3096 2006-04-07 20:58:30 +0000 Are components side-effect free? 2011-02-23 20:27:04 +0000 1 1 1 Unclassified XML Processing Model Pipeline language unspecified PC Linux CLOSED FIXED decided P2 normal --- 1 Norman.Walsh ndw avernet innovimax+w3c oldest_to_newest 9085 0 Norman.Walsh 2006-04-07 20:58:30 +0000 Can implementations cache the results of evaluating a component with a particular set of inputs and parameters? Should this be something that can be declared about individual components? 9094 1 innovimax+w3c 2006-04-08 17:23:43 +0000 A simple answer to the question "Are components side-effect free?" is "Not always", so we should be able to mention it. How and where is the point of discussion for me 9214 2 Norman.Walsh 2006-04-13 15:29:24 +0000 Discussed (without resolution): http://www.w3.org/XML/XProc/2006/04/13-minutes.html 9221 3 avernet 2006-04-13 16:53:42 +0000 From our call today, my understanding of the question is: Given a pipeline that contains among other things 2 steps, both executing the same component, with the same set of inputs, should a pipeline implementation guarantee that for a given execution of that pipeline, the output documents of those two steps are always the same? My take on it: Will people write pipelines with two invocations of XSLT on the same input document with the same stylesheet? I don't see this as a frequent enough use case that would warrants us burdening pipeline implementations with having to guarantee that the second invocation returns the same output as the first one. Alex 9306 4 innovimax+w3c 2006-04-19 15:41:51 +0000 I'm requiring a definition of what we call side effects, because it seems like some usable side effects makes no problem in the pipeline (repeatable side effects) and that using information about date and time which aren't side effects could make some problems In conclusion, it looks like side effects and caching are not so obviously tighted problems 9317 5 avernet 2006-04-20 01:33:34 +0000 Mohamed: My understanding is the question is stated in comment #3: Given a pipeline that contains among other things 2 steps, both executing the same component, with the same set of inputs, should a pipeline implementation guarantee that for a given execution of that pipeline, the output documents of those two steps are always the same? Norm: is this a fair way to put it? 9561 6 Norman.Walsh 2006-05-02 20:42:43 +0000 27 Apr 2006: http://www.w3.org/XML/XProc/2006/04/27-minutes.html The following proposal was accepted: We say that all components are non-functional. That is, a pipeline implementation must behave as if it evaluated a component every time it occurs. "Must behave as if" is spec-ease for "implementations that are clever enough to determine with certainty that a component is, in fact, functional are free to cache the intermediate results because by golly if it is, no one will be able to tell 9586 7 Norman.Walsh 2006-05-03 20:45:13 +0000 Implemented in langspec.xml $1.7$.