Three-Level Database Architecture - Research Paper Example

ID # Three-Level Database Architecture Introduction It is an admitted fact that in the past few years the business organizations have started heavily relying on data and information for executing their business tasks. In order to make best use of this data they make use of different database management systems (DBMS). In this scenario, database management systems have appeared as most attractive technology based systems and trends in the modern computing. In fact, these systems are believed to be results of decades of technology based research and developments in both industry and academia. In the past, DBMSs were considered amongst the initial multi-user server systems to be built, and thus they provided an excellent support for the new developments in the form of latest systems design methods for consistency and scalability which are widely used in a number of other areas. Though, up till now a large number of researches have been carried out to propose new algorithms as well as determine the efficiency of existing algorithms for databases. However, not many researchers have taken into consideration the design and architecture of databases. The research has shown that the modern database structure is based on three level architecture (Hellerstein, Stonebraker and Hamilton; Hoffer, Prescott and McFadden 3). This paper presents an analysis of three level architecture in the context of database management systems. The basic purpose of this research is to discuss the basic scenario of three level architecture and how it forms the basis of database management systems. Three Level Architecture: Historical Perspective Database management systems are believed to be mission-critical and complex software applications and tools. At the present, modern DBMSs exemplify decades of educational and industrial research as well as influential business software development. In view of the fact that database systems were amongst the initial well developed web based server applications, hence they are considered a significant part of most of the design solutions on both sides of not simply data administration, however as well systems, networked services and operating systems. Additionally, the initial database management systems are considered amongst most powerful software applications and tools in the history of computer science, that’s why the ideas and theories invented for DBMSs are extensively copied and followed in other disciplines of computer science (Hellerstein, Stonebraker and Hamilton; Hoffer, Prescott and McFadden). In addition, for a number of reasons, the concepts regarding DBMS’s architecture and design are not as commonly recognized as they should be. In this scenario, one reason can be that the functional database systems community is reasonably small. Additionally, marketplace pushes simply support a small number of competitors at the high end of the business, hence only a small number of successful and well-known DBMSs exist. In addition, the community of people that is concerned with planning and implementation of database systems is tense for the reason that the majority of them concentrated in the similar schools, worked on the similar powerful research projects, and worked jointly on the similar profitable products. Therefore, educational treatment and efforts on database systems frequently pays no attention to architectural issues. On the other hand, theories presented in textbooks and on the internet unadventurously focus on algorithmic and theoretical aspects that are easy to educate, learn, and test regardless of a holistic argument of system structure in complete applications. However, some data are available that guides how to build up database systems, but a small portion of it has been written down or communicated generally (Hellerstein, Stonebraker and Hamilton; Hoffer, Prescott and McFadden). According to various researches, the DBMS architecture is normally divided into three views and levels: The External view The conceptual view The internal view In addition, the basic purpose of a DBMS is to provide its users with the abstract view of the database. In other words, system does not offer all features of the data, however it conceals the facts of how the actual data are maintained and stored in the database (Bhushan; Rokitskii). Figure 1Three Level Database Architecture, Image Source: (Bhushan) Three Level Architecture Objectives This section discusses the major objectives of three-level database architecture. This architecture is believed to be flexible for the reason that it allows database administrators to transform the structure of the database, without transforming or modifying the software program for example external schema. In this scenario, every database user is able to access the data according to their needs. Additionally, it does not require database users to learn about storage issues similar to indexing limitations of the database. In addition, the conceptual architecture of the database has no influence because of the transformation of the physical storage systems (Bhushan; Basics of Computer). The External Level The external level of the database three-level architecture can be acknowledged as an interface which allows the end-users to communicate with the database. Basically, it is the one that is associated with the mode in which data can be seen and used by a particular user. At the external level the DBMS provides every user with a shared or particular view or representation of their data. In this scenario, this view takes into consideration the requirements of every user and present data in the format they want to see. Additionally, there are a number of views of the information and data at this level, as well as every view is an illustration of a fraction of the whole database. However, one view permits a particular user to access their part of the database, and hides other views and features of database from them. In addition, every external view is described by means of an external representation that is composed of descriptions of a wide variety of external records found in that external view. Moreover, external level of database architecture presents different views of different illustrations of the same data. For instance one user can see the data in the format of day/month/year while another can see the same data in different format such as year/month/day (Basics of Computer; Bhushan; Rokitskii; Habela, Stencel and Subieta). Additionally, the external level of three-level database architecture is not concerned with applying any method on data to convert it into a particular format. However, this view of DBMS is basically concerned with the way data can be viewed by a particular user. In this scenario, the external level of three-level architecture can be acknowledged as particular user level. In addition, these users vary from task to task. For instance, a user can be either a system programmer or some kind of end-user. On the other hand a database administrator is normally considered as an extraordinary case. As well, the external level is composed of numerous diverse external views or outside models of the structure of the database. Each outside view explains the fraction of the database that a specific user group is concerned in as well as hides the rest of the database from that client cluster. In some cases, a number of users are able to view virtual or imaginary data that do not actually exist in the database. Basically, this imaginary data is created momentarily when it is required. For instance, marks of "C++" subject of students can be stored in the database and standard marks of this course are computed by the system when the client refers to it. In the same way, if the date of birth of a person is stored in the database then this information can be stored to calculate the age of the person without actually storing it into the database (Basics of Computer; Bhushan; Rokitskii; Habela, Stencel and Subieta). In addition, a ‘view’ can encompass data collective or computed from a number of records. In this scenario, an external record is the type of record that is observed by a specific user that is a part of his/her external view. In simple words, an external view can be considered as a collection of external records. Additionally, the external views are described by external level and these descriptions are known as sub-schemas which are written in the data definition language (DDL). Typically, the DBA is responsible for writing external schemas with the purpose of generating a user view. Every users system offers a comprehensive depiction of each kind of external record that becomes visible in that users view. Also, these external schemas are assembled through the DBMS as well as are stored in its data dictionary. The DBMS makes use of the external plans established for a particular user, with the purpose of presenting a user interface to access information and data of the database. Therefore, user interface produced throughout the external schema allows as well as exhibit details in the way that the user expects. Moreover, it as well performs certain tasks to make sure that conceal the data and information stored in the database is hidden from those users who are not authorized to access them. Normally, it conceals the internal, conceptual and physical particulars from the unauthorized users. However, in case if one user requires advanced access to the database for example with the intention of modifying the accessible record of the database then the external schema for that particular users needs to be re-written (customized) by DBA in order to allow access to him (Basics of Computer; Bhushan; Rokitskii; Hellerstein, Stonebraker and Hamilton). Moreover, external level of the three-level database architecture can accommodate a large number of user views, every user view comes with the some specific characteristics and satisfies needs of the particular user or user group for which it is designed. However, the limits, or independence or privileges assigned to a client or client groups are decided extremely cautiously. Additionally, external views are also able to accommodate several additional features such as when a user wants to see data that is not actually stored in a database or not stored at all. For instance, the phone number of a person is stored in the database. However when someone calls on their phone it might come into view that the area code for that particular user is not stored in the database, in that scenario a user would have to pick up the area or city code from the area code table (Basics of Computer; Bhushan; Rokitskii; ZeePedia; Hellerstein, Stonebraker and Hamilton). In view of the fact that the user view is the simplest entity or the interface that is used by a user in order to use the database hence it should be formed in a way that it becomes easy to use and simple to handle and self expressive, and it should be simple to navigate through. In addition, the database administrator must implement some strict security measures to ensure that a user who is not authorized to access database is not allowed to use. Additionally, the user view should be both a facilitator and a barrier for appropriate use of the database system. In this scenario, it will facilitate those people who are authorized to use a database while it will stop unauthorized people to get access to the database. However, as the system evolves it becomes feasible that a user view can modify in design, structure and the access it offers to the users. Consequently External views are intended and developed in a way that they can be customized at a later stage without making some critical changes in the internal or logical views (Basics of Computer; Bhushan; Rokitskii; ZeePedia; Hellerstein, Stonebraker and Hamilton). The Conceptual Level Conceptual level refers to presentation of the entire contents of any kind of database system. If the external view is associated with particular user levels, the conceptual level can be considered as important as a community user level. In other words, a database contains a large number of external views, in which every view is composed of an extra or less theoretical illustration of several features of the database and there will be a particular “conceptual view”, that is composed of a corresponding abstract illustration of the database as a whole. In this scenario, the conceptual level can be defined with a variety of schema that comprises a description of each variety of kinds of data or a variety of categories of conceptual record. Additionally, the conceptual model is responsible for defining data type, entities, associations, user processes and constraints on a database at the same time it hides the information of physical structure. As well, this level is usually believed to be more reliable as compared to other two views (Basics of Computer; Bhushan; Rokitskii; ZeePedia; Hellerstein, Stonebraker and Hamilton). In addition, the eventual objective of the conceptual model is to illustrate the comprehensive enterprise-not simply its data however as well how that data is utilized, how it moves from point to point inside that particular firm, why it is employed for at every point, for what purpose this data will be accessed, what technology based controls are to be implemented at every point and so on. Additionally, in the most of the existing systems the “conceptual view“ is little more than a straightforward combination of all individual external models, with the combination of specific integrity and security rules. In this scenario, this combination is made up of a variety of aspects such as all entities, their attributes and their association, data constraints, integrity and security rules, data semantic information and validation checks and measures on database to maintain data reliability and integrity (Basics of Computer; Bhushan; Rokitskii; ZeePedia; Hellerstein, Stonebraker and Hamilton). In addition, the conceptual level facilitates the external level to present the data to end-users as they required. This level mostly remains constant and the DBA designs it by carefully determining the current and prospect information requirements of the business. However, in order to expand the conceptual level of three-level database architecture, the DBA can add various objects to satisfy the varying needs of the business, without transforming or affecting the external level view of the database. Additionally, the conceptual level is described using the conceptual schema that presents a description of every conceptual record type. In simple words, the conceptual model is inclusive explanations of information of database structure for example each record type with all its fields. It as well encompasses security and integrity policy. Similar to external view, the conceptual model is also written in DDL, collected through the DBMS and stored in the data dictionary. Moreover, the DBMS makes use of the conceptual representation to produce the logical record boundary. In this scenario, it describes as well as produces the operational environment for the conceptual model to present information to end-users. In fact, conceptual model can be considered as a set of logical records (Basics of Computer; Bhushan; Rokitskii; ZeePedia; Hellerstein, Stonebraker and Hamilton). Furthermore, conceptual model also keeps and maintains the approval and verification information. In this scenario, it simply ensures that those people are able to utilize the database to whom access has been granted to make this transformation, consequently it is the job of the DBMS to examine the theoretical schema that he is certified to ensure the data or make some transformation to the data. In addition, conceptual view explains the meaning of the database; it is not altered frequently, in order to make modification to the conceptual view of the database there will be a need for contemplation which might engage modification to the other views/levels of the business or corporate database (Basics of Computer; Bhushan; Rokitskii; ZeePedia; Hellerstein, Stonebraker and Hamilton). The Internal Level The internal or physical view of database demonstrates the physical storage structure of database and file relationships used to store data on physical storage systems. In simple words, the internal view outlines how data is actually stored in the database. In this scenario, it works with the operating system (OS) and DBMS for storing and retrieving data to and from the system storage devices. In addition, the physical level is one that is directed by the OS under the instructions of DBMS, while the internal view is completely managed and instructed by the DBMS. Additionally, an internal database record is a physically stored record. Basically, it is a storage component that is extended up to the internal level throughout the stored record arrangement. In this scenario, the stored record working interface is the boundary between the physical view (used by OS) and the internal view (used by the DBMS). Though, an operating system is responsible for assigning and maintaining this interface between two levels. However, in many cases, a DBMS itself can produce this interface. The physical view interface is composed of data of database that is stored and directed by operating system. In this scenario, the OS produces the physical record arrangement to access the data from a database stored on storage systems. In addition, the internal view is demonstrated using the internal schema, which outlines how data is symbolized, how records are sequenced, what indexes would be available etc. The internal representation is written in the data definition library (Basics of Computer; Bhushan; Rokitskii; ZeePedia; Hellerstein, Stonebraker and Hamilton). Following aspects are considered in this view (Bhushan): Implementation of data encryption and compression practices Storage space provision for data and information Optimization of the internal structure Internal view is explained by means of the internal model, which does not simply describe a variety of stored record categories however as well identifies the indexes on data. Conclusion At the present, modern DBMSs exemplify decades of educational and industrial research as well as influential business software development. The basic purpose of a DBMS is to provide its users with the abstract view of the database. The system does not offer all features of the data, however it conceals the facts of how the actual data are maintained and stored in the database. This architecture is believed to be flexible for the reason that it allows database administrators to transform the structure of the database, without transforming or modifying the software program for example external schema. This paper has presented a detailed analysis of some of the important aspects of database three-level architecture. This research has explored some of the fundamental aspects related to database design and architecture. This database architecture is a standard model that holds a variety of features which can transform to update the whole database without affecting the features of another level. Works Cited Basics of Computer. Three Level Architecture of Database System. 2013. 27 April 2013 . Bhushan, Bharat. DBMS (Data Base Management System) Architecture. 31 January 2013. 25 April 2013 . Habela, Piotr, Krzysztof Stencel and Kazimierz Subieta. "Three-Level Object-Oriented Database Architecture Based on Virtual Updateable Views." FP project e-Gov. 2006. Hellerstein, Joseph M., Michael Stonebraker and James Hamilton. "Architecture of a Database System." Foundations and Trends in Databases, Volume 1 Issue 2 (2007): 141-259. Hoffer, Jeffrey A., Mary B. Prescott and Fred R. McFadden. Modern Database Management, Eighth Edition. Pearson Education, Inc., 2007. Rokitskii, R. B. "A Six-Level Architecture for Development of Internet Applications." Cybernetics and Systems Analysis, Volume 38 Issue 6 (2002): 921-925. ZeePedia. Database Management Systems. 2013. 29 April 2013 . Read More