Validating xml parser requires
The reason is that XML software should be small, fast, and compatible.
The constructors using more than a single argument are only relevant if you want to validate against a DTD and need to provide the location of the DTD itself - for details see the next section.This ends up as a kind of family-tree structure in the application's memory (tree structures are a common way for programs to store related data).As well as built-in parsers, there are also stand-alone parser-validators (see Bill Rayer’s tip), which read an XML file and tell you if they find an error (like missing angle-brackets or quotes, or misplaced markup).A parser looks at your code and highlights lines that may cause problems.
XML parsers are available in two flavors, non-validating and validating.
It is important to know the difference between these two styles before selecting a parser.