eXtensible Markup Language by Tahir Liaqat
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.
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