[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Patterns - What is it?
Dan Mabbutt wrote: > The first group is represented by the page http://www.xmlpatterns.com/. A > brief review of this page and some of the references on it suggest that a > "Pattern" is sort of a "best practice" or "archetype software algorithm." An "design pattern" is ultimately a literary form, used to capture experience by forcing certain answers to certain questions about a topic to be provided. The form is loose. Design patterns were developed for architecture, but they have had a major impact on object-oriented programming. When you read someone writing "this is a visitor class" or "that is a factory method" they are refering to a well-known design pattern. The reason design patterns are important is that without establishing a common vocabulary there really can be no XML "professionals". Without such a vocabulary, people will attempt to use a secondary vocabulary, which will usually be OO or databases or HTML; those vocabularies may include enough baggage that they may allow communication while preventing understanding. For example, one of the most basic patterns is the one variously called the "document skeleton" or "document shell": that is the simple structure that whenever information units grow to a certain level of size or have a strong semantic or processing cohesiveness compared to the outside material, we will see a common structure thing - head (with metadata) - body (with data) At the lowest level, this is actually supported in the element tag syntax, but it scales all the way up so that documents will often be structured at the highest level in a similar way. I think Fabio has a design pattern for this at www.xmlpatterns.com It is such a common pattern, but I doubt that if we asked people on XML-DEV or any of the W3C working groups what that was called, that we would get a recognised term. Without such a controlled vocabulary, discussions are forced to start from the beginning with actual examples: this is such a burdon that it prevents discussion of issues. This will only get worse as more people con on board who cannot write content models: not only will it be difficult to write prose, but difficult to write formal notations. Rick Jelliffe
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