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It's exactly this kind of thinking that led XML Schema to the position that validation failures are not fatal, they simply cause parts of the document to be marked as invalid. A position which (in the interests of avoiding excessive complexity) the schema-aware XSLT and XQuery specs have not followed through. Michael Kay http://www.saxonica.com/ > -----Original Message----- > From: Bryan Rasmussen [mailto:bry@i...] > Sent: 26 July 2005 15:08 > To: xml-dev@l... > Subject: theories of media languages and error handling > > > There is an assumption one often encounters in > implementations for media (as a > reference media I will focus on hypermedia in the modern > browser), this > assumption is opposition to a general assumption for > validation of data for > media, the media implementation assumption could be put as follows: > > The absence of an object does not cause the failure of the > whole. This means > that as a general rule if I refer to some object that the > browser cannot find > the browser is not designed to fail, the browser assumes that > other objects > that > it can find are still useful to the user and do not present a > faulty instance > to > the user (sometimes of course the browser does fail but such > failures at > missing > components seem always to be due to bugs in the browser and > not required > presence) > > As an example of this assumption - a reference to an image > that the browser > cannot resolve, this is generally the same behavior in printing etc. > > > I am in total aggreement with this assumption. > > The assumption for validation of data for media is often as follows: > > strict requirements for structure prevents failures in your > media presentation. > But of course that someone has put in an element referring to > an image does not > mean the image is placed in the page. > > > > In a way we can define the components of a media instance as > being loosely > coupled. How though has it come to pass that this is so? Is > there any theory out > there or do people have theories? I suppose the pedestrian > reason is that media > itself is dataless and any media format must allow decoupling > of individual > media elements because we cannot know what their meaning is > without the data > context. so that if one had a true xml browser that was > semantically aware we > would be able to crash whenever a document without a required > image was > enquired. > > I am of course aware of the oodles of theory on strict > validation of document > structures and so forth and why failure when data standards > are not held to is > good. I am however sometimes worried that this kind of > strictness is only proper > in some very few instances. > > > > > > > > > > > -- > Bryan Rasmussen > > > > > > > ----------------------------------------------------------------- > 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://www.oasis-open.org/mlmanage/index.php> > >
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