XQuery

Reading the Syntax Diagrams

This book includes syntax diagrams as an option for readers who want a more visual representation of XQuery expression syntax. Each syntax diagram is accompanied by explanatory text and examples. Figure P-1 illustrates the components of a syntax diagram, showing the schema import syntax as an example.

Figure P-1. Example syntax diagram

Rules for interpreting the syntax diagrams are:

• Parts of the diagram in constant width font are literal values. In Figure P-1, import schema and at should appear literally in your query.

• Quotes that appear in syntax diagrams also must appear in your query. Figure P-1 shows that the < namespace-name > must be surrounded by quotes, whereas the < prefix > must not. Either single or double quotes can be used in XQuery, but only double quotes are included in the diagrams for simplicity.

• Where you can specify a value, such as a name, a descriptive name for that value appears in constant width italic and is surrounded by angle brackets. Figure P-1 shows that you fill in the < namespace-name >, < prefix >, and < location > with your own values.

• Multiple options are indicated by parallel lines in the diagram. Figure P-1 shows that you may choose to specify a namespace prefix or default element namespace.

• Optional parts of the expression are indicated by an arrow that bypasses the main arrow. In Figure P-1, it is not necessary to include the namespace < prefix > = or the default element namespace keywords.

• Repeating parts of an expression are indicated by an arrow that returns to the beginning. Figure P-1 shows that you can specify multiple < location >s (preceded by commas) as part of the at clause.