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Introduction to XML

XML--- extensible markup Language --- is an exciting development in web technology. It is the youngest and most comprehensive of markup Language. (Markup refers to any thing on a document that adds special meaning to a particular text; for example, bold text is a form of markup). This language got the name Extensible Markup Language from the characteristic that is not restricted to fixed set of tags, as is HTML (Hypertext Markup Language). An XML user creates his own tags according to need. A tag is a sequence of characters in a markup language used to provide information, such as formatting specifications, about a document.

Markup languages are roughly classified into three types:

•Stylistic ----- defines character presentation; for example bold, italics, underline, font etc. •Structural ----- define the structure of the document as for heading and paragraph. •Semantic ----- informs us about the content of the data, like giving a title.

SGML (Standardised Generalised Markup Language) is the mother of all markup languages and has been in existence since the late 1960s. In 1986 it becomes an international standard for defining the markup languages. It is used to create other languages, including HTML, which is very popular for its use on the web. HTML was made by Tim Berners Lee in 1991. While on one hand SGML is very effective but complex, on the other, HTML is very easy but limited to a fixed set of tags. This situation raised the need for a language that was as effective as SGML and at the same time as simple as HTML. This gap has now been filled by XML.

The development of XML started in 1996, when a team led by Jon Bosak of sun Microsystems began work on a project for remoulding and cutting the inessential parts of SGML. They took the best of SGML, guided by the experience with HTML, and produced something that was no powerful, but much simpler to use. The World Wide Web Consortium also contributes to the creation and development of the standard for XML. The specifications for XML were laid down in just 26 pages, compared to the 500+ page specifications that define SGML.

Although, XML looks like HTML, there is a world of a difference. While HTML specifies what each tag and attribute means and how the text define by it will look in a browser, XML uses the tag only to delimit pieces of data, and leaves the interpretation of the data completely to the application that reads it. For example, if we see "" in an XML file, it may or may not mean bold (as in HTML) ---- it may mean 'book', 'bank' or anything else specified by the programmer. HTML is only a presentation technology ----it carries no description of the content held within its tags ----whereas in XML a programmer can describe the text in its own tag. Moreover we can specify the importance of a tag in XML so that a hierarchy of data can be represented, which is not possible in HTML.

Like HTML, both Netscape and Microsoft browsers support XML. As XML files are text files, it becomes easier for a programmer to debug application. But at the same time, being in a text format, XML files are always larger than comparable binary formats. XML is a family of technologies. XLINK is one of them, which describe a standard way to add hyperlink to an XML file. XPOINTER and XFRAGMENTS are syntaxes for pointing to parts of an XML document. XSL is an advanced language for expressing style sheets. We can also use cascading style sheets (CCS) as we do in HTML. XML NAMSPACE is a specification that describe how to associate a URL wit every single tag. XML SCHEMAS help to define the XML-based formats.

DOM is a standard set of function called for manipulating XML files from a programming language. Math ML is a describing mathematic as a basis for machine communication. With adequate style-sheet support would ultimately be possible for browsers to natively render mathematical expression, which is not possible in HTML. XML encryption is a process name for encrypting and decrypting digital content. XML signatures provide integrity, message authentication for data of any type. These things are extensively used for providing security in applications.

XML protocol used to develop technologies that allow two or more peers to communicate in distributed environment, using XML as its encapsulation language. Nowadays we can find a number of quality sites made by using XML. Use of XML can also be seen in B2B portals and it is also used in WAP development. WML (Wire-less Markup Language) is derived from XML, which plays the primary role in the development of WAP application.

The most novel features of XML is that it is able to express complex data structure, and even distributed action, in terms of simple, punctuated stream of text. Any network component newer than the Abacus can send and receive XML; almost any processor has sufficient power to parse it. XML is license free, platform independent and well supported. Visual Studio .NET, Hailstorm, .NET platform, latest products from Microsoft, are fully compatible with XML.

Many companies are using this language according to their needs. As this language can be used for various objectives, it can be seen on various platforms, in combination with different languages. XML is a key to the next-generation Internet, offering a way to unlock information so that it can be organised, programmed and edited ----a way to distribute data in more useful ways to variety of digital devices and allowing web sites to collaborate. Today XML is a young child developing various aspects of its personality; which of these would be the dominating trait to give it its final adult character could be anybody's guess.

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Beginning XML - Part IV(Basic Schema Of A DTD)

In the following two articles, I'm going to wrap up my pondering on XML. We'll explore the basic schema of a DTD, and the future of XML.

Let's recall that some basic features of XML are:

· XML can keep data separated from your HTML · XML can be used to store data inside your HTML documents · XML can be used as a format to exchange information · XML can be used to store data in files or in databases

The power and beauty of XML is that it maintains the separation of the user interface from structured data, allowing the seamless integration of data from diverse sources. Customer information, purchase orders, research results, bill payments, medical records, catalog data and other information can be converted to XML on the middle tier, allowing data to be exchanged online as easily as HTML pages display data today. Data encoded in XML can then be delivered over the Web to the desktop. No retrofitting is necessary for legacy information stored in mainframe databases or documents, and because HTTP is used to deliver XML over the wire, no changes are required for this function.

Once the data is on the client desktop, it can be manipulated, edited, and presented in multiple views, without return trips to the server. Servers now become more scalable, due to lower computational and bandwidth loads. Also, since data is exchanged in the XML format, it can be easily merged from different sources - ok, this is the aspects that personally interests me. The portability of data. Database programmer all over the world face unlimited problems while tackling with data of multifarious formats. If formats cease to matter, anybody, anywhere, on whichever machine, can view and manipulate the data.

>From the previous article, we might recall the XML, unlike HTML, does not have proprietary tags. We can go on a wild trip and define our own tags, according to the necessity. Consider this for example:

<?xml version="1.0"?> <my-schedule> <date>4/17/2001</date> <morning-to-noon> <XML-tutorial> <XML-Introduction>Telling what exactly XML means</XML-Introduction> <XML-Examples>Some Examples of XML</XML-Examples> <XML-Conclusion>Some concluding text</XML-Conclusion> <XML-Email>Email the XML files to Yagna</XML-Email> </XML-tutorial> </morning-to-noon> <noon-to-mid-noon> <nothing-important> Have something light to eat and laze around </nothing-important> </noon-to-mid-noon> <mid-noon-to-evening> <work>Work on a client's web site</work>

</mid-noon-to-evening> ............ <date>4/18/2001</date> .............. </my-schedule>

If you can't make out what this is all about, don't worry. This is just an imaginary schema of a data structure that can be represented through an XML document.

Before you get the time to come to grips with the gory XML introduction, I present a more evolved version of the above mentioned XML code:

<?xml version="1.0"?> <!DOCTYPE my-schedule [ <!ELEMENT my-schedule (date +)> <!ELEMENT date (morning-to-noon, morning-to-mid-noon, mid-noon-to-evening)> <!ELEMENT morning-to-noon (XML-tutorial)> <!ELEMENT XML-tutorial (XML-Introduction, XML-Example, XML-Conclusion, XML-Email)> <!ELEMENT XML-Introduction (#PCDATA)> <!ELEMENT XML-Example (#PCDATA)> <!ELEMENT XML-Conclusion (#PCDATA)> <!ELEMENT XML-Email (#PCDATA)> <!ELEMENT noon-to-mid-noon (nothing-important)> <!ELEMENT nothing-important (#PCDATA) <!ELEMENT mid-noon-to-evening (work +)> <!ELEMENT work (#PCDATA) ]> <my-schedule> <date>4/17/2001</date> <morning-to-noon> <XML-tutorial> <XML-Introduction>Telling what exactly XML means</XML-Introduction> <XML-Examples>Some Examples of XML</XML-Examples> <XML-Conclusion>Some concluding text</XML-Conclusion> <XML-Email>Email the XML Article</XML-Email> </XML-tutorial> </morning-to-noon> <noon-to-mid-noon> <nothing-important> Have something light to eat and laze around </nothing-important> </noon-to-mid-noon> <mid-noon-to-evening> <work>Work on a client's web site</work>

</mid-noon-to-evening> ............ <date>4/18/2001</date> .............. </my-schedule>

The above is a comprehensive example of a DTD - Document Type Definition. XML provides an application independent way of sharing data. With a DTD, independent groups of people can use a common DTD for interchanging data. Your application can use a standard DTD to verify that the data you receive from the outside world is valid. You can also use a DTD to verify your own data.

In this example, the data structure is well defines. Each parent node has a child node, and some child-nodes have grand-child nodes and so on.

Amrit Hallan is a freelance web designer. For all web site development and web promotion needs, you can get in touch with him at http://www.bytesworth.com. For more such articles, visit http://www.bytesworth.com/articles and http://www.bytesworth.com/learn You can subscribe to his newsletter [BYTESWORTH REACHOUT] on Web Designing Tips & Tricks by sending a blank email at bytesworth-subscribe@topica.com

Beginning XML - Part III (Building Blocks)

XML documents (and HTML documents) are made up by the following building blocks:

· Elements · Tags · Attributes · Entities · PCDATA · CDATA

This is a brief explanation of each of the building blocks:

Elements

Elements are the main building blocks of both XML and HTML documents.

Examples of HTML elements are "body" and "table". Examples of XML elements could be "my-schedule" and "date". Elements can contain text, other elements, or be empty. Examples of empty HTML elements are "hr", "br" and "img".

Tags

Tags are used to markup elements.

A starting tag like <element_name> mark up the beginning of an element, and an ending tag like </element_name> mark up the end of an element.

Examples:

A body element: <body>body text in between</body>. A message element: <message>some message in between</message>

Attributes

Attributes provide extra information about elements.

Attributes are placed inside the start tag of an element. Attributes come in name/value pairs. The following "img" element has an additional information about a source file:

<img src="computer.gif" />

The name of the element is "img". The name of the attribute is "src". The value of the attribute is "computer.gif". Since the element itself is empty it is closed by a " /".

PCDATA

PCDATA means parsed character data.

Think of character data as the text found between the start tag and the end tag of an XML element.

PCDATA is text that will be parsed by a parser. Tags inside the text will be treated as markup and entities will be expanded.

CDATA

CDATA also means character data.

CDATA is text that will NOT be parsed by a parser. Tags inside the text will NOT be treated as markup and entities will not be expanded.

Entities

Entities as variables used to define common text. Entity references are references to entities.

Most of you will known the HTML entity reference: " " that is used to insert an extra space in an HTML document. Entities are expanded when a document is parsed by an XML parser.

The following entities are predefined in XML:

Entity References Character

< means "less than - < " > means "greater then - > " & means "ampersand - & " " means "quotes - " " ' means "apostrophe - ' "

Since, right now we do not plan to go very deep into XML coding, we'll leave the data definition here, and move the future implication of XML.

Extensible Markup Language (XML), which complements HTML, promises to increase the benefits that can be derived from the wealth of information found today on IP networks around the world. This is because XML provides a uniform method for describing and exchanging structured data. The ability to describe structured data in an open text-based format and deliver this data using standard HTTP protocol is significant for two reasons. XML will facilitate more precise declarations of content and more meaningful search results across multiple platforms. And once the data is located it will enable a new generation of viewing and manipulating the data.

Consider an industry where interchange of data is vital, such as banking. Banks use proprietary systems to track transactions internally, but if they use a common XML format over the Web, then they'd be able to describe transaction information to another institution or an application (like Quicken or MS Money). Of course, they'd also be able to present the data in a pretty Web page. FYI: This markup does exist. It's called OFEX, the Open Financial Exchange format.

Under certain circumstances, if IE 4 on the PC comes across a <SOFTPKG> tag with the proper contents, a function is started that gives a user the opportunity to update installed software. If you're using Windows 98, it's possible that you've seen this process in action without knowing it was an XML application.

Content Creation - How To Articles: they include detailed step by step instructions. Examples: how to publish your e-zine, how to promote your business, how to attract visitors to your web site.

Content Writing Companies - Content is king for one reason: People surf for content. Each of the major search engines is only successful to the extent that it helps people find the web site content they are looking for. Whichever search engine helps people find that web site content the quickest becomes the most popular. The more popular the search engine is, the more money it makes from advertising.

Xml Dynamic Content - Thousands of articles are published daily and immediately become shareware for those who enjoy the privileges of using them as content on their web sites, in e-zines, blogs etc. The downside for some authors is that many such articles are stolen and re-published under the thieves own names and copyright notices.

Content Building - The trend of SEO has changed recently. Many of the sites have realized that search engines crave for good and original content...... The age old method of site linking has taken a back seat. Quality content has become the latest mantra for increasing the page rank by many web sites. Its not like web sites have stopped link exchange but they have started giving more preference to content building.

Google News - Content is what Search Engine robots look for when they decide how high to rank a web site for certain keywords. Let's define what we mean by content. To a search engine, content includes words, sentences, and paragraphs that are FULL of the keywords that you want to be found for. Please understand that all graphics are totally ignored by the search engines.

Blogging Builds Credibility - Blog is short for the word weblog. A weblog is a journal (or newsletter) that is frequently updated and intended for the consumpution of the general public. Blogs generally represent the personality of the author or the Web site.Blogs can be used in the business world as well. It is a concept that started in late 90s. It used to be a way to comment an existing webpage, an opportunity for visitors and readers to react or voice out ones opinion on the said page.

Free Traffic - RSS Feeds are the latest in cutting-edge tools for alert webmasters. Globally, consumers are gobbling up this latest trend. The convenience of being able to monitor all of their favorite feeds in one place carries tremendous appeal. Webmasters and marketers find RSS feeds equally as attractive.

Blogging Ad Placement - Where should you put the ads on your blog so you make more money?

Rss Feeds Article - Blog is short for web log and became popular during the 2004 Presidential Election as weblog writers all over the world opined and investigated both the president and John Kerry. There are literally hundreds of thousands of blogs out there.

Internet Online Business - Blog is short for weblog. A weblog is a journal (or newsletter) that is frequently updated and intended for general public consumption. Blogs generally represent the personality of the author or the Web site.

Dynamic Website Content - If you are like most internet surfers, you will spend much of your time hanging around web sites with dynamic web site content, or content that is updated constantly or personalized to your preferences. The age of static, archival web sites is long gone, in in its place is a dynamic and powerful internet driven by PHP, ASP, CGI, and Java.

Content Hungry - 1. One of the best ways to generate no cost traffic is by submitting ready-made articles to "content hungry" web-site and newsletter publishers with your "resource box" attached. A resource box is nothing more than a little 3-6 line "bio" about you and/or your web-site - including a link to your site (or even instructions on how to subscribe to your newsletter)...

Online Blogging - Blogging can be used as a personal journal or as a space for like-minded people to come and collaborate, bouncing ideas off of each other. Online blogging can also be used for personal rants and journalistic critiques, to collect things such as recipes or to register memos to one's family.

Blogging Community - Blogging for dollars might sound like the latest game show or some new drinking game, but it's the latest craze to hit the Internet. Bloggers began blogging for a number of reasons, but as the weblog movement has increased in popularity, they have found ways to monetize their blogs and are seeing their commitment pay off.

Blogging Subject - Blogging gets its name from the term 'blog', itself a short form of 'weblog', which again is a blend of two words, 'web' and 'log'. A weblog is a repertoire of web publications stored in reverse chronological order, which means that a new entry comes on top of the one just preceding it. Anyone who looks after a weblog , writes for and maintains it is said to be 'blogging'. Blog-posts are articles posted on a weblog by a 'blogger'.

Content Based Web Site - A fast and easy way to accomplish all of these goals is by using content syndication. Content syndication is the simple process of making a block of content (which usually changes on a regular basis) available for other webmasters to use on their web sites.

Content Article - If you are like most online article authors and then you know the best way to get your articles online and out into distribution is to use a very well trafficked online article submission web sites. Other web site owners will pick up the content for their web site and leave the byline with the links to your web site on the bottom of the articles.

Start Blogging - Blogging has captured the interest of many across the World Wide Web. The cold, robotic nature of the virtual world becomes warm and cozy when we see personality and real life thoughts appearing on our screens. Sometimes we make a connection with the blogger that leaves an impression. We're caught! Our natural curiosity will draw us back on a regular basis to get the juicy updates the blogger throws our way.

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About the Writer of this Article

Beginning XML - Part IV(Basic Schema Of A DTD)

Beginning XML - Part III (Building Blocks)