W3C's XML-Related Specs and Tutorials
XML Technology Standards (XML, XSL, XSD, XPath, XProc, etc.)
w3schools XML Tutorials Home
Saxon XSLT Processor
Schema Supplementation (e.g. business-rules validation)
oXygen XML Editor (and related software)
XML Pipeline (XProc) Engines
PDF Engines
RenderX (a.k.a. XEP)
Antenna House Formatter (a.k.a. AHF)
Apache FOP
XML to Java Data Binding
Java Architecture for XML Binding (JAXB) , V2, at Github
XMLBeans
DITA (Darwin Information Typing Architecture)
DITA 1.0 - 1.3 Specs at OASIS (Technical Work Produced by the Committee)
DITA Open Toolkit
DITA Demonstration Collection
DocBook
DocBook 5.2 : The Definitive Guide
DocBook XSL: The Complete Guide (4th Ed.)
DocBook Schemas at OASIS
DocBook Wiki Home
Native XML Databases (Open-Source)
XSLT and XQuery Unit Testing
Web Security and XML
An In-Depth Look At XML Document Attack Vectors
XML Risks and Mitigations by The MITRE Corporation
XML External Entity (XXE) Injection Attacks
XML XXE Prevention at The OWASP (Open Web Application Security Project) Foundation
OWASP XML Security Cheat Sheet
Binary XML (a.k.a. "EXI")
Binary XML on Wikipedia
Efficient Extensible Interchange Working Group at W3C
Generation of Synthetic XML Documents
IMS Question and Test Interoperability (QTI) Resources
Explore QTI in depth
QTI 2.1 Tool Tutorial
Uniqurate
ONYX Editor (assessment authoring tool)
QTIWorks
QTI Specs at IMS Global Learning Consortium
The Latest XML News
XML.com
Other Resources
XML Press : XML for Technical Communicators