OpenTop is a cross-platform, high-performance C++ class library that extends the standard C++ library to provide features similar to (and modelled on) core Java facilities such as resource management, networking, I/O, multi-threading and support for the full Unicode character range. OpenTop also contains a supplementary C++ XML Toolkit which features a SAX-based validating XML parser.
Babeldoc is a framework and set of applications to process documents for business-to-business and other Internet/integration applications. It is primarily intended for text documents, especially XML, but supports a wide range of operations and data types. It has a sophisticated journaling system that supports replaying and reprocessing. Babeldoc is pipeline based and supports numerous ways to combine the pipeline stages in a dynamically reconfigurable fashion. It has a GUI and a Web-based console for document processing and monitoring, and comes with tools for the tranformation of flatfile data to XML, archival, and cryptography. Additionally it is able to scan various data sources based on sophisticated constraints.
XED is a text editor for XML document instances. It is designed to support hand-authoring of small-to-medium-sized XML documents, and is optimized for keyboard input. It works very hard to ensure that you cannot produce a badly-formed document. Although it does not validate, the results of offline validation can be accessed, and it does read DTDs and keep track of your document structure, and provides context-based accelerators to make element and attribute entry fast and easy.
oXygen is an XML editor that supports any XML document, and works with XML Schemas, DTDs, Relax NG schemas, and NRL Schemas. It has powerful transformation support that allows you to edit XSLT and XSL-FO documents and to obtain documents in the desired output format (such as HTML, PS, or PDF) with just one click. It also includes a complete Subversion client, support for flattening XML Schemata, an XML Schema instance generator, integration with the X-Hive/DB, MarkLogic and TigerLogic XML databases, editing actions on the diagram, and a rename refactoring action.