- XML helps join documents, adds editorial comments, places images within text files
- XML is not standardized or a predefined set of tags
- Documents made up of entities, made up of elements, made up of attributes
- Unique identifiers provide cross references between two document points
- Text entities are shorthand for a full name; this makes for more efficient document editing (I assume it saves typing time, too)
- XML documents are best stored in databases
Some information in this article about tag sets is confusing.
Extending Your Markup: An XML Tutorial- XML: tells about content, "a semantic language that lets you meaningfully annotate text"
- Ideal XML document starts with prolog and has one element
- Prolog: XML version + standalone (yes or no) + encoding + DTD declaration
- Element = root of the document, can be nonterminal or terminal
- DTDs: define document structure, specify tag sets, specify tag order, specify tag attributes, can be in XML document or separate
- Element attributes: not required; can be optional, required or fixed
- Namespace: avoids confusion between names
- XML schema and DTDs are still being perfected
W3Schools XML Schema Tutorial
- XML Schema (XSD) can be used instead of DTDs and describes XML document structure
- XSD defines elements, child elements, and attributes
- Why is XSD preferable to DTDs? They are extensible to future additions, support data types and support namespaces.
- XSD supports crosscultural communication because it ensures standard data types (i.e.: date formats of YYYY-MM-DD)
- When elements or attributes have defined data types, invalid types will not be accepted
- Facets = restrictions on XML elements (i.e.: initials field can contain only 3 uppercase letters)
- Seven indicators define order, occurrence and group
This tutorial mentions several data types. I understand date, time and decimal types, but I would like more clarification on string types. Does string just refer to basic text (not numbers, etc.)?
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