[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] RE: XML CMM and ISO9000 compliance? - was A standard approach
You're right. For some systems, some proofs are worth paying for. The question is which ones? Would it have been more useful for NASA to have proven its low level engineers wrong about the potential damage to the carbon edges or for the low level engineers to have proven such damage is possible? The first set would have been cheaper and answered the more immediate question of what is the best course of action next. The second set proves that what was theorized was possible and probable. Nothing more. Given outcomes, I would have preferred the first set of proofs. For any proof to be meaningful, it must make a difference to a choice of value. It must reduce uncertainty. For proofs of XML to be valuable, we should know what choices we are making. It comes back to what is to be proven given the axioms of the system and the rules for changing theorems to produce new but consistent theorems if we are talking about formal systems. In fact, XML relies heavily on the Draconian rule for rejecting non-well formed strings. That's one level. What is proven? It doesn't prove XSLT will operate as intended because XSLT operates on the infoset. Does it prove that a correctly implemented XML parser can construct a valid infoset? What about operations on strings? Is XSLT proven to be lossless? At what level? One of the interesting issues of formal systems is how long one can avoid discussing reality, the isomorphisms where meaningfulness is found. As long as one is only discussing the system that is defined by XML 1.0, one can do that virtually forever. The proofs one would look for in your example are in the applications. Because applications such as XSLT, XML Schema, XQuery and XPath are used throughout the XML systems, proofs of these should be of interest to all. len From: Dave Pawson [mailto:dpawson@n...] The military do. E.g. 'prove' all paths through a program. Any stack based language fails on this basis, hence Z was born as a KISS language, to run on risc processors which were sufficiently simple to enable 'proof' of this nature. Or at least that's what the UK MoD tell us :-) Mind you, it gets kind of critical when 'proving' the launch software for a missile leaving an airplane wing :-)
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