AElfred2 and SAX2 Utilities

gnu.xml.aelfred2	This package contains Ælfred2, which includes an enhanced SAX2-compatible version of the Ælfred non-validating XML parser, a modular (and hence optional) DTD validating parser, and modular (and hence optional) JAXP glue to those.
gnu.xml.pipeline	This package exposes a kind of XML processing pipeline, based on sending SAX events, which can be used as components of application architectures.
gnu.xml.util	This package contains XML utilities, including SAX2 XML writers and a parser of DOM trees, plus a command line driver.

DOM2, implementing DOM Level 2

gnu.xml.dom

This is a Free Software DOM Level 2 implementation, supporting these features: "XML", "Events", "MutationEvents", "HTMLEvents" (won't generate them though), "UIEvents" (also won't generate them), "USER-Events" (a conformant extension), and "Traversal" (optional; no TreeWalker yet).

SAX and SAX2

org.xml.sax	This package provides the core SAX1 and SAX2 APIs.
org.xml.sax.ext	This package contains interfaces to optional SAX2 handlers, providing parts of SAX2 which (like the standard feature flags and unlike namespaces) can't be layered over SAX1.
org.xml.sax.helpers	This package contains "helper" classes that are used to bootstrap SAX-based applications.

DOM Level 2 (W3C)

org.w3c.dom

Contains the core and "XML" feature set of the DOM Level 2 Recommendation.

Java API for XML (v1.1) (Sun)

javax.xml.parsers