- dfdl-wg - lists.ogf.org

How to express semantics of unordered groups
by Mike Beckerle 01 Nov '06

01 Nov '06

I'd like to consider this concept as a way to express the semantics in DFDL of unordered groups. The approach is to use source language transformation. Here's an example of an unordered sequence of 2 elements: <xs:element name="n1"> <xs:complexType> <xs:sequence dfdl:unordered='true' separator=","> <xs:element name="s1" type="string" dfdl:initiator="s1:" /> <xs:element name="s2" type="int" dfdl:initiator="s2:"/> </xs:sequence> </xs:complexType> </xs:element> We explain what this means by indicating that it behaves like this rewrite: <xs:element name="n1"> <xs:annotation><xs:appinfo source=....> <dfdl:format validation="cardinality(./s1) <= 1 & cardinality(./s2) <= 1"/> </xs:appinfo></xs:annotation> <xs:complexType> <xs:sequence' separator=","> <xs:choice> <xs:sequence> <xs:element name="s1Initiator" type="xs:string" fixed="s1:"/> <xs:element name="s1" type="xs:string" /> </xs:sequence> <xs:sequence> <xs:element name="s2Initiator" type="xs:string" fixed="s2:"/> <xs:element name="s2" type="xs:int" /> </xs:sequence> <xs:sequence />  </xs:choice> <xs:choice> <xs:sequence> <xs:element name="s1Initiator" type="xs:string" fixed="s1:"/> <xs:element name="s1" type="xs:string" /> </xs:sequence> <xs:sequence> <xs:element name="s2Initiator" type="xs:string" fixed="s2:"/> <xs:element name="s2" type="xs:int" /> </xs:sequence> <xs:sequence />  </xs:choice> </xs:sequence> </xs:complexType> </xs:element> The above is probably missing a DFDL annotation indicating that the discrimination of the choice is done using the s1Initiator and s2Initiator fields based on their parsing correctly w.r.t. their fixed value facet. In XSD, unordered sequences (aka "all" groups) also have the semantics that each element can occur only zero or 1 time. This is modeled by the additional validation constraint you find at the top of the rewritten form. This isn't the only choice for semantics of unordered groups of course, but it is one coherent position on it. I think it is very attractive to reduce the issue of initiator-based unordered sequences to choice and discrimination, since we need those constructs no matter what. Comments? ...mikeb

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DFDL telcon in half an hour
by Westhead, Martin (Martin) 25 Oct '06

25 Oct '06

I have some things I need to get to today I can only join for the first 20-30 mins. Call Details Time: 9am PDT Number: 1-800-664-0771 At the automated answering system, press 0 for the operator. Ask for the "Daffodil working group" call.

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DFDL Telcon tomorrow
by Westhead, Martin (Martin) 11 Oct '06

11 Oct '06

Call Details Time: 9am PDT Number: 1-800-664-0771 At the automated answering system, press 0 for the operator. Ask for the "Daffodil working group" call.

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Telcon tomorrow
by Westhead, Martin (Martin) 04 Oct '06

04 Oct '06

I'm afraid I cannot make it to the meeting again tomorrow - sorry. Call Details Time: 9am PDT Number: 1-800-664-0771 At the automated answering system, press 0 for the operator. Ask for the "Daffodil working group" call.

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contact
by Angelo Doty 24 Sep '06

24 Sep '06

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hello
by Sue Fontenot 21 Sep '06

21 Sep '06

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Delivery failure
by postmaster＠sklad10.ogf.org 21 Sep '06

21 Sep '06

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Re: [DFDL-WG] DFDL and Multi-dimensional arrays - just say no to them?
by Westhead, Martin (Martin) 20 Sep '06

20 Sep '06

My first reaction is this: If we are confident that we have the necessary hooks/extensibility mechanisms that multi dimensional arrays can be defined in all their glory as a supplement. Then it is very easy to say no. Another tack on this is the following. I do not think that we need to support arbitrary array representations in XML. However we do need to be able to describe the data format including metadata such as array dimensions etc. So I would push to go a little farther than your 1d array and say we need to define a way to describe the multidimensionality of your 1d array. Likewise it would be really good to have metadata to capture the description of sparse representations... Martin _____ From: dfdl-wg-bounces(a)ogf.org [mailto:dfdl-wg-bounces@ogf.org] On Behalf Of Mike Beckerle Sent: Wednesday, September 20, 2006 10:17 AM To: dfdl-wg(a)ogf.org Subject: [DFDL-WG] DFDL and Multi-dimensional arrays - just say no to them? I'd like to solicit opinions on this suggestion: We have been assuming we needed more than just 1d array support, but this is now unclear. We've pushed back on "top-down" use of XML Schemas, i.e., DFDL must be used bottom up, and transformation into the "logical form you wanted" is not our job. That is, the DFDL Schema's logical organization is constrained (heavily) by the data format. We could take an exactly analogous position with respect to multi-dimensional or other complex arrays. The DFDL describes the representation, and the sttructure of the DFDL schema will end up matching the shape of the representation of the array. Transforming that into something that looks and acts like a ordinary dense multi-dimensional array is a transformation that is out-of-scope for us. E.g., if the array is stored as a run-length encoded vector, then it is DFDL's job to describe this run-length encoded vector, but not to project/transform it so that it can be accessed in a manner that hides the run-length encoding and makes it look like an ordinary dense array. (I actually believe hiding sparse array implementations behind a dense-array facade is generally not advised. Algorithmically you must operate on the sparce representation anyway for efficiency. ) Suggested Conclusion: we can just say that we don't do multi-dimensional arrays because it is out-of-scope for us. Comments? ...mikeb

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DFDL and Multi-dimensional arrays - just say no to them?
by Mike Beckerle 20 Sep '06

20 Sep '06

I'd like to solicit opinions on this suggestion: We have been assuming we needed more than just 1d array support, but this is now unclear. We've pushed back on "top-down" use of XML Schemas, i.e., DFDL must be used bottom up, and transformation into the "logical form you wanted" is not our job. That is, the DFDL Schema's logical organization is constrained (heavily) by the data format. We could take an exactly analogous position with respect to multi-dimensional or other complex arrays. The DFDL describes the representation, and the sttructure of the DFDL schema will end up matching the shape of the representation of the array. Transforming that into something that looks and acts like a ordinary dense multi-dimensional array is a transformation that is out-of-scope for us. E.g., if the array is stored as a run-length encoded vector, then it is DFDL's job to describe this run-length encoded vector, but not to project/transform it so that it can be accessed in a manner that hides the run-length encoding and makes it look like an ordinary dense array. (I actually believe hiding sparse array implementations behind a dense-array facade is generally not advised. Algorithmically you must operate on the sparce representation anyway for efficiency. ) Suggested Conclusion: we can just say that we don't do multi-dimensional arrays because it is out-of-scope for us. Comments? ...mikeb

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DFDL Telcon tomorrow
by Westhead, Martin (Martin) 20 Sep '06

20 Sep '06

Agenda * Discuss ongoing document edits. * Review ongoing actions: Action: [Geoff] Put together a first pass description Action: [Mike] Look at DCGs Action: [Tom] Modifications to the scoping section. Call Details Time: 9am PDT Number: 1-800-664-0771 At the automated answering system, press 0 for the operator. Ask for the "Daffodil working group" call.

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