XML Elements

Elements

Elements are used to categorize the data in XML document, thus making the data “self-explanatory”. A tag is just another name for an element.  An opening tag is the element name enclosed in brackets and a closing tag is the same as an opening tag with a slash before the element name.  The information of the elements is enclosed within open and closing tags. An example of this is shown below:

 

Example: <animal>cat</animal>

 

Attributes are used provide more specific information about the element and appear within the opening tag.  Attributes provide a way to focus elements in a way to fit the needs of the XML document creator. If there are several values possible for an attribute, the value must be specified.  So if a tag has an attribute for color the values may be green, yellow, blue, red, etc.  An example of an element attribute is the following:

Example: <animal breed=Siamese>cat</animal>

There are some rules to consider when determining element names.  They are the following:

  • cannot contain spaces
  • can contain letters, numbers, and any other characters
  • cannot begin with a number or a punctuation character
  • cannot begin with “xml”

With these rules in mind, there are also some best practices associated with element naming.  They include the following:

 

  • Since some XML documents have a corresponding database it is a good idea to use the naming rules of that database.
  • Non-English letters are acceptable in XML, but be sure that the software being used supports them.
  • Make names as descriptive as possible.
  • Don’t hesitate to use an underscore as a separator: <first_letter>, <last_letter>.
  • Try to keep names short and simple.  For example, Use <baby_name> rather than <the_name_of_the_baby>.
  • Avoid the “.” character. For example, in “first.letter,” some software may interpret this to mean that “letter” is a property of the object “first.”
  • Avoid the “-” character. For example, in “first-letter,” some software may interpret this to mean that you want to subtract “letter” from “first”.
  • Avoid the “:” character because colons are usually reserved for namespaces.
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