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Q: With XML Schema, why do some facets work with some simple types and some don't?

A: The logic of XML Schema facets can only work on simple types that make sense. For example, you could ask XML Schema to constrain a number to be within a minimum or maximum, but you cannot ask it to do so for a word (there isn't a universal sense of min / max for a word).

Here is a list of facets, and the simple types with which they work:

Q: Can you explain what an XML namespace is and how it's used?

Q: I am enjoying your book but wanted to address something in your chapter on XPath Patterns and Expressions that needs clarification. On page 42, on your second tip, you say that by typing * (an asterisk) you select all the current node's children, but don’t you mean that 'element_name/*' will select all the current node’s children?

Q: In chapter 1, Writing XML, you point out that when nesting XML elements, each must be completely enclosed in another otherwise the XML document will not be considered well-formed. If an XML document is not well-formed, will it still work?

Q: On page 5 (see below) you wrote, "An attribute's value must always be enclosed in either matching single or double quotation marks." But in your example, you used a file, not a value.

A: That's a good observation. The term "value" is used here in the generic sense of the word, meaning the information stored in the attribute. It does not mean a numeric value, or even a number.

Q: I know I should know this already since I know HTML well enough, but what exactly is a markup language?

A: A markup language is simply a set of symbols (in HTML and XML, they are called tags) that convey specific information about the text being marked up. For example, a markup symbol could convey how text is supposed to be displayed or processed, or what the text’s context or purpose is.

XML: Visual QuickStart Guide, Examples

Here are some questions people have had while reading this book (with answers supplied when you click on each). If you have a question that you'd like to send me, please visit my Contact page.

Q: With XML Schema, why do some facets work with some simple types and some don't?

Q: Can you explain what an XML namespace is and how it's used?