When Good Servers Meet Bad Clients

Coherity XML Database (CXD) 3.0

by Kurt Cagle

New Architect
October 2002

The problem with XML is that it is only structured if you're extremely careful in laying out schema. Structured databases such as Oracle 9i and Microsoft SQL Server can handle certain types of XML data translations cleanly. However, if your initial data is even slightly semi-structured (as with almost any XHTML Web page, for example), then you'll need to write some serious gyrations in table design, truly warped stored procedures, and dodgy SQL statements in little boxes.

Pure XML databases solve these translation nightmares. Most work on a similar premise: You add XML content to the database, where it is broken down into a linear data store with the connections indexed for retrieving the content efficiently. In some cases, the connections are made relevant to existing "folder" content as a hierarchical super-tree of XML content; in other cases the connections between documents are much less explicit.

Such databases differ from their SQL relational counterparts in that they emerged after both the Web and XML became dominant factors in the evolution of data access. For that reason, XML databases are designed to work within an existing Web architecture. Also, because they deal with XML at a low level, they are also ideally suited to handle the shift to the emerging Web services architecture.

Coherity introduced its Coherity XML Database (or CXD, as it is marketed) for midrange to high-end enterprise customers in March. Its first customer was Hewlett-Packard, and there's enough in CXD to make its adoption understandable. CXD is currently supported on Windows NT/2000, Linux, Solaris, and HP-UX.

At a Glance
	Coherity XML Database (CXD) 3.0