Database

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REFERAT

Theme: Database

Plan

Introduction

1. Database model

a) Hierarchical model

b) Network model

c) Relationalmodel

d) Object-Oriented model

2. Database Management System

3. Species database

4. Databases and the WEB

Conclusion

List of used literature

Introduction

A database is a structured collection of records or data. A computer database is a kind of software to organize the storage of data. Databases help you organize this related information in a logical fashion for easy access and retrieval. To develop a database, there are several models used such as Hierarchical model, Network model, Relational model, Object-Oriented model etc. Though discussing about these models in details is beyond the level of this course unit, for the sake of completion, some models are briefed below.

In the broadest definition, a database is a collection of information. Today, databases are typically stored as computer files. A database can be a simple personal list, such as your address book, or it can be a massive list, such as New York City telephone numbers. Databases can even incorporate several lists. For example, the database for an e-commerce site, such as Amazon.com, includes inventory lists and customer lists.

1. Database model

There are several models used such as Hierarchical model, Network model, Relational model, Object-Oriented model etc. Though discussing about these models in details is beyond the level of this course unit, for the sake of completion, some models are briefed below.

a) Hierarchical model

In a hierarchical model, data is organized into an inverted tree-like structure. This structure arranges the various data elements in a hierarchy and helps to establish logical relationships among data elements of multiple files. Each unit in the model is a record which is also known as a node. Each record has a single parent.

b) Network model

The network model tends to store records with links to other records. Each record in the database can have multiple parents, i.e., the relationships among data elements can have a many to many relationships. So this model is an expansion to the hierarchical structure, allowing many-to-many relationships in a tree-like structure that allows multiple parents.The network model provide5s greater advantage than the hierarchical model in that it promotes greater flexibility and data accessibility.

c) Relational model

The relational model for the database management is a database model based on relations. The basic data structure of the relational model is a table where information about a particular entity (say, a student) is represented in columns and rows. The columns enumerate the various attributes (i.e. characteristics) of an entity (e.g. student name, address, registration _number). The rows (also called records) represent instances of an entity (e.g. specific student).We will be following the relational database model within this course and designing and using such databases will be covered within the next two sessions.

d) Object-Oriented model

In this Model we have to discuss the functionality of the object oriented Programming. It takes more than storage of programming language objects.

It provides full-featured database programming capability, while containing native language compatibility. It adds the database functionality to object programming languages. This approach is the analogical of the application and database development into a constant data model and language environment. Applications require less code, use more natural data modeling, and code bases are easier to maintain. Object developers can write complete database applications with a decent amount of additional effort. But object-oriented databases are more expensive to develop. computer database vault web

2. Database Management System

A Database Management System (DBMS) is computer. Housekeeping tasks such as updating data, deleting obsolete records, and backing up the database.

Obtaining subsets of data. software designed for the purpose of managing databases based on a variety of data models. A DBMS is a complex set of software programs that controls the organization, storage, management, and retrieval of data in a database. DBMS are categorized according to their data structures or types, sometime DBMS is also known as a Database Manager. Data management tasks fall into one of four general categories as given below:Entering data into the database.There are several advantages in DBMS such as reduced data redundancy and inconsistency, enhanced data integrity, improved security etc.

The term DBMS (database management system) refers to software that is designed to manage data stored in a database. Each DBMS typically specializes in one database model, but some DBMS software offers versatility by dealing with a variety of models and data. An XML DBMS, for example, is optimized for handling data that exists in XML format. (You'll learn more about XML later in the chapter.) An ODBMS (object database management system) is optimized for the object database model, allowing you to store and manipulate data classes, attributes, and methods. An RDBMS (relational database management system) allows you to create, update, and administer a relational database. Most of today's popular RDBMS software also provides the capability to handle object classes and XML data, making it unnecessary to purchase a separate ODBMS or XML DBMS. Today most database projects are implemented with a relational database management system. The particular RDBMS package you choose, however, depends on the scope of your project, the number of people who will simultaneously access the database, and the expected volume of records, queries, and updates. Entry-level RDBMS software, such as Microsoft Access, is a good fit for small businesses and individuals whose data can't be efficiently handled as a flat file spreadsheet.If an entry-level DBMS is located on a network, it is possible for multiple users to access the database at the same time.

As shown in Figure 11-22, each workstation typically uses database client software to communicate with the DBMS. Database client software allows any remote computer or network workstation to access data in a database. An entry-level DBMS that resides on a network server might be able to handle many simultaneous searches. However, these DBMSs are limited in their ability to deal with problems that arise when multiple users attempt to update the same record at the same time. This limited multiuser capability might be able to handle, for example, a civic center ticketing system operated by a box office clerk. It would not be sufficient, however, to handle the volume of simultaneous transactions for Ticketmaster's 6,700 retail ticket center outlets, 21 telephone call centers worldwide, and online Web site. In situations with many users who make simultaneous updates, it is usually necessary to move to database server software, such as Oracle Database, IBM DB2 Universal Database, Microsoft SQL Server, Sun Microsystem's open source favorite MySQL, or public domain SQLite. Database server software is designed to manage billions of records and several hundred transactions every second. It provides optimum performance in client/ server environments, such as LANs and the Internet. It can also handle a distributed database, in which a database is stored on several computers, on multiple networks, or in different geographical locations. As shown in Figure 11-23, database server software passes query requests from client software to the database and sends query results back to the client.

3. Species database

A relational database

A relational database stores data in a collection of related tables. Each table is a sequence of records, similar to a flat file. All the records in a table are of the same record type. Each row of a table is equivalent to a record. Each column of the table is equivalent to a field. A relational database typically contains several tables. In a relational database, relationships are specified by joining common data stored in the fields of records in different tables. For example, most albums contain many tracks, an example of a one-to-many relationship. The Vintage Music database stores general information about an album in one table and information about individual tracks in another table. The way a relational database establishes relationships allows the tables to be essentially independent, but the tables can be joined for a particular task as required. Relationships can be added, changed, or deleted on demand, making this database model very flexible. The relational database model's flexibility is a major factor in its use for the majority of databases that handle the everyday query and reporting needs of businesses, government agencies, and organizations.

A dimensional database

A dimensional database, sometimes referred to as a multidimensional database, organizes relationships over three or more dimensions. Each field is contained within a cell that can be accessed directly from a query or from following a relationship. Dimensional databases are an extension of the relational database model in which tables are stacked in addition to being linked side by side. Compared to a relational database with complex queries based on relationships and joins, a dimensional database offers a simpler way to visualize data and formulate queries. Dimensional databases are easy to maintain and efficient to use because data is stored in the same way as it is viewed. However, formulating and populating a dimensional database requires more expertise than a relational database. Consequently, dimensional databases are most often deployed for data analysis and decision support systems in which data from operational databases is moved into a dimensional data warehouse before being queried by managers.

An object database

An object database, also referred to as an object-oriented database, stores data as objects, which can be grouped into classes and defined by attributes and methods. The Programming chapter covers object-oriented terminology in detail; but in the context of object databases, a class defines a group of objects by specifying the attributes and methods these objects share. The attributes for an object are equivalent to fields in a relational database. A method is any behavior that an object is capable of performing. For example, Vintage Music Shop has to keep track of objects that represent customer orders. To set up an object database for this task, the first step would be to define a class called Orders that can hold data such as the order number, order date, customer number, and albums ordered. A method called Check Inventory can be defined for this class. Its job is to make sure the album is in stock. Object databases excel in representing objects that have slightly different attributes, which is the case in many real-world business applications. Suppose that Vintage Music Shop accepts phone orders and Web orders. These two types of orders differ slightly because an e-mail address is used to communicate with Web customers, whereas a telephone number and order clerk name need to be recorded for customers who order by phone. A relational database would require two record types, but an object database can be set up so that the Orders class has two derivative classes, one for Web customers and one for phone customers.

The object database model is newer than the relational model and has not yet gained a substantial foothold in mainstream database applications. Its advocates, however, cite advantages over rival database models, including the idea that object databases best reflect real-world entities and relationships.

The object-relational database

The term object-relational database is used to describe a variety of technologies that combine object-oriented and relational concepts. The object-relational database model has been described as an attempt to add object-oriented characteristics to tables. Basically, an object-relational database is organized as one or more tables, just as in a traditional relational database. Objectrelational databases, however, have the flexibility to store unique types of data and program code necessary to access that data. To understand the distinction between relational databases and objectrelational databases, suppose you restructure your iTunes playlist as a table in a relational database containing fields for the song title, artist, time, and so on. The database does not actually contain the .m4p data for the song, but it probably contains the name of the computer file that holds the song. When you select a song to play, the database doesn't play it. Instead, the file name is passed to your iTunes jukebox, which plays the song. In contrast, you could use an object-relational database to store the actual digital data for songs in a field called SongFile. Your database could also hold a routine called PlaySong. If you select the database record for “Blue Suede Shoes,” for example, the database uses its PlaySong routine to play the data stored in the SongFile field, so there is no need to use external music player software (Figure 11-16). Most of today's relational database tools offer object-oriented features. For example the popular database query language SQL, which you'll learn about later in the chapter, can be used to define custom functions to process the data in a database. However, object-relational hybrids do not typically support a full set of object-oriented characteristics. The distinction is somewhat technical. Suffice it to say that database models are still evolving as the best elements are blended and optimized to meet the needs of today's complex database applications.

4. Databases and the WEB

The Web allows access to many databases. When you shop at an online store, for example, the photos, descriptions, and prices you see are pulled from the merchant's database and displayed as Web pages. More direct database access is offered by online card catalogs, such as the U.S. Library of Congress.

A database also provides the foundation for online access to course registration systems, yellow pages, real estate listings, movie reviews, flight schedules, and a host of other information. The Web provides both opportunities and challenges for accessing the information in a database. Obviously, with its global reach, the Web provides an opportunity for many people to gain access to data from multiple locations. Web access is constrained, however, by the stateless nature of HTTP and the necessity to provide access by using a browser as client software. Providing access to databases over the Web requires some tricks. It does not, however, require special databases or special DBMS. The advantages of static publishing include security and simplicity. Your data remains secure because you have not provided direct access to your database, so unauthorized users cannot change your data. Each time regular customers at Vintage Music Shop connect to the site, they see Web pages tailored to their music preferences. Country music fans, for example, see descriptions of Nashville classics and a list of discount albums by their favorite artists. Obviously, these pages cannot be the result of static publishing. They are created by a dynamic Web publishing process that generates customized Web pages as needed, or “on the fly.” Dynamic Web publishing relies on a program or script, referred to as a server-side program, that resides on a Web server and acts as an intermediary between your browser and a DBMS. In the Vintage Music Shop example, a server-side program reads a cookie from the customer's computer to find the unique number assigned to the customer. The server-side program then uses the customer number to generate a query, which is sent to the database server software. This software accesses the database to locate the customer's music preferences and favorite artists. The serverside program then asks the database server software to locate all the specials that apply to this customer's preferences. A list of applicable albums, descriptions, and prices is sent back to the Web server, where it is formulated as an HTML document and sent to the browser.

Conclusion

A database is an organized collection of data. It is the collection of schemas, tables, queries, reports, views, and other objects. The data are typically organized to model aspects of reality in a way that supports processes requiring information, such as modelling the availability of rooms in hotels in a way that supports finding a hotel with vacancies. An in-memory database is a database that primarily resides in main memory, but is typically backed-up by non-volatile computer data storage. Main memory databases are faster than disk databases, and so are often used where response time is critical, such as in telecommunications network equipment.SAP HANA platform is a very hot topic for in-memory database. By May 2012, HANA was able to run on servers with 100TB main memory powered by IBM. The co founder of the company claimed that the system was big enough to run the 8 largest SAP customers. An active database includes an event-driven architecture which can respond to conditions both inside and outside the database. Possible uses include security monitoring, alerting, statistics gathering and authorization. Many databases provide active database features in the form of database triggers.

Data warehouses archive data from operational databases and often from external sources such as market research firms. The warehouse becomes the central source of data for use by managers and other end-users who may not have access to operational data. For example, sales data might be aggregated to weekly totals and converted from internal product codes to use UPCs so that they can be compared withACNielsen data. Some basic and essential components of data warehousing include extracting, analyzing, and mining data, transforming, loading, and managing data so as to make them available for further use.

List of used literature

1. Anderson, Laurence. “History of Mac OS.” Amacgenius.com 1 November 2005. Available from: http://amacgenius.com/archive/125/.

2. Coustan, Dave, and Curt Franklin. How Operating Systems Work. How Stuff Works, Inc., 2005. Available from: http://computer.howstuffworks.com/operating-system.htm. “IT Facts for OS.” Available from: http://www.itfacts.biz/category/os.

3. What is Linux? Linux Online. Available from: http://www.linux.org.

4. Craig Van Slyke Information Communication Technologies: Concepts, Methodologies, Tools, and Applications (6 Volumes). ISBN13: 9781599049496, 2008, Pages: 4288

5. Lorenzo Cantoni (University of Lugano, Switzerland) James A. Danowski (University of Illinois at Chicago, IL, USA) Communication and Technology, 576 pages.

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