Hierarchical Data

A lot of real life data is hierarchical. Some are naturally hierarchical, like a family; others are classifications, like the folders in windows explorer. Either way, this data can be quite complex. Hierarchical data is best represented as a tree because of its ability to present the complexity in an easy to understand manner.

In data driven software, hierarchical data is often stored in a database, and presented in a tree control. Most tree controls will accept XML as data. You can retrieve hierarchical data from most databases in XML format. However the shape of this XML is hardly ever compatible with that required by the tree control, requiring transformation of the data XML to a shape acceptable by the tree control. One approach is to use XSLT to effect this transformation.

This requires the developer to develop an XSLT file. However, many developers find it hard to develop in a declarative language such as XSLT.

In this article, we discuss how to:
1. retrieve hierarchical data from the SQL Server 2005 database as XML data, using Common Table Expressions or CTE.
2. develop an XSLT to transform this XML into a shape acceptable to the tree controls. We will develop XLSTs for the ASP.NET 3.5 tree control and a custom tree based on the article Advanced UI Design Using XML and XSL. The code download also has an example of an ExtJs tree.

Download the article and the code here. [Click on the file name and click the Save As button.]

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Download the code [http://www.mediafire.com/?xmm2xjzmxjv].