XML middleware or XML mapping is much like object-relational mapping. It usually involves mapping between XML and relational data, but can also include mapping between XML and object data.
Since XML is inherently important to XML middleware, be sure to look at the articles on XML.
Finally, in addition to the articles listed below, be sure to check out the database concepts and standards articles. Many of these database concepts apply to all forms of database management systems: relational (RDBMS), object (ODBMS), XML (XDBMS), and others as well as object-relational mapping and XML middleware or XML mapping products.
The Savvy Manager's Guide
Douglas K Barry is also the author of a book that explains Web Services, service-oriented architecture, and Cloud Computing in an easy-to-understand, non-technical manner.
Web Services, Service-Oriented Architectures, and Cloud Computing: The Savvy Manager's Guide (Second Edition)
by Douglas K Barry with David Dick
This is a guide for the savvy manager who wants to capitalize on the wave of change that is occurring with Web Services, service-oriented architecture, and—more recently—Cloud Computing. The changes wrought by these technologies will require both a basic grasp of the technologies and an effective way to deal with how these changes will affect the people who build and use the systems in our organizations. This book covers both issues. Managers at all levels of all organizations must be aware of both the changes that we are now seeing and ways to deal with issues created by those changes.