[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Namespace and Versioning
"Bullard, Claude L (Len)" wrote: > > ... What I was looking for initially > in this thread is some comments on the practices > people are using to see if any general cases > emerge. ... > to that point i can describe the method we implemented to handle versions of encoding specs from the Kassenaerztlichebundesvereinigung (KBV). (they're the group in germany which sets standards on electronic data interchange within the health industry.) they have the habit of every several years bringing out a new standard. often enough, the new standard ascribes different meanings to the various terms which were present in the previous standard. there are also cases in which the same term has different meanings in distinct contemporaneous standards. the implementation domain was lisp, so the name-management was built on the package system. each namespace was modeled as a package. each name was modeled as a symbol. each symbol was associated with the appropriate processing method. the package system provides mechanisms to control identity relationships between names. this both in terms of inheritance relations between packages and in terms of specific assertions regarding individual symbols. each KBV version was associated with a package. the package names, and thus the namespace names were, in fact, chosen to reflect the relations among versions, but that was immaterial to the implementation. the package relations were arranged such that terms for which the meaning changed were associated with distinct symbols in the respective version's packages. terms for which the meaning had not changed were carried over from the older version's package to the newer version's by "inheriting" the respective symbol from one package to the next. it was much easier to do than to describe. the moral is, you need the means to control relations between namespaces; the namespace names themselves may well serve documentary ends, but are, in fact, secondary.
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