Design Patterns in XML Applications: Part II
Part II: XML-specific patterns
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Table of Contents |
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•Introduction |
Patterns are a useful technique for the transmission of knowledge about recurrent problems in software development. This article, the second of two complementary pieces (see Part I here), is focused on XML-specific patterns as opposed to traditional design patterns in XML specific contexts.
For the first part of this article, some basic knowledge about UML class diagrams will be useful (see our basic UML class diagram guide). For the second part, some basic knowledge of XML DTDs, such as entities, will also be useful.
What are XML patterns?
XML Patterns denotes two kinds of patterns: (1) Program Design Patterns, specifically treating XML-related problems; and (2) Information Structuring Patterns, for the design/implementation of DTDs, schemas etc.
XML patterns of the first kind tend to be compositions and refinements of traditional design patterns. Yet the process of naming and clearly defining them helps in two ways:
- It builds a common base language and base of knowledge for typical XML applications, thus improving understandability, and empowering developers at all levels of expertise.
- It helps XML integrate into the Object Oriented mainstream.
XML patterns of the second kind, those for information design, are focused on finding solutions for common problems in the design of document type definitions (DTDs).
The number of XML patterns is growing quickly, so choosing which ones to present has not been an easy task. I have decided to present here common patterns in the three categories that seem to be most stable in the XML patterns arena: Patterns for Program Design, Patterns for DTD design, and Patterns for DTD Implementation.
XML patterns is a formidable subject, which these articles can only hope to introduce. This article is therefore an invitation to further explore patterns, rather than a catalog of XML patterns. This exploration is not without its pitfalls, which is why I have included a short guide of common misconceptions and warnings at the end of this article. I hope that potential pattern writers can make use of them in order to build a clearer common base of knowledge.
Our tour of XML patterns starts with XML patterns in processing applications, examining the "XMLable" pattern.
