We'll introduce wireless programming languages by first discussing the three markup languages. These include Hypertext Markup Language (HTML), Extensible Markup Language (XML), and the combination of the two, Extensible Hypertext Markup Language, (XHTML).
HTML is the primary format used on the World Wide Web. HTML can display Web pages with a wide range of colors, shapes , and objects. Although not a true programming language, HTML has increased in power over the years .
HTML is actually a loosely defined subset of XML. However, whereas XML is a strict language (as you will learn), HTML takes many liberties that have helped it become the popular presentation tool it is today. Although the spirit of the young Internet encouraged freedom, developers have now realized that the freedom of HTML has repercussions . Because HTML is so flexible, many browsers and Web applications have added their own functionality to the base HTML protocol. Like all enhanced functionality, this comes with additional security risks.
For this reason, efforts are underway to replace HTML with a much more regulated and standardized markup language known as XHTML.
XML is the foundation for many data formats, including HTML, WML, XHTML, and more. It has recently become popular because it can facilitate the transfer of data between widely disparate programs, operating systems, and companies. The key to XML's utility is that it enables any developer to design her own data format using her own terms and requirements. In fact, XML is so popular that Microsoft has built its entire suite of products, from operating systems to server components , around the concept of XML.
To illustrate the utility of XML, let's consider a sample corporation that needs to share information about fruit inventory. Because direct access to a database would be a security risk (as well as poor business practice), the developer can create an XML program that defines the type, size, and color of each fruit on hand. Once she has determined the specs , the developer could program the host with the capability to pull data from a database and convert it to an XML file. On the other end, a special client could scan the generated XML file and parse the information to fill its own database. This process would thus allow for rapid and standardized data transfer.
To illustrate this, consider the following sample source code to see how such an XML file would appear. Note the hierarchy and the matching set of labels. Each label is a property, which could have sub-properties. In this case, we are passing information about an apple and a grape.
<FRUIT> <NAME>APPLE <COLOR>RED</COLOR> <SIZE>BIG</SIZE> </NAME> <NAME>GRAPE <COLOR>PURPLE</COLOR> <SIZE>SMALL</SIZE> </NAME> </FRUIT>
By extrapolating from this simple example, you can see how XML data is organized. The use of such relational data methods is still in its infancy, and will continue to grow for many years.
Although XML is the foundation of many other Internet-based formatting languages, its subsets are giving XML the push it needs to become the de facto standard. A recent subset, XHTML, is slowly gaining ground, and is destined to overtake HTML in prevalence.
Thus, XHTML will likely replace HTML. Although this process will take several years, many Webmasters have already embraced XHTML, and are slowly integrating its rules into their development. In fact, XHTML 1.0 is considered by many to be the next version of HTML (HTML 5.0).
What makes XHTML so popular is its simple yet rigid ruleset. This ruleset is so powerful because it enforces a universal standard. The rules are as follows :
By contrasting these simple but powerful rules with HTML, you can begin to see the advantages of XHTML. In addition, PCS (Personal Communication Service) devices also use XHTML. Because of the myriad of vendors , each with its own proprietary approach, the strict rules of XHTML and XML are vital . Without this standard, Web developers would have to create separate Web pages for each device. Fortunately, because of this standard, developers can create one or two pages for all devices. However, XHTML is still too bloated for many smaller PCS devices. Therefore, another option is required.