Database model - Essay Example

The data are typically organized to model relevant aspects of reality in a way that supports processes requiring this information. For example, modeling the availability of rooms in hotels in a way that supports finding a hotel with vacancies. DB’S stands for “Database Management System. ” In short, a DB’S is a database program. Technically speaking, it is a software system that uses a standard method of cataloging, retrieving, and running queries on data.

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The DB’S manages incoming ATA, organizes it, and provides ways for the data to be modified or extracted by users or other programs. Database management systems (Dobbs) are specially designed applications that interact with the user, other applications, and the database Itself to capture and analyze data. A general-purpose database management system (DB’S) Is a software system designed to allow the definition, creation, querying, update, and administration of databases. Well-known Dobbs Include Myself, Postures, Silliest, Microsoft SQL server, Microsoft Access, oracle, SAP, debase, Foxpro, IBM DUB, Libreville Base and Filmmaker Pro.

A database is not generally portable across different DB’S, but different Dobbs can inter-operate by using standards such as SQL and ODBC or JDBC to allow a single application to work with more than one database. Some DB’S examples include Myself, Postures, Microsoft Access, SQL Server, Filmmaker, Oracle, READS, debase, Clipper, and FoxPro. Since there are so many database management systems available, it is important for there to be a way for them to communicate with each other. For this reason, most database software comes with an Open Database Connectivity (ODBC) driver that allows the database to

Integrate with other databases. For example, common SQL statements such as SELECT and INSERT are translated from a program’s proprietary syntax Into a syntax other databases can understand. FORMS OF DATABASE 1 . The hierarchical structure was used in early mainframe DB’S. Records’ relationships form a treelike model. This structure is simple but inflexible because the relationship is confined to a one-to-many relationship. The IBM Information Management System (AIMS) and the 3RD Mobile are examples of a hierarchical database system with multiple hierarchies over the same data.

3RD Mobile is a eely designed embedded database for a mobile computer system. [citation needed] The hierarchical data model lost traction as Cod’s relational model became the De facto standard used by virtually all mainstream database management systems. A relational-database implementation of a hierarchical model was first discussed in schemes resurfaced with the advent of XML in the late asses[2] (see also XML database). The hierarchical structure is used primarily today for storing geographic information and file systems. Citation needed] Currently the most widely used hierarchical databases are AIMS and Windows Registry y Microsoft. [citation needed] Examples of hierarchical data represented as relational tables[edit source I editable] An organization could store employee information in a table that contains attributes/ columns such as employee number, first name, last name, and Department number. The organization provides each employee with computer hardware as needed, but computer equipment may only be used by the employee to which it is assigned.

The organization could store the computer hardware information in a separate table that includes each part’s serial number, type, and the employee that uses it. The tables might look like this: Moon First Name Last Name Dept. Mum Serial Mum Type User Moon Sally Baker 10-L 3009734-4 Computer 100 101 Jack Douglas 3-23-283742 Monitor 102 Sarah Schultz 20-8 2-22-723423 Monitor 103 David Daydreamer 20-8 232342 Printer In this model, the employee data table represents the “parent” part of the hierarchy, while the computer table represents the “child” part of the hierarchy.

In contrast to tree structures usually found in computer software algorithms, in this model the children point to the parents. As shown, each employee may possess several pieces f computer equipment, but each individual piece of computer equipment may have only one employee owner. Consider the following structure: Moon Reports 10 Director 20 Senior Manager 10 Typist Programmer In this, the “child” is the same type as the “parent”. The hierarchy stating Moon 10 is boss of 20, and 30 and 40 each report to 20 is represented by the “Reports” column.

In Relational database terms, the Reports column is a foreign key referencing the Moon column. If the “child” data type were different, it would be in a different table, but there would still be a foreign key referencing the Moon alumni of the employees table. This simple model is commonly known as the adjacency list model, and was introduced by Dry. Edgar F. Cod after initial criticisms surfaced that the relational model could not model hierarchical data. The Windows Registry is a hierarchical database that stores configuration settings and options on Microsoft Windows operating systems. . Network model Example of a Network Model. The network model is a database model conceived as a flexible way of representing as a graph in which object types are nodes and relationship types are arcs, is not restricted to being a hierarchy or lattice. . Relational model The relational model for database management is a database model based on first- order predicate logic, first formulated and proposed in 1969 by Edgar F. In the relational model of a database, all data is represented in terms of tepees, grouped into relations.

A database organized in terms of the relational model is a relational database. Diagram of an example database according to the Relational model. [3] In the relational model, related records are linked together with a “key”. The purpose of the relational model is to provide a declarative method for specifying data and aeries: users directly state what information the database contains and what information they want from it, and let the database management system software take care of describing data structures for storing the data and retrieval procedures for answering queries.

Most relational databases use the SQL data definition and query language; these systems implement what can be regarded as an engineering approximation to the relational model. A table in an SQL database schema corresponds to a predicate variable; the contents of a table to a relation; key constraints, other constraints, and SQL queries correspond to predicates. However, SQL databases, including DUB, deviate from the relational model in many details, and Cod fiercely argued against deviations that compromise the original principles. [4] 4.

Object database Example of an object-oriented model. [l] An object database (also object-oriented database management system) is a database management system in which information is represented in the form of objects as used in object-oriented programming. Object databases are different from relational databases which are table-oriented. Object-relational databases are a hybrid of both approaches. Object oriented database management systems (Dobbs) combine database capabilities with object-oriented programming language capabilities.

Dobbs allow object-oriented programmers to develop the product, store them as objects, and replicate or modify existing objects to make new objects within the DOBBS. Because the database is integrated with the programming language, the programmer can maintain consistency within one environment, in that both the DOBBS and the programming language will use the same model of representation. Relational DB’S projects, by way of contrast, maintain a clearer division between the database model ND the application.

As the usage of web-based technology increases with the implementation of Intranets and extranets, companies have a vested interest in Dobbs to display their complex data. Using a DB’S that has been specifically designed to store data as objects gives an advantage to those companies that are geared towards multimedia Some object-oriented databases are designed to work well with object-oriented programming languages such as Delphi, Ruby, Python, Perl, Java, C#, Visual Basic . NET, C++,ObJective-C and Smalltalk; others have their own programming languages. Dobbs use exactly the same model as object-oriented programming engages.

Industry Disagreement Overview[edit source I editable] While the hierarchical database model structures data as a tree of records, with each record having one parent record and many children, the network model allows each record to have multiple parent and child records, forming a generalized graph structure. This property applies at two levels: the schema is a generalized graph of record types connected by relationship types (called “set types” in CODAS), and the database itself is a generalized graph of record occurrences connected by relationships (CODAS “sets”).

Cycles are permitted at both levels. The chief argument in favor of the network model, in comparison to the hierarchic model, was that it allowed a more natural modeling of relationships between entities. Although the model was widely implemented and used, it failed to become dominant for two main reasons. Firstly, IBM chose to stick to the hierarchical model with commissioner extensions in their established products such as ‘MS and DUD. Secondly, it was eventually displaced by the relational model, which offered a higher-level, more declarative interface.

Until the early asses the performance benefits of the low-level vocational interfaces offered by hierarchical and network databases were persuasive for many large-scale applications, but as hardware became faster, the extra productivity and flexibility of the relational model led to the gradual obsolescence of the network model in corporate enterprise usage. A “database management system” (DB’S) is a suite of computer software providing the interface between users and a database or databases.

Because they are so closely related, the term “database” when used casually often refers to both a DB’S and the data it manipulates. Outside the world of professional information technology, the term database is moieties used casually to refer to any collection of data (perhaps a spreadsheet, maybe even a card index). This article is concerned only with databases where the size and usage requirements necessitate use of a database management system. [l] The interactions catered for by most existing DB’S fall into four main groups: Data definition.

Defining new data structures for a database, removing data structures from the database, modifying the structure of existing data. Update. Inserting, modifying, and deleting data. Retrieval. Obtaining information either for end-user queries and reports or for recessing by applications. Administration. Registering and monitoring users, enforcing data security, monitoring performance, maintaining data integrity, dealing with concurrency control, and reclassification’s if the system fails.

A DB’S is responsible for maintaining the integrity and security of stored data, and for recovering information if the system fails. Both a database and its DB’S conform to the principles of a particular database model. [2] “Database system” refers collectively to the database model, database management system, and database. [3] Physically, database servers are dedicated amputees that hold the actual databases and run only the DB’S and related software. Database servers are usually multiprocessorcomputers, with generous memory and RAID disk arrays used for stable storage.

RAID is used for recovery of data if any of the disks fails. Hardware database accelerators, connected to one or more servers via a high-speed channel, are also used in large volume transaction processing environments. Dobbs are found at the heart of most database applications. Dobbs may be built around a custom multitasking kernel with built-in networking support, but modern Dobbs typically rely on a standard operating system o provide these functions. Citation needed] Since Dobbs comprise a significant economical market, computer and storage vendors often take into account DB’S requirements in their own development plans. [citation needed] Databases and Dobbs can be categorized according to the database model(s) that they support (such as relational or XML), the type(s) of computer they run on (from a server cluster to a mobile phone), the query language(s) used to access the database (such as SQL or Query), and their internal engineering, which affects performance, scalability, resilience, and security.