| Immutable in-memory representation of grammar.
This object represents a set of constraints that can be checked/
enforced against an XML document.
A {@link Schema} object is thread safe and applications are
encouraged to share it across many parsers in many threads.
A {@link Schema} object is immutable in the sense that it shouldn't
change the set of constraints once it is created. In other words,
if an application validates the same document twice against the same
{@link Schema}, it must always produce the same result.
A {@link Schema} object is usually created from {@link SchemaFactory}.
Two kinds of validators can be created from a {@link Schema} object.
One is {@link Validator}, which provides highly-level validation
operations that cover typical use cases. The other is
{@link ValidatorHandler}, which works on top of SAX for better
modularity.
This specification does not refine
the {@link java.lang.Object#equals(java.lang.Object)} method.
In other words, if you parse the same schema twice, you may
still get !schemaA.equals(schemaB). | 