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Evaluating different approaches of spatial database management for moving objects 2. Spatio-temporal continuum Nowadays, geographotemporal decision-making in life support sciences often requires the use of datasets where, in addition to the measured values, the description of the physical geometry (in terms of spatial and temporal coordinates) is also part of these sets. The scientific analysis of geographotemporal situations requires the introduction of
Within the spatio-temporal continuum E , space represents the order of coexistence of events, and time represents the order of their successive existence. For the continuum E to be useful in real-world TGIS applications it must be equipped with a coordinate system identifying points in space/time and a metric that measures "distances" in space/time, i.e., E : (coordinates P , metric |d P|) Generally speaking, a coordinate system is a systematic way of referring to places, times, things and events. A point in a spatio-temporal domain E can be identified by means of two separate entities: the spatial coordinates s = (s1,…,sn)ÎS ÌRn and the temporal coordinate t along the temporal axis T ÌR 1 , so that the combined space/time coordinates are p = (s , t) ÎE =S×T The above union of spatial coordinates s and the time coordinate t is defined in terms of their Cartesian product S×T. [1] 3. Integrating time in Geographic Information Systems A spatio-temporal GIS extends a customary two or three dimensional spatial GIS on the time axis. A space-time path is defined by the changes of locations over time (figure 1). In a spatio-temporal framework space and time are equivalent features of an event or a process. Furthermore each entity which physically exists in the real world is defined in a spatio-temporal context which can be conceptualized using spatial, temporal and attribute information. [2]  Fig. 1. Space and time path Every spatial object used in a GIS has a temporal validity as well as one or many attribute values. The entity of a spatio-temporal process may change its spatial representation over time as well as its spatial relationship to other entities. In addition, the related attribute information may be subject to changes throughout time. "the concept of time implies that changes occur throughout the present, the past and the future of the life span of a real-world phenomenon. A temporal GIS will aim to undrestand these changes and their affects over time rather than simply reproducing them by displaying a sequence of snapshots" (Wachowicz & Healey 1993).[2] 4. Spatio-temporal databases Spatio-temporal database is a database that embodies spatial, temporal, and spatiotemporal database concepts, and captures spatial and temporal aspects of data. Spatio-Temporal Database is a special temporal database and it has all the features of temporal databases. If we look at any timestamp only, it is almost the same as the conventional spatial database. [3] The importance of incorporating time in modeling data is widely recognized by many researches, but most of the intentions mentioned are focused around the non-spatial domain. Particularly, temporality has been studied in banking, administrative and other commercial databases. Although the underlying concept of time handling is the same, the great difference between spatio-temporal and a spatial database is what they refer to. Since spatial data are spatially referenced, the spatial topology has to be maintained in the updating process. This maintenance of topology becomes more critical when different version of an object have to be accessible, for each given of time slices, and where correctness of topology is required. Validity is one of the main concepts in spatial databases. Logically, no decision can be made when there is no valid data. If only the most recent data are kept, and out-dated ones are deleted, one can have the static database which is a snapshot of the real world (just like taking a photograph of a dynamic object). On the other hand, many spatial analysis applications do need to travel through the history of data and retain an impression about its old status. In this case, it can be seen that deleting data, even if it is non-valid, may be disastrous. In addition, many applications require estimation about the future. In this respect, one concludes that considering time as an independent dimension, which allows traveling alone the time line, is necessary. Keeping an active time domain in a spatial database, gives rise to the term spatio-temporal databases. The ideal spatio-temporal database mentioned, besides having the normal functions essential to every spatial database, also has the ability for keeping track of changed data. In such databases, the mechanism of renewing the most recent spatial and temporal topologies is implemented. In addition to the process of updating geographical objects, keeping the valid topological (either temporal or spatial) relationships are also operational. [3] Spatio-temporal objects are limited to a given temporal validity. When new information is assigned, the database has to be changed, in order to add the new data. In such a case the database may have to rebuild completely for storing the new state, which causes a great amount of redundancy. Alternatively the database might be time stamped in order to indicate the temporal validity of its objects. The ability of versioning a database is essential for all spatio-temporal applications, where knowledge of the real world is uncertain or changing through time.[2] 5. Spatio-Temporal database features There is a critical set of capabilities that are needed by moving objects database applications and Spatio-temporal database . Existing DBMS's are not well equipped to handle continuously changing data and they shoud be developed to be able to handle these data. We chose the following features for the database, that is use to manage spatio-temporal data:
With concider to above mentioned specifications, and based on the capabilities that are needed by moving objects database applications, we choose some existance DBMS's and assessed them to find best DBMS to extend it for design and development a moving object database.DBMS such as Oracle that here we mean Oracle 9i and DB2 universal dadabase that is short form of database 2 universal database and is an IBM production. SQL server version 2000 from Microsoft. And at last MySQL and PostgreSQL as Open source databases. 7. The comparison of different database software In this section we seek to compare products of a similar nature. Unfortunately this is not a simple task. It is not true that SQL Server 2000 is better than MySQL version 4.1 or Oracle 9i Database is better than DB2 Universal Database v8.1 or vice versa. All products can be used to build stable and efficient systems and the stability and effectiveness of the applications and databases depends upon the experience of the database developers and database administrator rather than the database's provider.However, each database has some advantages in comparison with others and vise versa. Here are some of the differences and similarities between different databases: 7.1. Performance comparison It is very difficult to make a performance comparison between databases. The performance of the databases depends upon the experience of the database developers and database administrator rather than the database's provider. 7.2. Platform comparison All of Oracle 9i Database, DB2 Universal Database version 8.1, MySQL version 4.1 and PostgreSQL support all known platforms, including Windows-based platforms, AIX-Based Systems, HP-UX systems, Linux Intel, Sun Solaris and so on. SQL Server 2000 only works on Windows-based platforms, including Windows 9x, Windows NT, Windows 2000 and Windows CE. 7.3. Hardware requirements To install software under the Windows-based platforms, we should have the following hardware: Table 1. Hardware comparison 
7.4. Features comparison All of Oracle 9i Database, IBM DB2 Universal Database v8.1, MySQL version 4.1 and SQL Server 2000 support the ANSI SQL-92 entry level and do not support the ANSI SQL-92 intermediate level. In general, Oracle offers all the features required for information integration in a single unified product. The inherent reliability and security features of the Oracle database are automatically inherited by information integration applications.Oracle is clearly the leader in the distributed space with its single, unified solution to satisfy a complete spectrum of information integration requirements.All editions of Oracle include; the PL/SQL engine to develop stored procedures, triggers, and functions; a Java compiler and Virtual Machine (JVM) to develop Java stored procedures and triggers; XML support; an Apache Web server; and object-relational capabilities.Oracle9i Database offers a rich set of development and administration tools, and recent releases have focused on security and scalability improvements. The implementation of various index types demonstrates how extensively Oracle9i Database focuses on fast data retrieval, especially in large databases such as data warehouses. In addition, the use of reverse key and function-based indexes, allows for a great degree in flexibility in quickly accessing data. In recognizing the high availability challenges every business faces, Oracle provides comprehensive, unique, powerful and simple to use capabilities to protect against most forms of unplanned downtime, including system faults, data corruption, human error and disaster. And, achieves this in an environment where the need for planned downtime is marginalized. IBM on the other hand has a completely different model for information integration. They offer different products for different integration scenarios. This adds several layers of complexity, since each product has to be installed and configured separately. Oracle and DB2 can scale to terabytes of data storage fairly easily. MySQL and PostgreSQL are known to run well into the hundreds of gigabytes. PostgreSQL and MySQL boast widespread use for relatively small databases (under 100GB, for example). DB2 offers the very basic set of backup and recovery capabilities but lacks the completeness and depth of data protection required by most businesses today. In fact, DB2 is behind even Microsoft SQL Server when it comes to high availability. The dialect of SQL supported by Oracle 9i Database is called PL/SQL. The dialect of SQL supported by IBM DB2 v8.1 is called DB2 SQL dialect. The dialect of SQL supported by Microsoft SQL Server 2000 is called Transact-SQL (T-SQL). The dialect of SQL supported by MySQL version 4.1 is called MySQL dialect. Transact-SQL dialect is a more powerful language than MySQL dialect. A brief comparison of PL/SQL, DB2 SQL, T-SQL and MySQL dialect follows: (Table 2) Table 2. Feature comparison 
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