WG agreed that an implementation note be added to the relevant section to explain the implications for the delimiter scanner if an implementation supports the 'delimited binary' or 'raw byte entity in delimiters' optional features. https://redmine.ogf.org/issues/315 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 From: Steve Hanson/UK/IBM To: mbeckerle.dfdl@gmail.com Cc: DFDL-WG <dfdl-wg@ogf.org>, Andrew Edwards/UK/IBM@IBMGB Date: 16/06/2016 16:02 Subject: Re: Fw: [DFDL-WG] clarification or maybe restriction needed: delimited hexBinary question Mike Your example below should use dfdl:terminator not dfdl:separator but that does not materially change anything. I think it means that the data is raw bytes, no character decoding is happening at runtime. The delimiters are converted to bytes, and the scan is to find those bytes. Correct. However, that leaves off the ability to use delimiters with character class entities, like separator="年%WSP+;" since WSP+ one or more repeats of any of several whitespace characters. It can't just be converted to a sequence of bytes. The IBM DFDL scanner converts everything to bytes, including WSP+ and WSP* delimiters, even when matching characters, so the scan is purely byte-based. Originally this was so a scan handled raw byte entities and parent delimiters with different encodings. This was extended to handle the delimited binary elements erratum - the only difference is that bytes read from the input stream are not converted from an encoding. 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 16/06/2016 09:34 ----- From: Mike Beckerle <mbeckerle.dfdl@gmail.com> To: "dfdl-wg@ogf.org" <dfdl-wg@ogf.org> Date: 15/06/2016 21:41 Subject: [DFDL-WG] clarification or maybe restriction needed: delimited hexBinary question Sent by: "dfdl-wg" <dfdl-wg-bounces@ogf.org> In this example: <xs:element name="foo" type="xs:hexBinary" dfdl:lengthKind="delimited" dfdl:separator="年" dfdl:encoding="UTF-8" /> Note that 年 is 年 which requires 3 bytes in UTF-8: E5 B9 B4 The spec doesn't really say what happens here. It talks about scanning bcd and packed data for delimiters (I think the use case is TLOG format?), but doesn't really talk about what that means. I think it means that the data is raw bytes, no character decoding is happening at runtime. The delimiters are converted to bytes, and the scan is to find those bytes. However, that leaves off the ability to use delimiters with character class entities, like separator="年%WSP+;" since WSP+ one or more repeats of any of several whitespace characters. It can't just be converted to a sequence of bytes. I did not find a restriction in the DFDL spec on what the delimiters can contain when used for delimited binary data. E.g., only raw bytes or no char class entities. Perhaps there is such a restriction and I just didn't find it? If not, perhaps we need such a restriction, just to simplify implementor's lives, and avoid features nobody needs. Consider this: Easy implementation tricks like this don't generalize: <xs:element name="foo" type="xs:hexBinary" dfdl:lengthKind="delimited" dfdl:separator="å¹´" dfdl:encoding="iso-8859-1" /> The separator now contains the 3 bytes of the UTF-8 character, but as individual characters in iso-8859-1 where byte values and unicode codepoints are the same. It doesn't work because char class entities like WSP+ remain problematic. As a UTF-8 WSP+ allows repeats of any of the byte sequences corresponding to these unicode characters: U+0009-U+000D (Control characters) U+0020 SPACE U+0085 NEL U+00A0 NBSP U+1680 OGHAM SPACE MARK U+180E MONGOLIAN VOWEL SEPARATOR U+2000-U+200A (different sorts of spaces) U+2028 LSP U+2029 PSP U+202F NARROW NBSP U+205F MEDIUM MATHEMATICAL SPACE U+3000 IDEOGRAPHIC SPACE I can't express with separator, a repeating disjunction of the byte sequences corresponding to the above. Now, I think all this complexity adds no value for anyone. To avoid all this, I would propose these restrictions on delimited binary data 1) can only use SBCS encodings 2) no repeating char-class entities (WSP*, WSP+) are allowed. With those restrictions I believe the "trick" above of using an iso-8859-1 "decoder", and converting the delimiters into iso-8859-1 character sequences, can be made to work. Comments? ...mikeb 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 -- 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