XML Attributes

From HTML you will remember this: < IMG SRC="comp.gif" >. The SRC attribute provides additional information about the IMG element. In HTML (and in XML) attributes provide additional information about elements:

< img src="computer.gif" >
< a href="demo.asp" >

Attributes often provide information that is not a part of the data. In the example below, the file type is irrelevant to the data, but important to the software that wants to manipulate the element:

< file type="gif" > computer.gif < /file >
Students now u know abt basic XML, its scripting rules. Lets understand XML attributes which can be understood as property of an element.

Here are simple rules for XML elements

Quote Styles, "female" or 'female'?
Attribute values must always be enclosed in quotes, but either single or double quotes can be used. For a person's sex, the person tag can be written like this:

< person sex="female" > or like this:
< person sex='female' >

Note: If the attribute value itself contains double quotes it is necessary to use single quotes, like in this example:

< Inspector name='George "Rain" Abslum' >

Note: If the attribute value itself contains single quotes it is necessary to use double quotes, like in this example:

< Inspector name="George 'Rain' Abslum" >

Use of Elements vs. Attributes: Data can be stored in child elements or in attributes.

E.g. Take a look at these examples:

< firstname > Anna < /firstname >
lastname > Smith < /lastname >
< /person >
< person >
< sex > female < /sex >
< firstname > Anna > /firstname >
< lastname > Smith > /lastname >
< /person >

In the first example sex is an attribute. In the last, sex is a child element. Both examples provide the same information. There are no rules about when to use attributes, and when to use child elements. My experience is that attributes are handy in HTML, but in XML you should try to avoid them. Use child elements if the information feels like data.

E.g.Storing data in child elements.

The following three XML documents contain exactly the same information:
A date attribute is used in the first example:
< note date="12/11/2002" >
< to > Tove < /to >
< from>Jani < /from >
< heading>Reminder < /heading >
< body>Don't forget me this weekend! < /body >
< /note >

A date element is used in the second example:

< note >
< date > 12/11/2002 < /date >
< to > Tove < /to >
< from>JaniReminder < /heading >
< body>Don't forget me this weekend! < /body >
< /note >
An expanded date element is used in the third: (THIS IS MY FAVORITE):

< note >
< date >
< day > 12 < /day >
< month > 11 < /month >
< year > 2002 </year >
< /date >
< to > Tove < /to >
< from > Jani < /from >
< heading > Reminder < /heading >
< body >Don't forget me this weekend! < /body >
< /note >

Element naming

XML elements must follow these naming rules:

• Names can contain letters, numbers, and other characters
• Names must not start with a number or punctuation character
• Names must not start with the letters xml (or XML, or Xml, etc)
• Names cannot contain spaces

Take care when you "invent" element names and follow these simple rules:
Any name can be used, no words are reserved, but the idea is to make names descriptive. Names with an underscore separator are nice.

Examples: < stud_name >, < stud_age > .


Avoid "-" and "." in names. For example, if you name something "first-name," it could be a mess if your software tries to subtract name from first. Or if you name something "first.name," your software may think that "name" is a property of the object "first." Element names can be as long as you like, but don't exaggerate. Names should be short and simple, like this:



< Thesis_title > not like this: < the_title_of_the_book >.



XML documents often have a corresponding database, in which fields exist corresponding to elements in the XML document. A good practice is to use the naming rules of your database for the elements in the XML documents. Non-English letters like éòá are perfectly legal in XML element names, but watch out for problems if your software vendor doesn't support them. The ":" should not be used in element names because it is reserved to be used for something called namespaces (more later).