Articles

eXtensible Markup Language

Abstract

XML is useful as a generic data format when you want your data to be directly readable by both computers and users. XML's syntax makes data interchange easier when using known XML document types, but XML does not convey the meaning behind the data it represents, so its utility as a universal format, while better than what was previously available, is limited. These types of web technologies and web servers, offers new opportunities for the construction of grid infrastructures that are flexible and extensible. Traditional data models cannot fully support and handle the new arriving problems in transactions and especially e-business over web and desktop level, so XML taking over traditional system into it, which is used for such kind of data models, like object exchange model (OEM). Different kind of advantages and disadvantages XML has, during its work with those semi-structured technologies and different other languages, which are actually powerful languages also derived, form it. It's a revolution in web base technologies. World Wide Web Consortium (W3c) makes XML easy for the complex programs for web, its actually application and vendorindependent and easy to use.
This paper will first describe the impact of XML on data management for both well structured and more loosely structured data. Thelongest section outlines the introduction that XML does and does not address, further more about data interoperability, data integration, grids and in the end conclusion of report that tell the whole story of this paper and you may can say the outcomes of this paper.

1.0 Introduction

The abbreviation XML stands for eXtensible (Extended) Markup Language. It is markup language much like HTML. It was design to describe data. Its tags are not predefined you have to define your own tags. It provides a foundation for creating documents and it is XML that transfer documents into some thing new. By using XML, you can define the tags for your markup language. XML facilitate with method or scheme that help in storing the data or information in well structured way.
XML specification defines an XML documents as data object that confirm to the rules of well- formed document. A well formed document must meet some standards to be considered as a well formed. A well formed document is not valid until it meets the constraints define by Standard Generalized Markup Language (SGML). XML is derived from SGML; it is modified version of SGML, especially for the designed of Web documents. Even it is called as the subset of SGML. XML documents usually consist of two main parts

The prolog Version control and Document Type Definition (DTD)

The body Contain the rest of markupDTD contain the markup deceleration that that provide a grammar for a class of documents. This grammar is known as DTD. This declaration can be element type declaration, an attribute list declaration, an entity type declaration, or a notation declaration. There are two main level of XML, first it provides syntax for documents and second it provides syntax for declaring the structures of documents. Data is integrated in XML documents as strings of text, and data is bordered by text markup that explains the data [Dan Suciu 2001]. One particular unit of data and markup is called an element. XML document is made up of one or more elements. Originally designed to meet the challenges of large-scale electronic publishing, but it also provide and increasingly very important role in the exchange of a wide variety of data on the web and elsewhere [Kuchling A, 1998].

Success of XML is based upon three powerful concepts, one of them is to reusability of data in different ways secondly it provides building blocks which can be use to design new languages and finally third is to use way of encoding electronic documents in a standardized format. [Stephan Taylor 2003].

The tool of XML allows developers to create web pages and much more. It is XML that give developer a luxury to set the standards and define the information that should appear in a document, and also in what sequence. Developers and users can work with XML directly without need of any special software. XML provides very friendly environment to both programmers and the person who write the documents.

It has very fix rule for documentation that help in reading documents more easily. XML is commonly agreed-upon format for data exchanged between systems and suited to delivery and interoperability over the Web.One of the big issue for any big or small organization either it is bank or a recruitment company or a showroom or even a small company is the safety of their precious data and their valuable internal information. Using different tools for different parts of the document and allowing different users to access the data raise the security issue in system, which could cause serious problem sometimes. This particular issue is solved efficiently in XML, by limiting the access of different user up to different levels.

Every level of users has different level of access to same date with compare to the other levels. There are many problems in XML with the databases. Internet applications and the new ways in which they handle data are changing the role of database theory and its relationship with practice. Three particular problems XML have with work with databases, XML publishing, XML type checking and XML storage. XML publishing problem is a normalization problem, like relational database is normalized and at the other side XML schema is also formed into tree form, so it may conflict with the internal organizational rules. XML type checking is another problem with XML, because XML schema or DTD involve in type checking dynamically and error chances can be high by run time. XML storage is a problem because the data is labeled tree in XML format and in relational databases the data is in the tables so the problem of storing data in one or several tables is a challenge and it causes problems some times. XML defines structure based on the information being given. This allows authors to define the rules separately for displaying the XML data using Style Sheets [Iraklis Varlamis 2001]. XML give following advantages to its users with many more:1.1


1.1 Advantages of XML

Here are some good points of XML, which had made XML so popular.
Simplicity
Extensibility
Flexibility
Separation of Data and Display
Openness
Reusability of Data
Data Security

1.2 Problem with XML

XML is a flexible standard data format, but it is not the best data format for all uses and it cannot bring complete interoperability between all applications. There are many problems in XML with the databases as well. Internet applications and the new ways in which they handle data are changing the role of database theory and its relationship with practice. Three particular problems XML have with work with databases, XML publishing, XML type checking and XML storage. XML publishing problem is a normalization problem, like relational database is normalized and at the other side XML schema is also formed into tree form, so it may conflict with the internal organizational rules. XML type checking is another problem with XML, because XML schema or DTD involve in type checking dynamically and error chances can be high by run time. XML storage is a problem because the data is labeled tree in XML format and in relational databases the data is in the tables so the problem of storing data in one or several tables is a challenge and it causes problems some times. Any thing that is made by human is never perfect and it cannot be, then how than XML can be, it has some real problem in followings ways:
Documents of XML documents are really very huge they are not compact.
Standards of XML are underdevelopment so the changes are still going on.
XML business standards will prove elusive.
XML requires marshalling.

2.0 Grid Grid

Computing is a way of organizing computing resources in such a way that they are flexible, easy to access and useful in many other ways as well for users. The objective of Grid computing is to make resources available so they can be more efficiently utilized. The original purpose behind Grid computing was to link together supercomputers spread across wide distances, but the aims have since moved beyond this scope. There are many organizations, which are efficiently maintaining data grid for the help of users. The main core of these organizations is to provide the ease to the users while they are using any sort of data for any purpose. There are some predefined standard for grid. The data grid is a good example of an interoperable system. Many Grid implementations are oriented toward supplying specific types of resources. Grids can be categorized according to these resources. The most common types of Grids are Computational Grids, Data Grids, and Application Grids. There are many data grid which are currently serving a lot number of users across the world e.g. NASA Information Power Grid, AstroGrid, European Data Grid etc.Grid can be divided into two main categories the way it store data:

Structured Grid
Structured grids we always know which neighbors will be around any grid point.
Unstructured Grid
For unstructured grids the neighboring points are not immediately available.

2.1 Data Grid

The data grid emphasizes its role as a specialization and extension of the Grid that has emerged as an integrating infrastructure for distributed computation. Data grid is a subset of grid, whose basic goal is to give an integrated infrastructure for distributed computing. Access to distributed data is typically as important as access to distributed computational resources. Term Data Grid is used for different purposes:
Data Grid terms for a virtual data grid
The automation of the execution of processes is managed in virtual data grids
Data Grid terms for a distributed resilient scalable architecture
Federated server architecture refers to the ability of distributed servers to talk among themselves without having to communicate through the initiating client
Data Grid terms for an information repository abstraction

It is a software system that is used to control combinations of semantic tags and the associated value of data attributes.
Data Grid terms for a storage repository abstraction
It is a storage system that holds digital entities
Data Grid terms for a logical name space

It is a naming convention for grouping digital entities [Moore,R.W.,merzky,A., 2002].
XML is really worked hard to catch the most of capabilities that are require for distributing computing but it still have a lot of room left for improvement in these fields. XML cope well with data integration, data interoperability and grid problems. Grid is very important for heterogeneous computing.

3.0 Data Integration

The most important and recurring problem that XML able to solve is middle tire data integration. This problem is difficult for several reasons. Data coming from different sources can have different formats, and if the application code is exposed directly to these different formats. It is bad enough that a single application has to have code to handle the multiple formats [Reaz Hoque2000].
It plays a very important role in the management of heterogeneous databases. There are many different ways to integrate the individual databases. One is known as system overhaul technique in which a new system is created that consolidate the existing systems into one system. This option can be costly in some cases. The federation technique allows users to choose from the variety of individual database schemas. The composite technique, the mediated technique, the cover up technique, and the data warehousing technique the goal of all these and many more that
may come with the passage of time is and will be, the technique should be affordable, quick and easy to handled and that does not require a large amount of investment of capital and other related resources when integrating databases.
XML adopt the composite technique, the method of working of this technique is it creates a virtual data warehouse, which provides the feel of single repository, and it also allows data to remain in its natural distributing settings. XML enables intelligent client side processing; it also has the ability to change presentation of data dynamically without unwieldy and time consuming interaction with server. On middle tire XML ideally suited to address the many of persistent data integration problems that infect the enterprise application. And XML is also very good with data storage and retrieval medium.

4.0 Data Interoperability

There are many definitions available for interoperability. Many group of people look at it in different way. Ability of a system to use the parts or equipment of another system [Loesgen Dictionary 2000] or It is ability to transfer data products between different types of storage systems or share the data across different users or networks. But its function does not change with the change of word in its definition. One of the most important and fundamental feature required for distributed computing in heterogeneous environment. It gives a meaningful way for the presentation of data, and also gives permission to distribute it. XML allow data to be shared across the web not only within local network but also across the networks of the networks in a quite easy way just by giving meaningful structure to the data. It is platform independent and application independent and is well capable of mediating interactions between various Grid components. Types of interoperability
Supporting multiple devices
Enterprise:
Inter application
Inter process
Inter departmental
Inter enterprise

Here are some major achievements of XML in term of interoperability.
XML Interoperability to talk to multiple devices. Its uses SOAP to implement a pub/sub message monitor. The BizTalk initiative and how they combine to facilitate XML interchange.

Conclusion

Although XML was initially envisioned as simply a replacement for HTML, but its impact is turning out to be far grater than that. By giving a healthy affect on the client-tire, the middle-tire, and the backend-tire. It handles every tire very well that is a big plus point of XML. Different other programming languages are using XML now days due to its open end structure. Compared to the object-oriented one, the relational model is not the most appropriate for storing XML data. The only reason is when it just stores XML data then it convert into plain text, so many thing wrong can happened with it, like relations. Technology shows that there are many interesting problems concerned with the use of XML and databases together. The described use of XML and its associated technologies in databases and its importance in data warehousing, we just can not ignore XML's importance, the only thing which is needed that the future work of XML may make it, a complete data model and the work with other technologies. We can take it as semi structure data, which use Object Exchange Model for data modeling. This model actually used for semi-structure data models and use different approaches to make its use in DBMS. Using XML source for feeding data warehouse systems will become a standard in the next few years. Much of work has been done and still in progress by different people and organizations to make a maximum use of XML with other technologies. XML is brought many changes as compare to HTML; it is really flexible and extensible markup language. In the end I would like to say that XML is flourishing day by day and its use is incredibly increased during last years, because of its flexibility and extensibility. XML real deal well with the issue of data integration, interoperability and grid computing though it is not perfect in these field but progress is still continuous. For more topic on related field click ecommerce software solution