Good point, I've always understood the "root" to be the single node that is set as the context. Maybe I'm wrong and your comparison to a file system make senses. However, if you take the file system example and map a directory to a drive then you have a new root that it isn't really a true root in the real physical sense - this is similar to setting a new context in Jaxen. One final point, if XPath should be able to handle document fragments (which I think it should) then there is not always a Document root in a fragement so "/" would be invalid. Eddie ----- Original Message ----- From: "James Strachan" <[EMAIL PROTECTED]> To: "Eddie" <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]> Sent: Tuesday, November 20, 2001 11:12 AM Subject: Re: [Jaxen] Paths beginning with / should start from document?
> Hi Eddie > > Thanks for that. I guess thats my question; should the 'root' be the context > node on which the XPath expression evaluates or should 'root' always be the > document? (Lets not worry about document fragments for this discussion) > > I always thought it should be the document, otherwise the use of "/" at the > start of an expression adds no extra value. Lets take an example. > > <foo c="123"> > <bar> > <x> > <y>hello</y> > </x> > </bar> > </foo> > > Lets say we get access to the <bar> element. (Using dom4j code for a > second). > > Node bar = document.selectSingleNode( "/foo/bar" ); > > Now typically if I wanted to navigate relative to the <bar> element I'd just > use a relative XPath expression which does not start with "/". > > Node y = bar.selectSingleNode( "x/y" ); > > There's no need for me to start the expression with "/" since the XPath > expression will start from <bar> anyway as its relative. > > However if I wanted to get access to the c attribute, I could do > > Node c = bar.selectSingleNode( "/@c" ); > > Couldn't I? > > i.e. the addition of "/" to the front of the XPath expression means use the > document as the root, not the node I happen to be evaluating the expression > on, which is <bar>. If the "/" means use the evaluation context as the root > then there is no difference between "/@c" and "@c" which would seem pretty > pointless to me. > > Is my understanding correct here? There does seem to be a bit of confusion > on this topic. > > James > ----- Original Message ----- > From: "Eddie" <[EMAIL PROTECTED]> > To: "James Strachan" <[EMAIL PROTECTED]> > Sent: Tuesday, November 20, 2001 10:02 AM > Subject: Re: [Jaxen] Paths beginning with / should start from document? > > > > James, > > if an XPath starts with a "/" then it is an absolute path and is taken as > > meaning the root node. The "root" is usually the Document node but doesn't > > necessarily need to be. It could be just the root of a particular branch. > > The root is defined by the context that you set before evaluation using > the > > method Context.setNodeSet(List nodeSet). I'm not sure what is supposed to > > happen if you have no root but several top level nodes. You probably get > an > > exception or an empty result set. > > Hope this helps > > Eddie > > > > > > ----- Original Message ----- > > From: "James Strachan" <[EMAIL PROTECTED]> > > To: "Jaxen-Interest" <[EMAIL PROTECTED]> > > Sent: Tuesday, November 20, 2001 9:26 AM > > Subject: [Jaxen] Paths beginning with / should start from document? > > > > > > > Just a quick clarifcation that I wanted to double check with the list. > Any > > > XPath expression that starts with "/" should always start from the > > document > > > of the node on which the XPath is evaluated, shouldn't it? > > > > > > i.e. the behaviour is like a file system where whatever directory (node) > > you > > > evaluate a path expression, anything starting with "/" starts from the > > root > > > directory (the document). > > > > > > This is true isn't it? > > > > > > James > > > > > > > > > _________________________________________________________ > > > Do You Yahoo!? > > > Get your free @yahoo.com address at http://mail.yahoo.com > > > > > > > > > _______________________________________________ > > > Jaxen-interest mailing list > > > [EMAIL PROTECTED] > > > https://lists.sourceforge.net/lists/listinfo/jaxen-interest > > > _________________________________________________________ > Do You Yahoo!? > Get your free @yahoo.com address at http://mail.yahoo.com > _______________________________________________ Jaxen-interest mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/jaxen-interest
