IF Blocks

IF blocks have a single input port, labeled condition; a Flow port; and two result ports: if then, and if else.

Figure 254. IF Block

You use IF blocks to compose if then, else XQuery expressions, such as the following:


`<Book>` `{` `if( $book/title ) then` `<Title/>` `else` `<ISBN/>` `}` `</Book>`

This expression, for example, was composed by mapping

The title element in the source document to the IF block's input port.

The if then result port to the Title element in the target structure.

The if else result port to the ISBN element in the target structure.

IF blocks create a structure if the if then or if else branches are true. These ports can be connected to the target schema; otherwise they can be connected to Flow ports of FLWOR, function, and other IF blocks.

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