Web Site Development and Information Architecture - Coursework Example

XML (Extensible Markup Language) (An In-Depth Analysis) Web Site Development and Information Architecture Faculty Date Table of Contents I.Introduction 3 II.The background and history 4 III.XML Overview 6 IV.A comparison between XML and HTML 11 V.XML Uses in Todays Web Environment 12 VI.Behind-the-Scene Uses of XML 14 References: 15 I. Introduction XML stands for Extensible Markup Language which is designed to describe data and to focus on what data is (XML Tutorial1). It is a Meta language that allows user to create and format their document markups. XML is a document-processing standard that is an official recommendation of the World Wide Web Consortium (W3C), the same group responsible for overseeing the HTML standard (Eckstein & Casabianca, 2001). According to Eckstein & Casabianca (2001), XML is actually a simplified form of Standard Generalized Markup Language (SGML2), which is extremely complex, especially for the Web. The main credit for XML creation is attributed to Jon Bosak of Sun Microsystems, Inc., who started the W3C working group responsible for scaling down SGML to a form more suitable for the Internet. This paper will cover an in-depth analysis of Extensible Markup Language (XML). Initially, it will provide a brief background and history (evolution) of XML. In the next section, the paper will present an overview of XML. After that a comparison between XML and HTML will be presented. This paper will also discuss how XML is used in today’s web environment and what behind-the-scene uses of XML are. II. The background and history XML is a descendant of SGML, the Standard Generalized Markup Language. SGML was invented by Charles F. Goldfarb, Ed Mosher, and Ray Lorie at IBM in the 1970s and developed by several hundred people around the world until its eventual adoption as ISO standard 8879 in 1986. SGML is extremely powerful and complex and achieved some success in domains that needed ways of efficiently managing technical documents that were tens of thousands of pages long, especially in U.S. military and government, in the aerospace sector. However, SGML is so complex that almost no software has ever implemented it fully. HTML is an SGML application and is considered as biggest success of SGML. (Harold & Means, 2002) According to Harold & Means (2002), In 1996, Jon Bosak, Tim Bray, C. M. Sperberg-McQueen, James Clark, and several others began work on a "lite" version of SGML that retained most of SGMLs power while trimming a lot of the features that had proven redundant, too complicated to implement, confusing to end users, or simply not useful over the previous 20 years of experience with SGML. This resulted in development of XML 1.0, in February 10, 1998 and became an immediate success as it was taken whole-heartedly by people across the world from domains ranging from legal court filings to hog farming. After that, the next standard was out as Namespaces in XML, which was an effort to allow markup from different XML applications to be used in the same document without conflicting. The next step was the Extensible Stylesheet Language (XSL), which is an XML application for transforming XML documents into a form that could be viewed in web browsers. XSL was further divided into XSL Transformations (XSLT3) and XSL Formatting Objects (XSL-FO4). The current version is Extensible Markup Language (XML) 1.0 (Fourth Edition), recommended on 16 August 2006 and edited in place 29 September 2006 by World Wide Web Consortium (W3C5) (The World Wide Web Consortium (W3C)6). III. XML Overview XML is a markup language and was designed to describe data by using a Document Type Definition (DTD) or an XML Schema. XML tags are not predefined as like HTML. XML is a W3C Recommendation (XML Tutorial).The basic terminology of XML document is: text ………. Any XML element consists of two tags: an opening tag “” and a closing tag “”. Elements can have attributes applied that are often used to further refine or modify the default meaning of an element, such as the following: 25.43 There is also empty elements support in XML that has no text between the opening and closing tags and are combined (optionally) by placing a forward slash before the closing marker. Below shown elements are same: In general, two files are needed by an XML-compliant application to use XML content are the XML document and Document Type Definition (DTD). Additionally, another type of file is commonly used to help display XML data: the stylesheet. The stylesheet dictates how document elements should be formatted when they are displayed. (Eckstein & Casabianca, 2001) A XML Document contains the document data, typically tagged with meaningful XML elements, any of which may contain attributes. A Simple XML Document is given below: XML Pocket Reference 12.95 The code between the in the first line is called as an XML declaration. The second line points out the ‘root element’7 of the document, as well as the DTD validating each of the document elements that appear inside the root element. Here, the element serves as the root element of the document and the SYSTEM keyword denotes that the DTD of the document resides in an external file named sample.dtd. The line is comment. Namespaces: Namespaces were created to ensure uniqueness among XML elements and are not mandatory in XML. The elements , , and are XML elements. In element tag, the portion before the colon (:) identifies the tags namespace; the portion after the colon identifies the name of the tag itself. Namespaces help to avoid element collisions by scoping each tag. Namespaces are useful in the case where there is need of combining two documents of same type. The elements of the two documents combined can be easily identified by their namespaces. Otherwise, if two XML documents containing identical elements from different sources are merged, those elements are said to collide. Document Type Definitions (DTD): A DTD specifies how elements inside an XML document should relate to each other and provides grammar rules for the document and each of its elements. A document adhering to the XML specifications and the rules outlined by its DTD is considered to be valid. (Eckstein & Casabianca, 2001) The Root Element: Every XML document has one element that does not have a parent and it is the first element in the document that contains all other elements. For below example the is root element. Figure 1 shows the tree diagram for the below example of an XML. Alan Turing computer scientist mathematician cryptographer Figure 1: A tree diagram [1] The Life of an XML Document: Figure 2 shows the life of an XML document. Initially, an XML document is created in an editor. After that, the XML parser reads the document and converts it into a tree of elements and passes the tree to the browser or other application that displays it. (Harold, 2004) Figure 2: The Life of an XML Document (Harold, 2004) According to Eckstein & Casabianca (2001), there are basic rules for a well-formed document: XML is case-sensitive, this means that and are not the same. All element attribute values must be in single or double quotation marks. An element must have both an opening and a closing tag, unless it is an empty element. If a tag is a standalone empty element, it must contain a closing slash (/) before the end of the tag. All opening and closing element tags must nest correctly. This is incorrect incorrect This is correct correct Isolated markup characters are not allowed in text; < or & must use entity references. In addition, the sequence ]]> must be expressed as ]]> when used as regular text. Well-formed XML documents without a corresponding DTD must have all attributes of type CDATA by default. IV. A comparison between XML and HTML In an HTML, an existing markup is static: and , and are tightly integrated into the HTML standard and can not be changed or extended. However, XML allows creating user own markup tags and allows to configure each tag what user like. Each of the elements (tags) can be further defined by document type definitions (DTD) and stylesheets and applied to one or more XML documents. Therefore, it might be case that for future web development, XML can be used to describe data, while HTML can be used for formatting and displaying the data (Eckstein & Casabianca, 2001) (XML Tutorial). Two main difference between and XML and HTML are described in below paragraphs. XML was designed to carry data: XML was designed to describe data and to focus on what data is. However, HTML was designed to display data and to focus on how data looks. XML is a Complement to HTML and can not be used as replacement for HTML as both XML and HTML were designed with different goals. HTML is about displaying information, while XML is about describing information. (XML Tutorial) XML can separate data from HTML: XML makes it possible to store data outside HTML. In HTML, for displaying data it is stored in it. XML can be used to store that data outside HTML in an XML file. By this way user can concentrate on using HTML for data layout and display and changes in data can be done in XML file only. However one can store XML data inside HTML page too and can concentrate on using HTML only for formatting and displaying the data. V. XML Uses in Todays Web Environment Almost all the web development technologies such as JSP, J2EE, Java, .NET, ASP, and PHP use XML in some form. XML can be used for creating new languages, for example: the Wireless Markup Language (WML), used to markup Internet applications for handheld devices like mobile phones, is written in XML. There may be possibility that in future all the application may be written so that they can exchange data in XML format to one-another. Some of the common uses of XML are: XML in Web Development: The XHTML web pages are a stricter and cleaner version of HTML. XHTML is almost identical to HTML 4.01. XHTML is a combination of HTML and XML. XHTML consists of all the elements in HTML 4.01 combined with the syntax of XML. The main benefits that XML provides is that XML can create Web documents using XSLT to transform documents using an XSLT processor into HTML. This enables users to make available their documents in whatever format they want. XML and Content Management: XML is used for developing content management applications. However, most of the front-end users of Content Management System (CMS) never know this. This is because the CMS sits in front of XML to make it easier for the content writers to write their web content. Therefore, they do need to worry about how to write HTML or design web pages. XML and Documentation: XML is used by many companies to write their internal documentation. The most common platform used for this is DocBook. For documentation, the XML gives advantages in terms of defining the common traits in books, magazines, stories, advertisements, and so forth and all these types are defined in DocBook. The main advantage that XML gives for documentation is that XML is easy to understand and can be used for any type of documentation, from a publishing house to Marketing materials. XML and Database Development: XML is used most frequently for databases. XML for databases does not need to be inherently human readable. The data is simply written in such a way to allow machines to read it and make it accessible to a database. (Kyrnin, n.d. ) To Exchange Data between Incompatible Systems: With the use of XML data can be exchanged between incompatible systems. In real world, it is the most time-consuming challenges for developers to exchange data between computer systems and databases that contain data in incompatible formats. However, by converting the data to XML format this complexity can be solved and the data can be used and read by different types of applications. (XML Tutorial) VI. Behind-the-Scene Uses of XML According to Harold (2004), many software vendors are moving to XML for their own data simply because it is a well-understood, general-purpose format for structured data that can be manipulated with easily available, cheap, and free tools. Some of them are: Microsoft Office 2003: Office 2003 is the first edition to move away from the traditional undocumented proprietary, closed, binary formats of the past and move forward into the open world of XML. Most of the Office 203 applications such as Word, PowerPoint, Excel, and Visio enables user to save their documents in XML format. However, binary format is still used as default. It gives many advantages such as XML makes possible office files to exchange with other programs (Harold, 2004). Netscape Relation with XML: Netscape 6.0 and later support direct display of XML in the browser. Netscape actually started using XML internally as early as from version 4.0.6 (Harold, 2004). United Parcel Services (UPS): UPS makes a number of tools available to their customers to track shipments over the Internet8, check shipping rates, validate addresses, and more. They sent content from UPS server to the customer who requests it so that online stores and other shippers could paste it into their web Pages. Initially, they were using HTML code that did not easily mesh neatly with the site’s code and look out of place. Then they started offering the same information in XML that can be easily manipulated using an XSL style sheet or other tool to take on the form the site needs, giving a much more flexible solution (Harold, 2004). References: Eckstein, R. & Casabianca, M. (2001). XML Pocket Reference (2nd Ed.). United States of America: OReilly & Associates, Inc. Harold, E. R. (2004). XML 1.1 Bible, (3rd Ed.) United States of America: Wiley Publishing, Inc. Harold, E. R. & Means, W. S.  (2002). XML in a Nutshell (2nd Ed.). United States of America: OReilly & Associates, Inc. Hansen, E. & Festa, P (2003) Developers reflect on the Webs lingua franca. CNET News.com, February 10, 2003. Retrieved November 28, 2007, from http://www.news.com/2009-1001-983871.html Kyrnin, J. Who Uses XML? Your Guide to Web Design / HTML Retrieved November 28, 2007, from http://webdesign.about.com/od/xml/a/aa060401a.htm The World Wide Web Consortium (W3C). Viewed on 28, 2007, available at http://www.w3.org/ XML Tutorial. Retrieved November 28, 2007, from http://www.w3schools.com/xml/default.asp Read More