XML Document Structure, Introduction to Web Services

XML(Extensible Markup Language) 

XML is an extensible markup language used for the description and delivery of marked-up electronic text over the Web. Two important characteristics of XML distinguish it from other markup languages: its document type concept and its portability. An important aspect of XML is its notion of a document type. XML documents are regarded as having types. XML’s constituent parts and their structure formally define the type of a document. Another basic design feature of XML is to ensure that documents are portable between different computing environments. All XML documents, whatever language or writing system they employ, use the same underlying character encoding scheme. This encoding is defined by the international standard Unicode, which is a standard encoding system that supports characters of diverse natural languages. An XML document is composed of named containers and their contained data values. Typically, these containers are represented as declarations, elements, and attributes. A declaration declares the version of XML used to define the document. The technical term used in XML for a textual unit, viewed as a structural component, is element. Element containers may be defined to hold data, other elements, both data and other elements, or nothing at all. An XML document is also known as an instance or XML document instance. This signifies the fact that an XML document instance represents one possible set of data for a particular markup language. The example in Listing 3.1 typifies an XML document instance. This example shows billing information associated with a purchase order issued by plastics manufacturer. We assume that this company has built a business based on providing “specialty” and custom-fabricated plastics components on a spot and contract basis.

Example of an XML document instance

<?xml version="1.0" encoding="UTF-8"?>

 <BillingInformation> 

<Name> Right Plastic Products </Name> 

<BillingDate> 2002-09-15 </BillingDate> 

<Address> 

<Street> 158 Edward st. </Street> 

<City> Brisbane </City>

 <State> QLD </State>

 <PostalCode> 4000 </PostalCode>

 </Address>

 </BillingInformation>