RE: () equivalent to () ?
> You mean that the static type of "()" is void(), while for > "data()" it is > "xdt:anyAtomicType()*"? Could you elaborate? What impact in > practice does > this difference in static types, whatever it is, have? It probably affects XQuery more than XPath or XSLT: in an XQuery implementation that does the full (pessimistic) static typing, an expression such as [data(()) | *] is going to fail statically, because the operands of "|" have to be sequences of nodes. But XPath and XSLT are also allowed to do early type checking, and Saxon for example will give you a warning on this expression, or at least, on others that are very similar. For example if you declare <xsl:variable name="d" select="data(*)"/> <xsl:value-of select="$d | *"/> you'll get a compile-time warning that the expression can succeed only in the special case where $d is an empty sequence. The typing of empty sequences is a pretty esoteric subject, full of traps for the unwary. A system that does static typing (even the optimistic kind) can distinguish (treat differently) an "empty sequence of integers" and an "empty sequence of strings", but to a system without static typing they are indistinguishable. Michael Kay http://www.saxonica.com/ > > > > > > However, testing this theory in practice in a host language > > > such as XSLT 2.0 > > > is impossible(?) since all comparison operators returns the > > > empty sequence > > > when an operand is the empty sequence. > > > > You're talking about a new comparison operation of your own > invention which > > you haven't fully defined, and which seems to differ > slightly from those > > already defined in the language. You're welcome to do this. > First you need > > to define what you want its semantics to be, and then you > can implement it > > as a function. But so far, you haven't defined its > semantics except by > > appeal to "common principles" - which you will quickly find > are not as > > common as you thought. > > Right, the question was ill prepared and badly put, there's > not much more to > say. > > > Cheers, > > Frans
PURCHASE STYLUS STUDIO ONLINE TODAY!
Purchasing Stylus Studio from our online shop is Easy, Secure and Value Priced!
Download The World's Best XML IDE!
Accelerate XML development with our award-winning XML IDE - Download a free trial today!
Subscribe in XML format