"David Thielen" <david@bogus.windward.net> wrote in message
news:2DBE4A4A-E130-4656-BEAD-D8747783FEF9@microsoft.com...[color=blue]
> Hello;
>
> Is this correct to say:
> "/order/software" or "software" in each case is an axis specifier[/color]
No, Axis specifier can be only a predefined (full) name out of 13 axis names
(see below) or an abbreviated axis specifier (just "@").
[color=blue]
> while "."
> is an abbreviated step?
>
> I had thought both were a way of specifing a node and therefore were an
> axisSpecifier.[/color]
No.
The rules from the spec:
[5] AxisSpecifier ::= AxisName '::'
| AbbreviatedAxisSpecifier
[6] AxisName ::= 'ancestor'
| 'ancestor-or-self'
| 'attribute'
| 'child'
| 'descendant'
| 'descendant-or-self'
| 'following'
| 'following-sibling'
| 'namespace'
| 'parent'
| 'preceding'
| 'preceding-sibling'
| 'self'
[13] AbbreviatedAxisSpecifier ::= '@'?
[color=blue]
>
> Also, any good book(s) or website(s) that explain this, preferably by
> example?[/color]
Michael Kay's books on XSLT 1.0, XSLT 2.0 and XPath 2.0
http://www.amazon.com/gp/product/186...lance&n=283155
http://www.amazon.com/gp/product/076...lance&n=283155
http://www.amazon.com/gp/product/076...lance&n=283155
Jeni Tennison's books on the same topics.
http://www.amazon.com/gp/product/159...lance&n=283155
http://www.amazon.com/gp/product/076...lance&n=283155
http://www.amazon.com/gp/product/159...lance&n=283155
Hope this helped.
Cheers,
Dimitre Novatchev.
[color=blue]
>
> --
> thanks - dave
> david_at_windward_dot_net
>
http://www.windwardreports.com
>
>
>
> "Dimitre Novatchev" wrote:
>[color=green]
>>
>> "David Thielen" <david@bogus.windward.net> wrote in message
>> news:DA492C31-ACA4-4280-8A88-78C729376EAA@microsoft.com...[color=darkred]
>> > Hi;
>> >
>> > First, thanks for helping on this I really appreciate it.
>> >
>> > Ok, I see that the xpath must start with "." to get it to the node and
>> > the
>> > "[...]" then modifies that - makes sense.
>> >
>> > But then, shouldn't ".[.='software']" or "./.[.='software']" or[/color]
>>
>> No, the syntax rules do not allow this:
>>[color=darkred]
>> >> [4] Step ::= AxisSpecifier NodeTest Predicate*
>> >> | AbbreviatedStep[/color]
>>
>> as we can see, Predicatecan only occur after a NodeTest , not after an
>> AbbreviatedStep.
>>[color=darkred]
>> > "./[.='software']" work.[/color]
>>
>> Again, Predicate cannot be the leftmost symbol in a step
>>[color=darkred]
>> >
>> > In the case of ".[.='software']" isn't that saying start with the node
>> > "."
>> > (which exists) and then return all where .='software'?[/color]
>>
>> This may seem a clear semantics, but the syntax is invalid according to
>> the
>> XPath 1.0 grammar rules.
>>
>> As I said, use:
>>
>> self::node()[.='software']
>>
>>
>>
>> Cheers,
>> Dimitre Novatchev
>>[color=darkred]
>> >
>> > --
>> > thanks - dave
>> > david_at_windward_dot_net
>> >
http://www.windwardreports.com
>> >
>> >
>> >
>> > "Dimitre Novatchev" wrote:
>> >
>> >>
>> >> "David Thielen" <david@bogus.windward.net> wrote in message
>> >> news:24EA7468-C52A-4765-B556-1EE1DCF81F1B@microsoft.com...
>> >> > Hello;
>> >> >
>> >> > I assumed it is invalid syntax. My question is why? I don't
>> >> > understand
>> >> > why
>> >> > "[.='software']" or some variation of that is invalid.
>> >>
>> >> Read the XPath 1.0 Spec.
>> >>
>> >> It says:
>> >>
>> >>
http://www.w3.org/TR/xpath#predicates
>> >>
>> >> "A predicate filters a node-set with respect to an axis to produce a
>> >> new
>> >> node-set. For each node in the node-set to be filtered, the
>> >> PredicateExpr
>> >> is
>> >> evaluated with that node as the context node, with the number of nodes
>> >> in
>> >> the node-set as the context size, and with the proximity position of
>> >> the
>> >> node in the node-set with respect to the axis as the context position;
>> >> if
>> >> PredicateExpr evaluates to true for that node, the node is included in
>> >> the
>> >> new node-set; otherwise, it is not included."
>> >>
>> >>
>> >>
>> >> So, a predicate can only apear after some XPath expression and filters
>> >> it. A
>> >> predicate, alone, is not a valid XPath expression.
>> >>
>> >> This is also made clear if we look at the BNF grammar definition of
>> >> XPath
>> >> 1.0. Of all rules only rule [4] and rule [20] contain the nonterminal
>> >> symbol
>> >> predicate and it is always not the leading symbol (of the RHS):
>> >>
>> >>
>> >>
>> >>
http://www.w3.org/TR/xpath#section-Location-Steps
>> >>
>> >>
>> >> [4] Step ::= AxisSpecifier NodeTest Predicate*
>> >> | AbbreviatedStep
>> >>
>> >>
>> >>
>> >>
>> >>
http://www.w3.org/TR/xpath#node-sets
>> >>
>> >>
>> >>
>> >> [20] FilterExpr ::= PrimaryExpr
>> >> | FilterExpr Predicate
>> >>
>> >>
>> >>
>> >>
>> >> I hope that this answers completely your question.
>> >>
>> >>
>> >> Cheers,
>> >> Dimitre Novatchev
>> >>
>> >>
>> >>
>> >> >
>> >> > --
>> >> > thanks - dave
>> >> > david_at_windward_dot_net
>> >> >
http://www.windwardreports.com
>> >> >
>> >> >
>> >> >
>> >> > "Dimitre Novatchev" wrote:
>> >> >
>> >> >> > // these all fail - WHY?
>> >> >>
>> >> >> because of a common feature -- they all have invalid XPath syntax.
>> >> >>
>> >> >> > try
>> >> >> > {
>> >> >> > rtn = nav.SelectSingleNode("[.='software']");
>> >> >> > }
>> >> >> > catch (XPathException ex)
>> >> >> > {
>> >> >> > Console.Out.WriteLine("[.='software'] exception = " +
>> >> >> > ex.Message);
>> >> >> > }
>> >> >> > try
>> >> >> > {
>> >> >> > rtn = nav.SelectSingleNode("./[.='software']");
>> >> >> > }
>> >> >> > catch (XPathException ex)
>> >> >> > {
>> >> >> > Console.Out.WriteLine("./[.='software'] exception = " +
>> >> >> > ex.Message);
>> >> >> > }
>> >> >> >
>> >> >> > // yes this works - but I need the node as it does have a value.
>> >> >> > object obj = nav.Evaluate(".='software'");
>> >> >> > Console.Out.WriteLine(".='software' evaluate = " + obj);
>> >> >>
>> >> >>
>> >> >> Try:
>> >> >>
>> >> >> "self::*[.='software']"
>> >> >>
>> >> >> or
>> >> >>
>> >> >> "string(self::*[.='software'])"
>> >> >>
>> >> >> depending on whether you need the node or its string value
>> >> >> returned.
>> >> >>
>> >> >>
>> >> >> Cheers,
>> >> >> Dimitre Novatchev
>> >> >>
>> >> >>
>> >> >>
>> >> >>
>> >> >>
>> >> >> "David Thielen" <david@bogus.windward.net> wrote in message
>> >> >> news:741F026C-54CD-4B6D-BDD8-0FA03A7E06D1@microsoft.com...
>> >> >> > Hi;
>> >> >> >
>> >> >> > I am sure I am missing something here but I cannot figure it out.
>> >> >> > Below
>> >> >> > I
>> >> >> > have a program and I cannot figure out why the xpath selects that
>> >> >> > throw
>> >> >> > an
>> >> >> > exception fail. From what I know they should work.
>> >> >> >
>> >> >> > Also the second nav.OuterXml appears to also be wrong to me.
>> >> >> >
>> >> >> > Can someone explain to me why this does not work? (This is an
>> >> >> > example
>> >> >> > from
>> >> >> > a
>> >> >> > program we have where xpath can be entered in two parts so we
>> >> >> > have
>> >> >> > to
>> >> >> > be
>> >> >> > able
>> >> >> > to handle this. We can't just always require the fill
>> >> >> > /order/product[.='software'].)
>> >> >> >
>> >> >> > Program below sig.
>> >> >> >
>> >> >> > --
>> >> >> > thanks - dave
>> >> >> > david_at_windward_dot_net
>> >> >> >
http://www.windwardreports.com
>> >> >> >
>> >> >> > Program.cs:
>> >> >> > using System.Xml;
>> >> >> > using System.Xml.XPath;
>> >> >> > using System;
>> >> >> > using System.IO;
>> >> >> >
>> >> >> > namespace XPathSample
>> >> >> > {
>> >> >> > class Program
>> >> >> > {
>> >> >> > static void Main(string[] args)
>> >> >> > {
>> >> >> >
>> >> >> > string xml =
>> >> >> > "<order>" +
>> >> >> > "<product>software</product>" +
>> >> >> > "<product>software</product>" +
>> >> >> > "</order>";
>> >> >> > XPathDocument doc = new XPathDocument(new StringReader(xml));
>> >> >> >
>> >> >> > // this works
>> >> >> > XPathNavigator nav = doc.CreateNavigator();
>> >> >> > XPathNavigator rtn =
>> >> >> > nav.SelectSingleNode("/order/product[.='software']");
>> >> >> > Console.Out.WriteLine("nav(/) = " + nav.OuterXml);
>> >> >> > Console.Out.WriteLine("/order/product[.='software'] = " +
>> >> >> > rtn.OuterXml);
>> >> >> >
>> >> >> > // this works although the nav.OuterXml appears wrong
>> >> >> > nav = nav.SelectSingleNode("/order");
>> >> >> > rtn = nav.SelectSingleNode("product[.='software']");
>> >> >> > Console.Out.WriteLine("nav(/order) = " + nav.OuterXml);
>> >> >> > Console.Out.WriteLine("product[.='software'] = " + rtn.OuterXml);
>> >> >> >
>> >> >> > // this works (same as prev)
>> >> >> > rtn = nav.SelectSingleNode("./product[.='software']");
>> >> >> > Console.Out.WriteLine("./product[.='software'] = " +
>> >> >> > rtn.OuterXml);
>> >> >> >
>> >> >> > nav = nav.SelectSingleNode("product");
>> >> >> > Console.Out.WriteLine("nav(/order/product) = " + nav.OuterXml);
>> >> >> >
>> >> >> > // these all fail - WHY?
>> >> >> > try
>> >> >> > {
>> >> >> > rtn = nav.SelectSingleNode("[.='software']");
>> >> >> > }
>> >> >> > catch (XPathException ex)
>> >> >> > {
>> >> >> > Console.Out.WriteLine("[.='software'] exception = " +
>> >> >> > ex.Message);
>> >> >> > }
>> >> >> > try
>> >> >> > {
>> >> >> > rtn = nav.SelectSingleNode("./[.='software']");
>> >> >> > }
>> >> >> > catch (XPathException ex)
>> >> >> > {
>> >> >> > Console.Out.WriteLine("./[.='software'] exception = " +
>> >> >> > ex.Message);
>> >> >> > }
>> >> >> >
>> >> >> > // yes this works - but I need the node as it does have a value.
>> >> >> > object obj = nav.Evaluate(".='software'");
>> >> >> > Console.Out.WriteLine(".='software' evaluate = " + obj);
>> >> >> >
>> >> >> >
>> >> >> > Console.Out.WriteLine("all done");
>> >> >> > }
>> >> >> > }
>> >> >> > }
>> >> >> >
>> >> >> >
>> >> >>
>> >> >>
>> >> >>
>> >>
>> >>
>> >>
>> >>[/color]
>>
>>
>>[/color][/color]
Why does this xpath fail - starting over