104 Chapter 5. Conformance · Validating and Non-Validating Processors · Using XML Processors This chapter lays down the law about what constitutes a legal, working XML processor. In particular, it spells out the different requirements for validating and non-validating processors. Because the specification's distinction between well-formed and valid documents may cause confusion, this sec- tion spells out their relationship. Validating and Non-Validating Processors Conforming XML processors fall into two classes: validating and non-validating. Validating and non-validating processors alike must report violations of this specification's well-formedness constraints in the content of the document entity and any other parsed entities that they read.