Called at the point each Element starts validation.

[C#]
virtual bool Start(Element element)
virtual void Start(string entry)
virtual void Start(int index)

[Visual Basic]
Overridable Function Start(element As Element) As Boolean
Overridable Function Start(entry As string) As void
Overridable Function Start(index As int) As void


Called at the point each Element starts validation.

If the Element has already been seen then this function should return false to indicate that it has already been validated.

If not then the function should return true to indicate that validation should go ahead.

Subclasses should keep track of elements that they have seen so as to avoid recursive loops.