1) XSL (Extensible Stylesheet Language) is intended to define the formatting and presentation of XML documents for display on screen.
2) XSL processed the XML document in two stages, first is a structural transformation in which elements are grouped, selected and reordered. And then a formatting process in which the resulting elements are rendered as ink on paper, or pixels on the screen.
3) These two stages are quite independent, so XSL was split into two parts: XSLT for defining transformations; and “the reset” – which is still officially called XSL.
4) XPath acts as a sublanguage within an XSLT stylesheet. An XPath expression may be used for numerical calculations or string manipulations, or for testing Boolean conditions.
5) Mostly used to identify parts of the input document to be processed. For example the following instruction outputs the a average price of all the books in the input document.
<xsl: value-of select=”avg(//book/@price)”>
Here avg is the function And //book/@price – first “/” represents starting of the document and /book represents book node of the document and @price represents property of the book node.