IBM Version 5 manual Quantifiers, Filtering

other holdings, include the author:

FOR $h IN //holding

RETURN <holding>

$h/title,

IF $h/@type = "Journal" THEN $h/editor

ELSE $h/author </holding> SORTBY (title)

Quantifiers

Sometimes we have to test if elements exist that must satisfy a condition.

Find titles of books in which both sailing and windsurfing are mentioned in the same paragraph:

FOR $b IN //book

WHERE SOME $p IN $b//para SATISFIES contains($p, "sailing")

AND contains($p, "windsurfing") RETURN $b/title

Eg 12. Find titles of books in which sailing is mentioned in every paragraph.

FOR $b IN //book

WHERE EVERY $p IN $b//para SATISFIES contains($p, "sailing")

RETURN $b/title

Filtering

This filter function takes two operands, each of which is an expression that evaluates to a ordered set of notes, and returns copies of some of the nodes in the first operand, while preserving their hierarchic and sequential relationships. The second operand is the filter that trims the hierarchical tree. Both operands must have the same node, not only two nodes of the same value. If the two operands do have a common root, the result of the filter function is an empty list.

The following example illustrates this process by computing a table of contents for a document, which contains many levels of nested sections. The query filters the document and retaining only section elements, title elements nested directly inside section elements, and the text of those title elements. Other elements, such as paragraphs and figure titles, are eliminated, leaving only the skeleton of the document.

The first argument of filter is the root of a document, and the second argument is a path expression that identifies the nodes to be preserved from the original document.

44 The XML Files: Development of XML/XSL Applications Using WebSphere Studio