[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Global or shared namespace?
If it's global it applies to everything, including any namespaces declared. If it's shared it applies only to the namespaces it's shared with. I guess that's what you'd call a namespace link (ln -s share andsharealike). It's a typeof, it's not a typeof, it's a similar typeof (typesof nothing - null, false, empty, 0). It's undefined so it's a typeof undefined. It can be really tough figuring out if something isn't there because it isn't there to see. You really have to put something there to make the point that nothing is there. What I don't see is the context. In the outake below a lack thereof (namespace) can make something undefined. But I think, from the orignal message by Eric van der List the context is not in code but in describing it. In code I'd personally prefer to see a null rather than a "" or a http://notanamespace/. I'll make it "" if I have to show someone it isn't there because it looks alot better than null on the screen. But sometimes, just to be clear I might say "The selection you made is invalid." or "There is no whatever you asked for available." If it's a problem in some particular context making an explicit declaration as below to ensure no conflict seems like a good solution. A problem would problem arise if someone said: xsd:double double and someone else came along and said double But then someone could just as easily duplicate mydouble:double by accidentally working at the same location and not reading the code. So if the namespace is undefined and you define it, then someone else defines it with the same definition but it means something different.... Or we could do the other extreme and null mynull:null yournull:null and give different names to the same thing. All to make it clear there's nothing there. What's needed is nice clear definition like the famous: "If it's not internal, it's external." by adding the third qualification "If it's not explicit and it's not implicit, it's undefined." From the XML Schema spec (3.4): "The consequence of not declaring a target namespace in a schema is that the definitions and declarations from that schema, such as USAddress and purchaseOrder, are referenced without namespace qualification. In other words there is no explicit namespace prefix applied to the references nor is there any implicit namespace applied to the reference by default." "In cases where a schema is designed without a target namespace, it is strongly recommended that all XML Schema elements and types are explicitly qualified with a prefix such as xsd: that is associated with the XML Schema namespace (as in po.xsd). The rationale for this recommendation is that if XML Schema elements and types are associated with the XML Schema namespace by default, i.e. without prefixes, then references to XML Schema types may not be distinguishable from references to user-defined types." ----- Original Message ----- From: "Ronald Bourret" <rpbourret@r...> To: <xml-dev@l...> Sent: Wednesday, November 28, 2001 6:39 AM Subject: Re: Global or shared namespace? > Michael Kay wrote: > > > Just to add to the terminological morass, XPath 1.0 and XSLT 1.0 refer to > > such elements and attributes as having "an expanded name with a null > > namespace URI". > > > > Whether any distinction was intended between "a name with no namespace URI" > > and "a name with a null namespace URI", I really don't know! > > If there is, it's a bug. > > -- Ron > > ----------------------------------------------------------------- > The xml-dev list is sponsored by XML.org <http://www.xml.org>, an > initiative of OASIS <http://www.oasis-open.org> > > The list archives are at http://lists.xml.org/archives/xml-dev/ > > To subscribe or unsubscribe from this list use the subscription > manager: <http://lists.xml.org/ob/adm.pl> >
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