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Problem: simple format that is impossible to model
by Mike Beckerle 03 Oct '19

03 Oct '19

I have a dead-simple little format: data/data/data/data data/data/data/data it is lines of "/" separated strings. All elements are optional. I simply want this: data//data to round trip. For that to happen I need it to parse into <field>data</field><field></field><field>data</field> That is, I require that empty field element in the middle to be created and put into the infoset. I can find no way to do this. The strings have no initiator/terminator, so dfdl:emptyValueDelimiterPolicy is not relevant. All the elements are optional, so default values aren't relevant. The spec states: 9.4.2.2 Simple element (xs:string or xs:hexBinary) Required occurrence: If the element has a default value then an item is added to the infoset using the default value, otherwise an item is added to the Infoset using empty string (type xs:string) or empty hexBinary (type xs:hexBinary) as the value. Optional occurrence: If dfdl:emptyValueDelimiterPolicy is not 'none'[12] <https://daffodil.apache.org/docs/dfdl/#_ftn12> then an item is added to the Infoset using empty string (type xs:string) or empty hexBinary (type xs:hexBinary) as the value, *otherwise nothing is added to the Infoset*. There are errata/actions to clarify wording here around dfdl:emptyValueDelimiterPolicy being in effect or not (because there is no initiator/terminator for it to use as opposed to the property in isolation just being 'none'). But that doesn't change anything about this issue. If this very simple format is not possible, then we need a property or new property enum value that makes it possible. Thoughts? 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 <http://www.ogf.org/About/abt_policies.php>

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RFC 2119 word usage in DFDL Spec
by Mike Beckerle 30 Sep '19

30 Sep '19

In studying Tracker 304 https://redmine.ogf.org/issues/304 I have found that there are many uses of words like must and should, which are not specifically in accord with the notions of RFC 2119, because they are not involved in statements about requirements. For example, in section 2.3.1.1 Usually, the behavior of the unparser is symmetric to the behavior of the parser; however, there are cases where the DFDL schema will accept several equivalent representations for the same logical data. In this case it would be ambiguous which of these equivalent representations should be produced by the unparser. The DFDL standard contains representation properties which are used to eliminate this ambiguity. It is a schema definition error if a DFDL schema is being used to unparse data and there is any ambiguity about the representation. We can either ignore such issues, because the context doesn't require us to consider this a requirement statement, or reword so as to avoid RFC2119 terms. I am not sure it is worth changing this prose in all the places where this sort of thing happens. The word 'should' is less problematic than the word 'must' of which there are hundreds of occurrences. Thoughts? 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 <http://www.ogf.org/About/abt_policies.php>

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Re: [DFDL-WG] DFDL pointer & offset proposal
by Bradd Kadlecik 25 Sep '19

25 Sep '19

Properties for indirection: The following properties allow for data to be accessed in a non-sequential or non-contiguous format by using indirection values to locate the data contents. When parsing, the indirection value is used to access the contents in the data stream to populate the infoset. When unparsing, an indirection value is created to store the contents in the data stream when creating the data stream from the infoset. The indirection value does not exist in the infoset, but only in the data stream. The LeadingAlignment and TrailingAlignment regions apply to the indirection value in the data stream. The initiator and terminator as well as all regions between the LeftFraming and RightFraming regions are applied to the data content accessed through the indirection value. Property Name | Description ----------------------+-------------------------------------------------------- indirectKind | Enum | | Specifies the type of indirection value used to | access the the contents in the data stream. | | Valid values ‘pointer’, ‘offset’, ‘none’. | | ‘pointer’ means a numeric value gives an | implementation-dependent starting position of the | content. | | ‘offset’ means a numeric value that when added to | indirectBase gives the starting position of the | content. | | ‘none’ means no indirection is used and is the | default value. | | Annotation: dfdl:choice, dfdl:element, dfdl:group, | dfdl:simpleType, dfdl:sequence ----------------------+-------------------------------------------------------- indirectType | QName | | Name of a simple type derived from xs:integer or any | subtype of it. | | This type, with its DFDL annotations specifies the | representation of the indirection value. | | It is a schema definition error if the xs:simpleType | specifies any of: | · dfdl:lengthKind 'delimited', 'endOfParent', or | 'pattern' | · dfdl:lengthKind 'explicit' where length is an | expression | · dfdl:outputValueCalc | · dfdl:initiator or dfdl:terminator other than | empty string | · dfdl:alignment other than '1' | · dfdl:leadingSkip or dfdl:trailingSkip other | than '0'. | | Annotation: dfdl:choice, dfdl:element, dfdl:group, | dfdl:simpleType, dfdl:sequence ----------------------+-------------------------------------------------------- indirectBase | String | | Provides the relative path to a prior element upon | which the offset is based. | | Required only when dfdl:indirectKind is ‘offset’. | | Annotation: dfdl:choice, dfdl:element, dfdl:group, | dfdl:simpleType, dfdl:sequence ----------------------+-------------------------------------------------------- indirectEmptyValue | Integer | | Specifies the indirection value that indicates when | the data content is empty. If this property is | specified, all underlying elements must contain a | default value specification or it is a schema | definition error. | | Annotation: dfdl:choice, dfdl:element, dfdl:group, | dfdl:simpleType, dfdl:sequence The following example illustrates how to describe a pointer to a null-terminated string (common in languages like C). <xs:element name="myString" type="xs:string" dfdl:lengthKind="delimited" dfdl:encoding="UTF-8" dfdl:terminator="%NUL;" dfdl:indirectKind="pointer" dfdl:indirectType="ptr32_t" dfdl:indirectEmptyValue="0" default=""/> <xs:simpleType name="ptr32_t" dfdl:representation="binary" dfdl:lengthKind="explicit" dfdl:length="4" dfdl:byteOrder="bigEndian"> <xs:restriction base="integer"/> </xs:simpleType> The data stream may look like the following for a string value of “test”. Location Hex values 00000000 0012A000 0012A000 7465737400 t e s t The following example defines an array of 3 pointers to complex elements defined by ns0:myStruct. <xs:element name="myArray" type="ns0:myStruct" dfdl:lengthKind="implicit" dfdl:indirectKind="pointer" dfdl:indirectType="ptr32_t" dfdl:indirectEmptyValue="0" minOccurs="3" maxOccurs="3" dfdl:occursCountKind="fixed"/> <xs:simpleType name="ptr32_t" dfdl:representation="binary" dfdl:lengthKind="explicit" dfdl:length="4" dfdl:byteOrder="bigEndian"> <xs:restriction base="integer"/> </xs:simpleType> The data stream may look like the following with the contents of each occurrence in a different location and the contents of the 2nd occurrence being empty. Location Hex values 00000000 00147000 00000000 00146000 00146000 ... 00147000 ... The following example defines an offset to a 6 byte hexBinary value with the offset being calculated from the start of the current element. <xs:element name="myData" type="xs:hexBinary" dfdl:lengthKind="explicit" dfdl:length="6" dfdl:indirectKind="offset" dfdl:indirectType="uint" dfdl:indirectBase="."/> <xs:simpleType name="uint" dfdl:representation="binary" dfdl:lengthKind="explicit" dfdl:length="4" dfdl:byteOrder="bigEndian"> <xs:restriction base="unsignedInt"/> </xs:simpleType> The data stream may look like the following for a hexBinary value of “123456789ABC”. Location Hex values 00000100 00000108 00000208 123456789ABC Regards, Bradd Kadlecik z/TPF Development Phone: 1-845-433-1573 2455 South Rd E-mail: braddk(a)us.ibm.com Poughkeepsie, NY 12601-5400 United States

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OGF DFDL WG Call on 2018-09-26 - cancelled
by Steve Hanson 25 Sep '19

25 Sep '19

Apologies but I have a deadline coming up and not able to do anything DFDL WG related right now. Regards Steve Hanson Architect, IBM DFDL Co-Chair, OGF DFDL Working Group Hursley, UK smh(a)uk.ibm.com tel:+44-1962-815848

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Re: [DFDL-WG] DFDL inputValueCalc restrictions
by Michele Zundo 25 Sep '19

25 Sep '19

I’m also not seeing coming from in dfdl-wg... > On 25 Sep 2019, at 16:25 , Beckerle, Mike <mbeckerle(a)tresys.com> wrote: > > ((( > Strangely, this thread not showing up on dfdl-wg(a)ogf.org. > but is coming to me direct at my tresys email because I am directly addressed also. > > Bradd are you getting bounce-back from the OGF mail system? > > I'll respond here, but I'd prefer that this happen on the ogf dfdl-wg(a)ogf.org email list. > ))) > > > Daffodil project has been building up an experience document about inputValueCalc, outputValueCalc, and hidden groups. The draft is on our wiki here: > > https://s.apache.org/daffodil-experience-with-computed-elements <https://s.apache.org/daffodil-experience-with-computed-elements> > > This will get finalized into an OGF Experience document and a number of changes/corrections to the DFDL spec will come out of it I expect. > > We already have identified that disallowing IVC and OVC on the same element is unnecessary and sometimes you want this. Your case with default values sounds similar. > > We can incorporate your contribution to the experience document. Take a look and see if the existing discussion can just be enhanced with a sentence about also allowing default on an IVC element. If so I can edit and add it there. > From: Bradd Kadlecik <braddk(a)us.ibm.com> > Sent: Wednesday, September 25, 2019 9:48 AM > To: dfdl-wg(a)ogf.org <dfdl-wg(a)ogf.org> > Cc: Steve Hanson <smh(a)uk.ibm.com>; Beckerle, Mike <mbeckerle(a)tresys.com>; Michele Zundo <michele.zundo(a)esa.int>; Liam O'Neill <WILONEIL(a)uk.ibm.com>; DFDL Schemas for Commercial and Scientific Data Formats <smhdfdl(a)gmail.com> > Subject: DFDL inputValueCalc restrictions > > Hello, > > I have one item I'd like to discuss at some point regarding inputValueCalc and not allowing the default property to be specified. I have a use case where the default property would be useful for unparse. It makes perfect sense to not allow it for outputValueCalc however. > > The use case is in forming a connection between an inputValueCalc element and an outputValueCalc element where the incoming document might not contain the inputValueCalc element for unparse and a default value would be desired for the outputValueCalc use. This is an item our customers using DFDL would like to make use of but don't want to require the element to always exist for unparse. > > Regards, > > Bradd Kadlecik > z/TPF Development > Phone: 1-845-433-1573 > E-mail: braddk(a)us.ibm.com <mailto:braddk@us.ibm.com> > 2455 South Rd > Poughkeepsie, NY 12601-5400 > United States > >

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Cancelled: OGF DFDL Working Group call
by Steve Hanson 25 Sep '19

25 Sep '19

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clarifications needed for %ES; and %WSP*; entities
by Mike Beckerle 18 Sep '19

18 Sep '19

Currently, we have gaps in the spec. E.g., in discussion of dfdl:initiator, the spec says %ES; cannot appear alone in the list, but there is nothing prohibiting one from just using dfdl:initiator="%ES;%ES;" or dfdl:initiator="%ES: %ES;" to trivially work around this constraint, even though both of these definitions are nonsense. To avoid repeated discussion of this topic for each of initiator, terminator, and separator, these statements need to be made where ES and WSP* are defined, or in some other central location that discusses DFDL String Literals and whitespace separated lists thereof. %ES; can never appear as part of any other token. I.e., "%ES;A" is the same as just "A" regardless of what "A" is. So %ES; can only appear as a solitary token in a whitespace separated list of delimiter tokens or nilValue tokens. Furthermore, %ES; cannot be repeated in the list, since "%ES; %ES;" means the same thing as just "%ES;". %WSP*; similarly cannot be repeated in the list meaningfully, so that should be prohibited as well. (In fact repeating any token multiple times in the list can be prohibited.) %WSP*; cannot be combined with %WSP+;, as the combination is equivalent to just %WSP+; by itself. Furthermore %WSP*;%WSP*; means the same as %WSP*; alone, so that should also be prohibited. If we add these clarifications, then statements about how %ES; and %WSP*; and their specific constraints for dfdl:initiator and dfdl:terminator and dfdl:separator need not repeat these statements, and the constraints they express do not have obvious gaps. 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 <http://www.ogf.org/About/abt_policies.php>

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pointers and offsets - BDDL
by Mike Beckerle 30 Aug '19

30 Aug '19

This is a link to a format description language (proprietary) which mentions a pointers/offsets capability. http://www.binarydom.com/sdk/doc/bddl.shtml We may want to review this w.r.t. DFDL capabilities being considered in this area. There aren't too many of these to draw from in standardization. I am trying to get the Tresys one (which is not part of Daffodil) into form where we can describe it here also. 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 <http://www.ogf.org/About/abt_policies.php>

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Action 313: Plus '+' sign and lax textNumberCheckPolicy
by Mike Beckerle 30 Aug '19

30 Aug '19

Looks like ICU changed behavior.... From: Steve Lawrence <slawrence(a)apache.org> Sent: Thursday, August 29, 2019 1:30 PM To: users(a)daffodil.apache.org Subject: Re: Plus '+' sign and lax textNumberCheckPolicy - was: Re: How to model a fixed-length integer that may be padded with space on the left? I think this is a difference in ICU version? A little grepping through ICU source, I found a change [1] to their number parsing logic in Dec 2017: + if (!isStrict) { + parser.addMatcher(WhitespaceMatcher.getInstance()); + parser.addMatcher(new PlusSignMatcher()); + } That looks to me like a change to make it so plus signs are always matched in lax/lenient mode regardless of the pattern (Daffodils current behavior). A couple minor changes have been made to that section, but nothing that allows you to turn if off if lenient is on. It's hard to tell in the git history what release that was in, but it looks like around version 61, which is relatively new (Daffodil is on version 62). Also, the latest version of DecimalFormatProperties.java (looks to be an internal implementation, so no online javadocs), has javadocs that states that plus signs are always allowed in lenient/lax mode [2]. I think this is a change in ICU behavior in newer versions. - Steve [1] https://github.com/unicode-org/icu/commit/68340c8464bd988477d6c88f46f9dfe45… [2] https://github.com/unicode-org/icu/blob/master/icu4j/main/classes/core/src/…

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Cancelled: OGF DFDL Working Group call
by Steve Hanson 29 Aug '19

29 Aug '19

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