3.8 Conclusion

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eXist's user community has been continuously growing since eXist was released to the public. Applications prove that eXist may be effectively used to implement XML-based services in a wide range of scenarios, dealing with different types of XML documents and data volumes.

Yet much work remains to be done to implement outstanding features. Being an Open Source project, eXist strongly depends on user feedback and participation. Interested developers are encouraged to join the mailing list and share their views and suggestions.

Some of eXist's weak points, namely indexing speed and storage requirements, have already been subject to a considerable redesign. The project is currently concentrating on complete XPath support, possibly using existing implementations developed in other projects. However, XPath has some restrictions. For example, in the current eXist implementation, complex queries involving multiple source documents have to be split manually into several XPath expressions. Additionally, for some types of applications, a more sophisticated transformation of query results is required. XQuery may provide a good alternative to overcome these limitations. It would be worthwhile to invest some work into implementing XQuery for eXist.

Another issue is XUpdate?a standard proposed by the XML:DB initiative for updates of distinct parts of a document. XUpdate is defined as a service in the XML:DB API. However, eXist currently does not implement updates off single nodes in the DOM tree, which is clearly a major restriction for applications using large documents. It is possible to implement the missing functions by extending the basic indexing concepts described earlier.

At the time of writing, we have already started to simplify the created index structures, making them easier to maintain on node insertions or removals. However, some work remains to be done on these issues.


Part IV: Applications of XML