eXtensible Markup Language (XML)
- XML is developed by the World Wide Web Consortium (W3C), which is used as a format to store and transfer data over the Web.
- XML is a markup language based on simple, platform-independent rules for processing and displaying textual information in a structured way.
- XML was designed to carry data, not to display data.
- An XML document can be converted into another format, such as HTML and PDF, to make it more readable.
- XML has been used to implement the following various operations, like
- Configuration information
- Electronic Data Interchange (EDI)
- Voicemail system
- Remote Method Invocation (RMI)
- Object Serialization
Differences and similarities from HTML
Similarities between XML and HTML
- Both are originated from SGML. [Standard Generalized Markup Language]
- Tags are basic building blocks of both HTML and XML documents.
- Both are markup languages of web.
- Both XML and HTML markups are used for responses either Direct or by AJAX.
- Both HTML and XML are used to carry information. HTML is the standard markup for the web for displaying and formatting the data whereas XML is used for data binding / handling.
Difference between XML and HTML
- HTML focuses on how data looks whereas XML focuses on what data is.
- HTML tags are predefined tags whereas XML tags are user defined tags.
- HTML tags are not case insensitive whereas XML tags are sensitive.
- In HTML not mandatory to close tag whereas in XML it is mandatory to close tag.
- HTML is presentation language whereas XML is neither programming nor presentational language.
Entities & Attributes in XML
Entities in XML
- Some characters have a special meaning in XML. For example, the less than sign
(<) marks the beginning of a tag. And, of course, the greater than sign
(>) marks the end of the tag.
- When the XML processor parses the document, it looks for these characters to determine how to interpret the document.
- Imagine you had the following text within an element:
10 < 5. When the XML processor encounters the
<, it will assume it's the start of an opening tag.
- In order to include characters such as
& etc. you need to use their entity reference instead of the character itself.
- Entity Syntax - Entity reference using the
& character and close it using the
Attributes in XML
- Attributes give the information about the elements. They can be specified only in the element start tag and their values are enclosed in either single or double quotes
<tag attribute = “value” >description </tag>
- XML attributes cannot contain multiple values, tree structures and also attributes are not easily expandable (for future changes).
- Attribute values are difficult to test against the DTD and also difficult to maintain programmatically.