21-05-2013, 03:34 PM
WEB DATABASE INTEGRATION
WEB DATABASE.doc (Size: 200 KB / Downloads: 21)
ABSTRACT
More and more accessible databases are available in the Web. In order to provide people a unified access to these Web databases and achieve information from them automatically, a comprehensive solution for Web database integration is proposed in this paper.
Web technology has become the common user interface of choice for many information dissemination systems. Whereas, relational database management systems (RDBMS) have been the cornerstone for information warehousing for years. The integration of the two technologies has made rapid advances over the last few years. This rapid explosion has led to new challenges for information technology managers and developers. There are several competing technologies available which often do not address the issues of heterogeneous environments and web-based application development. This document addresses the challenges of designing and implementing database-integrated Web sites. Furthermore, it focuses on database-web integration difficulties in heterogeneous database environments. The technology evolved where other media such as graphics, audio, and video files can be disseminated via the web. Since there is a wealth of valuable information in databases, the integration of web sites with database technology is a natural progression of web technology. The web provides a common user interface whereas the database provides the logical structure of storing and manipulating data.
Besides the limitations of the web, there are many issues regarding database access via the web. First, the developer must choose a database interfacing technique(s). There are many proprietary solutions such as Cold Fusion, Microsoft’s ADO via Active Server Pages, etc. In addition, each major database vendor has there own web database interface solution. Oracle has its Web Developer Suite whereas Sybase has its web.sql product .This document serves as a guideline and reference for information managers and developers for addressing these issues in their respective environments.
INTRODUCTION
World Wide Web (WWW or Web) technology has grown at a phenomenal pace since its inception in 1991. The Web provides a platform independent, common user interface to information all over the world at an economical rate. Every major software vendor in the world has included some sort of Internet/Web based solution for their products ranging from support to direct interfaces to web technology.
Over the last 5 years, the Web has evolved from a file based retrieval system to an application oriented medium where users can perform purchases, query databases, or even customize their interface to various sites. This evolution has changed web developers and web masters to keep the content on web sites up to date, collect meaningful statistics on the use of the site, and empower the content owners with the maintenance of the web content.
What had to be done?
We need repository for submitted articles which can be accessed over Internet and intranet (because users of this will come from all over the world using Internet and we want to update database from our local area network).
Database should be assessable from web browser over Internet and desktop database applications (like Microsoft Access) from intranet for easy updates.
Database should provide authors all over the Internet with ability to change data about theirs articles in database after authorization, and contain all our information needed for conference.
We had limited budget which prevented us from evaluating commercial solutions.
Our project ought to be used for at least five years, so we shouldn’t choose some property solution which will cease to exist in that time-frame.
With all those points in mind, we decided to present a paper that is based on relational database with World Wide Web front end based on open-source technologies.
WEB TECHNOLOGY
The Web has become an acceptable, cost-effective information dissemination and collection tool for many businesses and organizations. Many of these entities use databases to provide web content and to collect information from their users and customers. Database driven web sites allows the web developer to provide the end user a means to access data in a logical manner rather than a file based manner. Data can be stored in a central location. Update the data in the database, the web site is then automatically updated.
This enhanced functionality of the web site does not come without a price. The web site is much more complex from administration, development, and design points of view. In order to fully understand why a database driven web sites is such powerful information tool and a complex development environment, we must understand the derivation of web technology. The web is one of many Internet services. There are other Internet services such as email, file transfer protocol (FTP), and many more...Other than email, the web is the most frequently used Internet service. The files used on the web are formatted in a standard manner called hypertext markup language (HTML). Since the web is an Internet service, it must run on the TCP/IP protocol stack. The web uses HTTP (hypertext transfer protocol) to run on top of TCP/IP. Simply, HTTP is the protocol that transports the HTML files from one computer to the next.
The end user must have a software application called a web browser to view the HTML files. The web browser interprets the HTML code and presents the information in a viewable format for the end user. Each software vendor‘s web browser interprets HTML code differently. This poses problems building consistent looks to data among different systems. The web database developer must confer with the web developer on the presentation of database content.
End User Web Server
There is a direct correlation between the growths of the Internet with Internet explosion of the PC market. In 1982, the personal computer (PC) was created. The PC provided the end user with control of his/her computing environment. The end user was empowered to process his data or information locally on his/her machine. In 1990, Windows 3.0 provided a graphical user interface (GUI) to the PC. The Windows GUI made the PC even more users friendly to use.
The web is a natural extension on the empowerment of the end user. The web empowers the end user to gain access to information locally to his/her PC. Gaining access to files was not enough. Web developers needed access to applications and programs to make their web sites and applications more powerful, thus, the advent of the common gateway interface (CGI). CGI allows the web server to connect to another program. The primary purpose of early web servers was to receive commands from the web browser (client) and serve the client HTML files. Web servers were not created to process or manipulate data. CGI gave web developers access to programming languages and applications. Web developers could write an application in languages such as C, C++, Perl, TCL, Python, and many others to perform functions that the web server could not do.
What is World Wide Web?
The World Wide Web (known as "WWW', "Web" or "W3") is the universe of network accessible information, the embodiment of human knowledge. It is basically composed of two main protocols. One of them is called Hyper Text Transfer Protocol (HTTP) and the other is Hyper Text Markup Language (HTML). HTML is language that describes appearance of text on screen (which is in fact displayed and positioned on screen by your web browser) and links or references in form of hypertext. HTTP is protocol based on TCP/IP, used to transfer HTML pages over network, from HTTP server to client’s web browser, which is in this architecture client for accessing HTTP server.
Why use relational databases?
The database is a data structure, usually rather big and stored in secondary memory, which is specialized for easy processing of large amount of different queries, and other operations among large scale of different data. There are many different database management systems (DBMS), which are used as interface between database user and computer, so user can look at his database from logical point of view, without any need to know physical way DBMS use for data storage. From that point of view DBMS can be seen as back-end CASE tool for static part of information system. Advantages that made figured relational model almost the only one used for database management today are formal foundations, complete independence of logical and physical level of database, easy way of connecting database objects at logical level etc. Relational model is consists of 2 classes of objects – relations, attributes. We can say that the attribute is atom of relational model.
WEB-DATABASE DEVELOPMENT
Web development is very simple, and yet complex at the same time. The core technology of the web is very simple due to the fact it was designed to run on any platform so long it could communicate HTML over HTTP connections. As a result, web-based client/server applications are stateless. The complexity of the development is the fact that the developer must contend with many different environments and must use crude methods to provide state to a web based application. The following sections include the basics of web-database development.
MAINTAINING STATE
One of the biggest problems when building a web based application is maintaining state. The web is a stateless, client-server application. Once the web server satisfies the web client’s (the browser’s) request, the web server has no idea the status of the client. The web server has no idea when the client has moved to another web server.
There are two techniques that the developer can use in basic HTML to build state into the connection between the browser and the web server. The server based application can set a cookie on the client’s workstation. A cookie is a small text file on the client’s machine which the web server can read. Many users disable this feature on their browsers feeling that the web administrators and web masters are using this information to track or monitor the user’s actions through the site.
DATABASE INTERFACE
The primary function of the web server to send appropriate HTML code to the web browser. Today’s trend is to serve content to the web via a database. In order to make this happen, the web server must communicate with the database. The web server must make requests to the database, interpret the database’s response, and pass on the appropriate data to the web browser.
In order for the web server to communicate with a database, it must communicate through an API (Application Programming Interface). There are many different types of database access APIs available for the developer ranging from proprietary to open standard APIs. A web database developer has many options to select the API that best meets the requirements of the project. However, the developer must be very careful in the selection of the API if he/she must support a heterogeneous environment. One API might not support all database or web servers in the developer’s environment.
Embedded SQL
Earlier there was no common function API and no standard 4GL. Embedded SQL uses a language specific Pre-compiler. SQL commands are embedded in a host programming language, such as C or COBOL. The Pre-compiler translates the embedded commands into host language statements that use the native API of the database. The problem with using Embedded SQL is that there must be a compiled version of the database interface for each database and operating system supported.
ODBC
When building a web site which must connect to many different databases, the first database connectivity standard normally considered is ODBC. ODBC is a logical choice because ODBC is a standardized API (Application Programming Interface). It is a set of function calls based on the SQL Access Group (SAG) function set for utilizing a SQL database system (back-end system). The SAG set implements the basic functionality of Dynamic SQL. Embedded SQL commands can be translated to call ODBC. Finally, there are ODBC drivers for every major database application.
OLE DB
OLE DB could be viewed as an object layer placed on top of ODBC, but Microsoft has provided direct OLE DB drivers for their database products and to de-emphasize and perhaps discontinue ODBC drivers for their products. OLE DB is not open or portable except between Microsoft OSs, which will become only a single OS - NT, in the next few years. Because of Microsoft's total control of the specification and arbitrary complexities in the facility, OLE DB is not supported by other Operating Systems - OS/2, MAC OS and various flavors of UNIX. ODBC, and Embedded SQL to a lesser degree, remain as the only open and portable interfaces for SQL accessible databases