Elements can contain textual data. Elements can contain only other specified elements and no text. The contained element are called children of the containing element. The containing element is the parent of the child elements. Element can contain a mix of textual data and other specific elements.
Empty elements get their value from their attributes.
An empty element will typically have at least one attribute. In HTML, the IMG tag is a good example of an empty element. It gets its value from the src attribute. Number of Occurences You can specify the number of times a child element is used within its parent. Once and only once.