Background for discussion on DFDL WG call today. Part of deferred action 242. Regards Steve Hanson IBM Integration Bus, Hursley, UK Architect, IBM DFDL Co-Chair, OGF DFDL Working Group smh@uk.ibm.com tel:+44-1962-815848 mob:+44-7717-378890 ----- Forwarded by Steve Hanson/UK/IBM on 24/05/2016 11:58 ----- From: Steve Hanson/UK/IBM To: dfdl-wg@ogf.org Date: 15/04/2014 15:45 Subject: Fw: [DFDL-WG] Action 242 - valueLength and contentLength function wording I had a quick look at the document and Steve's review comments. The text tries to define valueLength() in terms of the info set value, or states that it is 'calculated from' the infoset value. I believe this will mislead many readers ( it already has done, in fact ). People just assume that the 'value length' is 'the length of the logical value' and they don't think any more deeply about it. So it is absolutely essential to state clearly that this function returns the length of a region in the data stream. It may be simpler to define the behaviour in terms of the length of the simpleContent or complexContent region, minus any padding. The other point is around the bytes/characters issue. Mike's words, or something similar, are definitely required because we don't mandate that the encoding must be consistent throughout a complex type. Nor do we prohibit a mixture of character and non-character content in a complex type. And someone might even call valueLength() with lengthUnits 'characters' on a complex type that contains no character data at all. In principle it would be possible for the value to be available while parsing ( for elements that follow the specified element ). If we are disallowing this then it should be stated very clearly somewhere. And probably is already. regards, Tim Kimber, IBM Integration Bus Development (Industry Packs) Hursley, UK Internet: kimbert@uk.ibm.com Tel. 01962-816742 Internal tel. 37246742 ----- Forwarded by Tim Kimber/UK/IBM on 15/04/2014 15:28 ----- From: Steve Hanson/UK/IBM@IBMGB To: Mike Beckerle <mbeckerle.dfdl@gmail.com>, Cc: "dfdl-wg@ogf.org" <dfdl-wg@ogf.org>, dfdl-wg-bounces@ogf.org Date: 15/04/2014 15:01 Subject: Re: [DFDL-WG] Action 242 - valueLength and contentLength function wording Sent by: dfdl-wg-bounces@ogf.org Review comments added: Regards Steve Hanson Architect, IBM DFDL Co-Chair, OGF DFDL Working Group IBM SWG, Hursley, UK smh@uk.ibm.com tel:+44-1962-815848 From: Mike Beckerle <mbeckerle.dfdl@gmail.com> To: "dfdl-wg@ogf.org" <dfdl-wg@ogf.org>, Date: 11/04/2014 14:04 Subject: Re: [DFDL-WG] Action 242 - valueLength and contentLength function wording Sent by: dfdl-wg-bounces@ogf.org Revised Action 242 proposed changes word doc attached. I have incorporated the discussion in this thread (I hope.) Please review. Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology | www.tresys.com Please note: Contributions to the DFDL Workgroup's email discussions are subject to the OGF Intellectual Property Policy On Tue, Mar 25, 2014 at 10:56 AM, Mike Beckerle <mbeckerle.dfdl@gmail.com> wrote: This language is consistent with what we say for lengthKind pattern in section 12.3.5: "When unparsing, the dfdl:valueLength of a complex type element when the length units is 'characters' is computed as if the entire structure was unparsed into a temporary data stream beginning at position 1, and then this data stream is considered to be text in the character set encoding specified by the dfdl:encoding property, regardless of the actual representation of the complex type element or the elements contained within it. The number of characters in this temporary data stream is the value length of the complex type." The behavior of the IBM DFDL implementation for valueLength is as described is consistent with the above, excepting that it will not detect a decode error, and it gives an SDE (?) if the encoding is not fixed width. Since we have decided not to require that a complex type element is recursively all text all the way down, I believe we have to tolerate implementations having different behaviors in the potentially meaningless cases where there is binary data or encoding changes in the complex type. So I would add to the above suggested language this: "However, if creation of this data stream would cause an encoding error, or parsing of this data stream as characters would cause a decoding error, then the behavior and return value of dfdl:valueLength are implementation dependent." Looking at the DFDL spec, I am concerned that we never really say what we mean by the "length of the ComplexContent region." (Last sentence before Table 7 in section 12.3.7) Section 12.3.7.3 doesn't do it. The dfdl:valueLength function may be the first place where we have to actually say how the various sub-regions contribute to the ComplexContent region's length. I believe this is the obvious "sum of length of all contained regions", but keep in mind that alignment region lengths will vary depending on the starting alignment, so the length is, in general, dependent on the position within the bit stream. Hence when unparsing we have to specify that the dfdl:valueLength is measured as if the ComplexContent region started at position 1 (as I did above) so that internal alignment regions can be given meaningful lengths. The general clarification should be added to 12.3.7.3, or to section 12.3.7 immediately before section 12.3.7.1. Something like this: "The length of the ComplexContent region is the sum of the lengths of the contained regions. However, note that alignment regions inside the ComplexContent may be of different lengths depending on the ComplexContent's starting position alignment." Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology | www.tresys.com Please note: Contributions to the DFDL Workgroup's email discussions are subject to the OGF Intellectual Property Policy On Mon, Mar 24, 2014 at 11:34 AM, Andrew Edwards <andy.edwards@uk.ibm.com> wrote: Steve (et al) - Resending as the last one bounced. I'll usurp Tim and respond :) Currently the IBM implementation insists on using a fixed-length encoding and returns an "unsupported" error message for a variable width encoding. With a fixed width encoding, we "do the maths" using the bytes-per-character and the bytes written by this complex element. HTH, Andy Andy Edwards - IBM Integration Bus - DFDL Email: andy.edwards@uk.ibm.com Snail Mail: MP211, Hursley park, Hursley, WINCHESTER, Hants, SO21 2JN Tel int: 247222 Tel ext: +44 (0)1962 817222 Desk: DE3 V17 The Feynman problem solving Algorithm 1) Write down the problem 2) Think real hard 3) Write down the answer -- Murray Gell-mann in the NY Times Steve Hanson/UK/IBM 24/03/2014 14:52 To "dfdl-wg@ogf.org" <dfdl-wg@ogf.org>, cc Mike Beckerle <mbeckerle.dfdl@gmail.com>, Andrew Edwards/UK/IBM@IBMGB Subject Re: [DFDL-WG] Action 242 - valueLength and contentLength function wording Link Note errata 3.9, my bolding: "3.9. Section 12.3.5, 7.3.1, 7.3.2. The spec originally allows lengthKind ‘pattern’ to be used when the representation of the current element, or of a child element, is binary, but imposes restrictions on the encoding that can be in force. Clarify that the encoding property must be defined for the element (else schema definition error), and that a decoding processing error is possible if the match of the regex encounters data that does not decode in that encoding, dependent on the setting of encodingErrorPolicy. Remove section 12.3.5.1. Same clarifications needed for testKind ”pattern” property for asserts and discriminators. For consistency, the restriction that a complex element of specified length and lengthUnits ‘characters’ must have children that are all text and that have the same encoding as the complex element, is dropped." That's the restriction that I was referring to in my comment below. I can see why it was dropped - basically the parser now just tries to decode n characters using the complex element's encoding (and encodingErrorPolicy). We could apply the same principle for dfdl:valueLength & dfdl:contentLength - you build the stream from the bottom up, and then decode it using the complex element's encoding (and encodingErrorPolicy ?) to get the length in characters. Note that's how unparsing for lengthKind 'prefixed' with lengthUnits 'characters' would work as well - the spec just says "For a complex element, the length is that of the ComplexContent region" which is not sufficient (12.3.4). Similar deal for lengthKind 'explicit' - in order to know the size in chars of ElementUnused the unparser needs to know the size in chars of the data first (12.3.7.3). (Of course, for a fixed width encoding, you don't need to decode, you can just do the maths, but for the general case you need to decode. Also just doing the maths does not take encodingErrorPolicy into account). Regards Steve Hanson Architect, IBM DFDL Co-Chair, OGF DFDL Working Group IBM SWG, Hursley, UK smh@uk.ibm.com tel:+44-1962-815848 From: Steve Hanson/UK/IBM To: Mike Beckerle <mbeckerle.dfdl@gmail.com>, Cc: "dfdl-wg@ogf.org" <dfdl-wg@ogf.org>, dfdl-wg-bounces@ogf.org Date: 24/03/2014 12:55 Subject: Re: [DFDL-WG] Action 242 - valueLength and contentLength function wording Mike 23.5.3.1. Value length is only a function of the dfdl:encoding property if the element has a text representation. Not sure this needs to be (re)stated here. 23.5.3.1. "The value length is computed from the DFDL infoset value, ignoring the dfdl:length or dfdl:textOutputMinLength property. Other DFDL properties which affect the length of a text or binary representation are respected, it is only an explicit length which is ignored." Last sentence is too imprecise - should be phrased in terms of the grammar. 23.5.3.1. "If the second argument is 'characters' then the element must have text representation and it is a schema definition error otherwise". Yes but only for a simple type, so should be qualified. 23.5.3.1. "If the second argument, giving the length units, is 'characters', then recursively, this complex type element must have text representation throughout all its contained elements and framing, all of which must also use a uniform character set encoding." I can't see that restriction elsewhere in the spec when it talks about length of ComplexContent and lengthUnits 'characters' - I was expecting it to be in section 12.3.4 or 12.3.7.3 which face the same issue - but it isn't. Did we decide not to have this restriction? Without such a restriction, how does the unparser come up with a meaningful length (unless it re-parses)? (Tim - what does IBM DFDL do here?) What about delimiters and padding of children that use %#r entities? 23.5.3.2. The points in 23.5.3.1 about escape characters, length as a function of encoding, and bottom up for complex elements, apply equally to 23.5.3.2. It might be easier just to say in 23.5.3.2 that dfdl:contentLength for complex elements is same as dfdl:valueLength, and for simple elements differs only by the additional inclusion of LeftPadding and RightPadOrFill regions. Also noted in passing: Specified length - An item has specified length when dfdl:lengthKind is "implicit", "explicit", or "prefixed". should be Specified length - An element has specified length when dfdl:lengthKind is "implicit" (simple type only), "explicit", or "prefixed". Regards Steve Hanson Architect, IBM DFDL Co-Chair, OGF DFDL Working Group IBM SWG, Hursley, UK smh@uk.ibm.com tel:+44-1962-815848 From: Mike Beckerle <mbeckerle.dfdl@gmail.com> To: "dfdl-wg@ogf.org" <dfdl-wg@ogf.org>, Date: 20/03/2014 17:21 Subject: [DFDL-WG] Action 242 - valueLength and contentLength function wording Sent by: dfdl-wg-bounces@ogf.org See attached doc which is proposed revisions to section 23.5.3 Mike Beckerle | OGF DFDL Workgroup Co-Chair | Tresys Technology | www.tresys.com Please note: Contributions to the DFDL Workgroup's email discussions are subject to the OGF Intellectual Property Policy [attachment "Action-252-DFDL-Functions-23.5.3.docx" deleted by Andrew Edwards/UK/IBM] -- dfdl-wg mailing list dfdl-wg@ogf.org https://www.ogf.org/mailman/listinfo/dfdl-wg Unless stated otherwise above: IBM United Kingdom Limited - Registered in England and Wales with number 741598. Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU Unless stated otherwise above: IBM United Kingdom Limited - Registered in England and Wales with number 741598. Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU [attachment "Action-252-DFDL-Functions-23.5.3.docx" deleted by Steve Hanson/UK/IBM] -- dfdl-wg mailing list dfdl-wg@ogf.org https://www.ogf.org/mailman/listinfo/dfdl-wg Unless stated otherwise above: IBM United Kingdom Limited - Registered in England and Wales with number 741598. Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU -- dfdl-wg mailing list dfdl-wg@ogf.org https://www.ogf.org/mailman/listinfo/dfdl-wg Unless stated otherwise above: IBM United Kingdom Limited - Registered in England and Wales with number 741598. 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