指导文件5：毕业设计（论文）开题报告计算机科学与信息工程系（院）届题目（中文）小区物业管理系统（英文）Community Property Management System课题类型课题来源自选学生姓名专业班级指导教师职称填写日期：年月日说明：1、该表每生一份，系（院）妥善存档；2、课题来源填：“自选”或“教师指定”或“其它”，课题类型填：“理论研究”或“应用研究”或“技术开发”或“实验设计”或“其它”。
附件：毕业设计（论文）外文参考文献翻译系（院）届题目（中文）小区物业管理系统（英文）Community Property Management System学生姓名专业班完成日期：年月日目录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 indexing 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 order 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 relative 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 build 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 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 controla necessary in 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 individuals 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 doge 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 system that is Important 'is data Independence. Data-.dependence, as stated earlier. Means that applicant programs and user queries need not recognizant…physical organization of data on secondary storage. The importance of this aspect, particularly for the personal computer user, is that this greatly simplifies 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 in 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 perform 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 terms of input screen generations, output report generation etc．offered bytheses 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 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 that are used inpersonal computers．Thoroughly comprehensive andsophisticated business systems can be developed indBASh, Paradox and other DBMSs．However, theyare created by experienced programmers using theDBMS's own programming language. That is not thesame as users who create and manage personal filesthat are not part of the mainstream company system．Data security prevents unauthorized users from viewing or updating the database．Using passwords, the database, called subschema(pronounced "sub-scheme")，For example, an employee database can contain all the data about an individual employee, but one group of users may be authorized to view only payroll data, while others are allowed access to only work history and medical data.The DBMS can maintain the integrity of the database by not allowing more than one user to up-date the same record at the same time, The DBMS can keep duplicate records out of the database, for example, no two customers with the same customer numbers (Key fields) can be entered into the Data-Base.When a DBMS is used, the detailed knowledge of the physical organization of the data does not have to be built into every application program. The application program asks the DBMS for data by field pine, for example, I coded representation of "give customer name and balance due" would be sent to he DBMS．Without a DBMS, the programmer must secrecy space for the full structure of the in the program, Any change in data structure requires￡hangs in all the applications programs．The multiple-database model is represented by proposals for shared and private database architect rues, checkout and checking of data to and from shared and private databases．Each user may populates/her private database with data checked out of the shared database, perform updates against the data. and check them back into the shared Database.The multiple-database model can be used to work around" the conflict situations inherent in long lunation database sessions．Since each user from the shared database and work against. is/her private database, "disconnected" from the、hared database (at least on the surface)，the usersan avoid the conflict situations．In particular, multile users may be simultaneously updating the same thought having to wait for other users to comate late their updates．However, when updated is to benecked into the shared database, it may have to be checked in as a new version, necessitating version management. Further, 'when data in a private data-base references data in the shared data，or vice versa, a private database is not really disconnected from the shared database. For example, the evaluation of query in general will require the database system to access both a private database and the shared data-base, even if the query may have been formulated against a private database．The multiple-database model is more appropriate than the single-database model in an environment where it is easy to determine in advance logical partitions of the database that correspond to work to be performed.The single-database model has received considerably more attention than the multiple- database model．The focus of research into single-database model has been on addressing the twin problem of long waits and loss of work that the long duration of transactions brings about.The single-database model requires the intro-diction of a notion of database consistency, and protocols for concurrency control and recovery, that are different from those supported in traditionaldatabase systems．If a "reasonable" notion of database consistency is to be supported (I．c. the database system is to enforce it automatically), there are bound to be” conflict" situations where one transaction comes into an access conflict against some other transaction. If await is to be avoided，some means of a negotiated settlement of the conflict must be provided, thereby dragging the users into the details of concurrency control．The single-database model is more appropriate-ate than the multiple-database model in an environment where it is difficult to determine in advance logical partitions of the database that correspond to work to be performed, and the users closely cooperate.The objective of long-duration transactions is to model long-duration, interactive Database access sessions in application environments．The fundamental assumption about short-duration of transactions that underlies the traditional model of transactions is inappropriate for long-duration transactions．The implementation of the traditional model of transactions may cause intolerably long waits when transactions aleph to acquire locks before accessing data, and may also cause a large amount of work to be lost when transactions are backed out in response to user-initiated aborts or system failure situations．The objective of a transaction model is to pro-vide a rigorous basis for automatically enforcing criterion for database consistency for a set of multiple concurrent read and write accesses to the database in the presence of potential system failure situations．The consistency criterion adopted for traditional transactions is the notion of scrializability．Scrializa-bility is enforced in conventional database systems through the use of locking for automatic concurrency control, and logging for automatic recovery from system failure situations．A "transaction”that doesn‟t provide a basis for automatically enforcing data-base consistency is not really a transaction. To be sure, a long-duration transaction need not adopt seri-alizability as its consistency criterion．However. there must be some consistcricv criterion．Despite a large number of proposals on version support in the context of computer aided design and software engineering, the absence of a consensus on version semantics has been a key impediment to version support in database systems．Because of the differences between files and databases, it is intuitively clear that the model of versions in database systems cannot be as simple as that adopted in file systems to support software engineering．For data-bases, it may be necessary to manage not only versions of single objects (e.g. a software module, document, but also versions of a collection of objects(e.g. a compound document, a user manual，etc．and perhaps even versions of the schema of database(c.g. a table or a class, a collection of tables or classes)．Broadly, there are three directions of research and development in versioning．First is the notion ofa parameterized versioning"，that is, designing and implementing a versioning system whose behaviormay be tailored by adjusting system parameters This may be the only viable approach, in view of the fact that there are various plausible choices for virtually every single aspect of versioning．The second is to revisit these plausible choices for every aspect of versioning, with the view to discarding some of themes either impractical or flawed. The third is the investigation into the semantics and implementation of versioning collections of objects and of versioning the database schema.数据库的空间组织二十年来空间数据管理一直是数据库研究领域的活跃区，研究的焦点集中在发展存储和索引空间数据的数据结构上。
