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Subject: Re: [ubl-ndrsc] Containers: R116
I'd like to elaborate on Lisa's initiation of the discussion. As LC plans to implement NDR checklist for 1.0, and time is running short, supporting or differing opinions should be heard very soon. Otherwise, downstream work will get stuck. So members of the list please kindly respond. If there is no consensus, or no proposed responses to the questions, or simply no discussions, then it may be necessary to remove this rule from the NDR checklist and defer containership altogether until the time the issues reach further maturity. On Fri, 27 Jun 2003, Lisa-Aeon wrote: >>... >>The questions still outstanding are: >> >>1. Why are there so many container types as opposed to one generic UBL one? >>This has been answered, but would like to see rationale behind it. It was not stated how containers are to be implemented from reading the latest NDR Checklist, but from discussions done in the past, the assumed implementation appears to be one container type per 1..n type element declaration. This results in many container types, as essentially all 1..n types will have twice the schema types. And if 0..n gets implemented similarly, then all 0..n types will also have twice the schema types. Why do we need so many container types that load up the UBL processor's memory and slow things down? The rationale behind such proliferation of container types is not satisfactorily explained. This is especially so when these container types are just carriers that contribute nothing to the model. A simpler solution could be used to reduce this "80%-resource-usage/20%-work-done" situation. A single container type that permits any type can be a solution to all locations where containers are needed. This has the implication that the schema validator part of UBL processor need not do that much validation work with the entire container containing the list of elements as a whole. Instead, as the list of elements in the instance space will need to be looped through for processing anyway, individual elements will have to be visited again during list step-through, thus presenting another opportunity for validation of individual list elements. >>2. 0..n has not been addressed. Previous discussion ended somewhat with the deferral to NDR Chair to decide whether to open up this topic for discussion. It is necessary for 0..n's case to be rounded up and fully explored side-by-side the 1..n case in order for implementation of containers to be systematic and symmetric. This is obvious from the fact that 0..n instance can easily become 1..n as soon as one element is instantiated. So ignoring this 0..n issue is not a satisfactory treatment of the containership solution to me. This topic has been opened. Please kindly respond with a proposal for 0..n that is symmetric in treatment to 1..n. >>3. The way to implement list containers. It seems to be assumed that >>container tags will be generated on the fly. There is conflict in the way >>this is assumed. Discussion has it that there is one type for each list, >>where are these types in schema? It is not clear from reading the NDR checklist how the mechanism of implementing containers should be carried out by UBL processors. On one hand, the multiply-typed containers mentioend but disagreed in (1) seem to suggest that multiple schema types be defined for the containers. This is presumably a result of overloading the schema validator portion of a UBL processor to also validate containers with all its list elements as a whole. If containers are validated by schema validators, then we'll need the proposer of containership to define the schemas and describe means to merge in a non-conflicting way with existing non-containered schemas. Email correspondences, on the other hand, appear to suggest (and please correct me if I'm mistaken in summarizing here) that containers are not part of the model and thus do not appear in the UBL schemas. If they're implemented on the fly, then all the more we need detailed specifications on what on-the-fly implementation can/cannot/must/must-not/shall/shall-not do to containers and their list elements. How do the two expectations reconcile with each other? Best Regards, Chin Chee-Kai SoftML Tel: +65-6820-2979 Fax: +65-6743-7875 Email: cheekai@SoftML.Net http://SoftML.Net/
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