XML and relational databases are tightly woven together in most Web applications. Describe the two distinctly different models XML and relational databases use to structure data.

Question

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Answer 1

The two use distinctly different models to structure data. The relational model used by relational databases is based on two-dimensional tables, which have no hierarchy and no significant order. By contrast, XML is based on hierarchical trees in which order is significant. In the relational model, neither hierarchy nor sequence may be used to model information. In XML, hierarchy and sequence are the main methods used to represent information. This is one of the more fundamental differences between the two models, but there are more.

On Web pages, XML is very useful because the structure of XML closely matches the structure used to display the same information in HTML. Both HTML and XML use tags in similar ways, often creating distinctly hierarchical structures to present data to users. Most of the data for Web pages comes from relational databases and it must be converted to appropriate XML hierarchies for use in Web pages. For these reasons, it makes more sense to see XML as a tool that works in conjunction with databases, rather than as a competitor to them. Major databases support easy-to-use integration with XML.