eXtensible Markup Language (XML)
XML – eXtensible Markup Language:
The programming arena, has really changed since it was first established, many people today are looking to learn new exiting things, which can help them, with the everyday chores of life
It is also imperative for programmers, to continue to grow in the programming arena, and to never give up, so that they can become great programmers, and change the world around them
In today’s article, we are going to be talking about The Extensible Markup Language (XLM) and, this language purpose, in the programming arena
Introduction
The number of users of XML standards today is large and that number keeps growing as new developers and programmers gain more experience, in the technology industry and pick a career doing programmingX
XML has the ability to be a fully portable, platform-independent and self-descriptive
Machines have a hard time reading human language; therefore, programmers use XML, as a way of transmitting information, from humans, to machines
XML is defined as the set of rules that encode documents in a form that machines can read
Generality, simplicity and usability on the INTERNET was the emphasis and the goal when designing XML
As a simple, meta-language and flexible text formatting programming language, XML was part of the results of Standard Generalized Markup Language: SGML (ISO 8879)
XML is simple, because the tags are not pre-defined, it is a meta-language, because other languages are derived from it, and it is a flexible text format, because text can be formatted freely into any other language using XML
The XML programming language, came into the picture due to mainly, publishing reasons, on cyberspace
Large scale electronic publishing had a need to transport data over the INTERNET, therefore, developers had to figure out a way to solve this problem
XML conquered that problem in the eye of many developers online
XML also allowed large data to be transported over the INTERNET without putting too much work on the network and causing the network to slow down
This is the reason why the role of XML in the exchange of a wide variety of data, which gets transported over the INTERNET, has an increasingly important role in the cyber world
XML is a document formatted language, which is used to format many World Wide Web pages, that is why it is an extensible markup language
XML has grown in popularity, since it was first erected, and many people have a lot of respect for this tool, because it is easy to use and very efficient
XML History
The development of XML began in the 1990s; Emails and weekly teleconferences was the way of communication, which developers utilized to design XML in twenty week
The first draft of XML was released after those twenty weeks which ran from July to November 1996 and involved a lot of hard work and major decisions to make
The development of XML, did not come easily, but it was completed, and today we can say, that we have an advanced tool available, to transmit data online
One of the reasons why XML was created
HTML (Hypertext Markup Language) did not have the ability to create new functions and modify existing ones
Unfortunately the HTML version that was available at the time, could not extend systems, because it restricted the definition of new text elements
XML implementation does not forget and considers the future growth of systems, which makes it useful to many developers
Its systemic measure and its ability to extend a system, makes XML a powerful tool
Also the level of effort required to implement the extension, makes it an easy to use language for many developers, who wish to use this tool
The modification of existing functionalities and the addition of new ones are some of the extensions that XML can add to systems
In February 10, 1998 W3C recommended XML 1.0 as a standard for markup language after the designing of XML which continued in 1997
The history of Extensible Markup Languages (XML) started the same time that Standardized Generalized Markup Language (SGML) began their development
In the 1970s while working at IBM a group of developers started the development of XML, these developers were Charles Goldfarb, Ed Mosher and Ray Lorie
SGML was thought of as being too complex for the general population, and HTML was created to present the data
XML was created to complete the gap between SGML and HTML
SGML is a language used to specify mark-up languages, its name makes is easy to believe that it is a markup language in its own right
SGML was intended for documents that are published on the INTERNET, but it was too complicated, and something, which was simpler was need
Therefore, XML, was developed to replace, all the complicated systems that were being used, to transmit data over the INTERNET
<strong>XML is a simplified form of SGML or any other system used, to transmit data over the INTERNET</strong>
SGML was mainly created to develop vocabularies, which can markup documents with structural tags
The development of XML, in the 1990s started because of the complexities of SGML
XML is easier to use, and help web masters and developers do their jobs, much better
Before XML was around, computers, were thought to have to be, very complicated and complex for them to work properly
At the time some people thought that machine that read documents should remain in that state for many years
However, as the new generation came on the scene, we have seen how technology, computers and the programming world has changed, through the years
XML Architecture:
Logical and physical structures, are each part of an XML document, XML documents with a logical and a physical structure are physically composed of units, also known as entities
In order to include an entity in an XML document, an entity will refer to it
The beginning of a document is its document entity or its root
These same XML documents composed of a physical and a logical structure are logically composed of elements, comments, declarations, processing instructions and character references
Explicit markup indicate all logical components
The architecture of an XML document can also be defined, in Data Type Definition (DTD) documents and the XML schema documents
The legal building blocks of an XML document are defined by a DTD document
DTD documents provide a list of legal elements and attributes, which define an XML document structure
An XML document may have an external reference of a DTD, or they can include the declaration of the DTD inside the XML document
An XML schema is used to replace a DTD, they describe the structural components of an XML document
XML documents also have XML schema, which is a language, which is also known as XML Schema Definition (XSD)
XML documents have constraint rules applied to it; these rules are specified in both DTD and XML documents
The architecture of an XML document is a hierarchical tree structure, which is composed of a single root elements, which contains sub-elements, those sub-elements contain their sub-elements and so on
XML elements are composed of other elements, data, a combination of both or/and empty element
XML Syntax
The data structure of an XML document is defined by the author, because XML does not have restrictions on the element names; the only restrictions that XML imposes, is the way the name is structured, meaning that certain characters, can’t be used to form an XML element name
Nevertheless, the language author decided what names, are appropriate for the particular data structure
The text that XML documents use to communicate and carry information to servers, has to be described and identified
Element names help allow XML, to describe the data, regarding of their structural and semantic role
A simple XML document would look similar to the following lines of code
<?xml version=”1.0 encoding=”UTF-8″?> The first line of this XML document simply specifies the XML version, which the author is using, it is only recommended that an XML document, begins with such XML declaration
Some browsers may have difficulties reading your document, if such document does not define, the version that is being used, in the XML document
In this case the XML version being used in 1.0, this is the most used version and is the currently approved version; however others may appear in the near future
Especially by the time, you read this article, I am sure another version is in the works, right now
You know how I know, well I am part of technology, and I know how fast technology, has to move, in order to stay relevant
Technology has to be upgraded, this is why I am sure that another version of XML, which is better, is being developed right now
The first line also contains the UTF-8 (UCS Transformation Format—8-bit); all XML parsers are required to support, the Unicode “UTF-8” and “UTF-16” encoding
UTF-8 is unlike UTF-16 as it avoids the complications, of endianness and byte order mark
Therefore UTF-8 is the Unicode character encoding, which is most used today in XML documents
Many other XML parsers, also support other encoding as well, such encoding is “ISO-8859-1”
The XML declaration has other rules that the document’s author must follow
If the author of the document does not create the document following these rules, some browsers may not be able to read the XML document
Such rules are the fact that the XML declaration, is case sensitive
The word XML cannot be the upper case, and the document must always begin with this <?xml, which is considered to be valid Whitespace and or comments. Any character may not appear before the declaration if the declaration is used.
The second line on the XML document sample above, indicates the place where the elements and data originates In the sample above the elements and data originated from http://www.w3.org/2001/XMLSchema
The subsequent lines represent the elements of the documents, elements are the building blocks of markup languages, including XML Any needed elements can be created in XML, however, these elements must be described in an internal, or external schema, or Document Type Definition (DTD)
The XML elements, are the information unit within XML documents;
This information consist of a start tag and an end tag XML tags begin with the less-than character (“<”) and end with the greater-than character (“>”) Tags help elements become the logical units of information in an XML document, an element may consist of a start tag, followed by text and finally the end tag An end tag includes a solidus (“/”) before the element’s name
This is an example of an XML file that contains elements and tags:
<?xml version=”1.0″?> Jane Smith AT&T (212) 555-4567
XML Covers the Loose Ends in the Online World
The main reason why XML was created, was because Hypertext Mark-up Language (HTML) and Standard Generalized Markup Language (SGML) had limitations, which made the mark up languages weak without the use of XML
The World Wide Web Consortium (W3C) recommended XML, to be the standard technology used, to transmit data over the INTERNET
In other words W3C, recommended developers to treat XML as a standard, the W3C standards are widely accepted and implemented today
XML has a lot of similarities with SGML, because XML is a subset of SGML, XML is used to streamline SGML and focus on the main and most important uses of SGML, which would support the INTERENT
One of the uses where XML has proved to be very important, is in the use of Asynchronous JavaScript and XML (AJAX)
AJAX is a combination of Dynamic HTML, and XML using XMLHttpRequest object in JavaScript
DHTML is a combination of JavaScript, CSS, and DOM and is widely-implemented in websites today
The XMLHTTPREQUEST is an object that enables, the transmission of data to and from the web server; this data is usually in XML format
The online world is covered by many computer languages working together, XML is one of them
XML make it easier to transport data, from and to a web server
This action enables developers to create website applications, to be more efficiently, because XML reduces the amount of space that data may take to be transported
XML is widely used, but don’t forget that just like XML did SGML, there are already other technologies and resources, which can do what XML does, more efficiently
Thank you for reading this article!!!
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