ressources: http://www.w3schools.com/xquery/default.asp
	reference: http://www.w3schools.com/xquery/xquery_reference.asp

xpath:
	nodename
	root: /
	all matching descendants: //
	current: .
	parent: ..
	select attributes: @attr
	predicates:
		[pred], [1], [last()-1], [position()<3], [@lang], [@lang='eng'], [price>35.00]
	wildcards:
		any element: *
		any attribute: @*
		any node: node()
	several paths: p1 | p2
	axes: axisname::nodetest[predicate]
		ancestor, ancestor-or-self, attribute, child, descendant, descendant-or-self, following, following-sibling, namespace, parent, preceding, preceding-sibling, self
	operators:
		| + - * div = != < >= > >= or and mod

select: doc("books.xml")/bookstore/book[price>30]/title
	flwor:
		for $x in select_query
		where $x/predicate
		order by $x/xpath
		return $x/xpath
		html:
			<ul>
			{
			for $x in doc("books.xml")/bookstore/book/title
			order by $x
			return <li>{data($x)}</li>
			}
			</ul>
	conditional statements:
		for $x in doc("books.xml")/bookstore/book
		return if ($x/@category="CHILDREN")
		then <child>{data($x/title)}</child>
		else <adult>{data($x/title)}</adult>
	modify result:
		add elements/add attributes:
			return <li class="{data($x/@category)}">{data($x/title)}. Category: {data($x/@category)}</li>
	for:
		for $x in (1 to 5)
		for $x at $i in doc(...
		let $x := (1 to 5)
	functions:
		built-in: http://www.w3schools.com/xpath/xpath_functions.asp
			uppercase()
			substring(str,start,len)
		user-defined functions:
			declare function prefix:function_name($parameter AS datatype)
			AS returnDatatype
			{
				...
			}

check: xlink, xpointer