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Xyleme: An interesting conjunction

Technically, Xyleme is usually thought of as an XML database. However, this is not accurate in a variety of ways, writes Phil Howard of

Market Analysis

Xyleme: An interesting conjunction
The name of Xyleme is derived from the word xylem, which is the collective name for the cells, vessels and fibres that making up the woody part of a tree. That is, those parts that draw up nutrients from the roots and provide them to the leaves and other growing parts of the tree. The company (which is French) considers this to be a good metaphor for what Xyleme does, in that it stores XML-based data but focuses on its ability to turn this into useful information.

Technically, Xyleme is usually thought of as an XML database. However, this is not accurate in a variety of ways. First, Xyleme refers to its product, which actually consists of Xyleme Zone Server plus a software development kit, as a content mart. By this the company means that it provides the textual equivalent of a data mart. However, Xyleme differs from a data mart in that it aims not just to provide query capability against textual data but that it aims to provide the facilities you would need to re-deploy this information (such as queries, application development and third party text mining). So, for example, the company targets publishers (as well as Global 500 accounts) that want to be able to reuse content in multiple publications, say.

This positioning as a content mart also raises the question of how this differs from content management. The difference is one of emphasis. Content management is mostly about the creation of content, whereas Xyleme is more about its re-deployment and re-use.

Another difference that Xyleme brings to the table is that it does not believe that there is any such thing as unstructured data. Of course this is a conceptual view but from its perspective even text has metadata that describes it (title, author, version and so on); if it is in XML format then it will have a hierarchy; and then there may be references to other data. All of things imply structure: there is just more or less of it.

Some other interesting features of Xyleme are the way that it combines XML, relational and object oriented technology. For example, it implements views, which are essentially the same as the logical views of heterogeneous data that are implemented in relational databases.

The other major quasi-relational feature of Xyleme is that it uses an SQL-like language for queries. The reason it does so, as opposed to using XQuery, is quite simply that anyone familiar with SQL will only need minimal training to pick up the necessary extensions, whereas the use of XQuery will mean learning a whole new environment.

The other interesting facet of Xyleme's query language, at least for database historians, is that it is based on what used to be OQL, which was the query language developed by O2 for use with its eponymous database. Of course, O2 disappeared into the maw of what used to be Ardent and although some parts of it were reused within what is now Ascential's MetaStage, the product itself ceased to be marketed. As it turns out, the founders of Xyleme (or, at least, some of them) were from O2. They seem to have done a good job.

Copyright 2003. Originally published by, reprinted with permission. provides IT decision makers with free daily e-mails containing news analysis, member-only discussion forums, free research, technology spotlights and free on-line consultancy. To register for a free e-mail subscription, click here.

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