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October 11, 2003


David Locke

As to the meaningless of the text contained by an XML tag, keep in mind that all content on a computer is meaningless. Without the conventions that define data types and instructions, and the computational power used to act on the assumptions of type, computing couldn't happen.

Markup isn't the only computing device that separates content from presentation. Processor instructions define the presentation of the memory content within the processor itself. Cache decoherence separates the temporal context of the content from processor presentation. Hypertransport moves data via instructions and goes one further by packetizing the content and instructions. You might say it creates a tag, where the instructions are attributes and the data is serialized between the header tag and the trailer tag.

The maintenance of context is job one in computing at all levels. Content and presentation are only one on the screen.

David Locke

Contrary to the author of the webpage associated with the first link, XML markup is semantic markup. The concept of semantic markup originated in SGML. This semantic markup is the value provided by the ease of knowing which meaningless chunk of text was an instance of a particular kind like title, abstract, or etc.

The quickest way to see the value of semantic markup is to ask how much computational power would have to be applied if the text wasn't marked up semantically. How many pattern recognition programs were written in the history of A.I.

This semantic markup may not be all that rich, but it is rich enough to present a task allocation boundary between man and machine. And, it puts the machine in the role of helping man rather than replacing man.

Semantics is an onion. Container-based semantic markup is the base layer of the intended semantics.

As for serialization, narrative is the norm for man. Narrative is expressed in a language constrained by a grammar. Bacus-Naur Form describes grammar, not schema. It should come as no surprise that XML is a grammar, not a schema.

Schema capabilities are an extension to XML. I was very surprised that database tables express a grammar. But, if XML can be used as a schema, then this conclusion must be valid. Not being a linguist, I'm wondering if linguists use ER diagrams to define the languages they study.

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