ng spatialdata. However, no commercial database system pro-vides facilities for directly defining and storing spa-tial data, and forniulating queries based on researchconditions on spatial data. We believe the followingare the relevant issues on which near-term researchshould be focused (in the orde

3、r of decreasing impor-tance and urgency) First, relational query optimization techniquesneed to be extended to deal with spatial queries ， thatis ， queries that contain search conditions on spatialpredicates to be developed. Second, more work needs to be done on experi-mental validation of the relat

4、ive performance of someof the more promising data structures and indexingstructures proposed thus far, with consideration of amuch broader set of operations than just a few opera-tions that have typically been used in the limited per-formance studies conducted thus far. Third, it is difficult to bui

5、ld into a single data-base system multiple data structures for spatial index-ing, and all spatial operators that are useful for awide variety of spatial applications， as such, it isdesirable to build a database system so that it will beas easy as possible to extend the system with addi-tional data s

6、tructures 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 controla necessary in

7、a multiuser 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 arsenal computers were intended for use by individual

8、s for personal information storage and process- These machines have also been used extensively small enterprises, professionals like doctors, acrylics, engineers, lawyers and so on By the nature of. intended usage, database systems on these machines except from several of the requirements of full do

9、ge database systems Since data sharing is not： Tended, concurrent operations even less so, the) fewer can be less complex. Security and integrity7aintenance are de-emphasized or absent. As data-) limes will be small, performance efficiency Is also important. In fact, the only aspect of a database sy

10、stem that is Important is data Independence. Data-.dependence, as stated earlier. Means that applicant programs and user queries need not recognizantphysical organization of data on secondary storage. The importance of this aspect, particularly for the personal computer user, is that this greatly si

11、mplifies database usage. The user can store, access and manipulate data at a high level (close to the application) and be totally shielded from the low level (close to the machine) details of data organization. We will not discuss details of specific PC DBMS software packages here Let us summarize i

12、n the following the strengths and weaknesses of personal computer data-base software systems： The most obvious positive factor is the user friendliness of the software. A user with no prior computer background would be able to use the system to store personal and professional data, retrieve and perf

13、orm relayed processing. The user should, of course, satiety himself about the quality of software and the freedom from errors (bugs) so that invest-merits in data arc protected. For the programmer implementing applications with them, the advantage lies in the support for applications development in

14、terms of input screen generations, output report generation etc offered by theses stems The main negative point concerns absence of data protection features Unless encrypted, data cane accessed by whoever has access to the machine Data can be destroyed through mistakes or maliciousintent. The second

15、 weakness of manv of the PC-basedsystems is that of performance. If data volumes growup to a few thousands of records， performance couldbe a bottleneck For organization where growth in data volumesis expected, availability of, the same or compatiblesoftware on large machines should be considered. This is one of the most common misconceptionsabout database management systems