This gives the function an opportunity to report all the errors and raise an exception rather than doing this when it sees th first one.This function can do what it likes with the information.When an XML tag (element) is processed, we look for a function in this collection with the same name as the tag's name. All but the last should take the XMLnode as their first argument.In the future, other information may be passed via …, for example, the depth in the tree, etc.
This applies to regular nodes and also comments, processing instructions, CDATA nodes, etc.
They do become an issue when dealing with a node's chidren directly and so one can use simple filtering techniques such as # tags.
We discard all other tags by returning NULL # from the start Element handler.
This causes validation and processing of a DTD to be turned off.
This is currently experimental so that we can implement a logical value for use when we have handler functions and are traversing the tree.