I've spent today catching up with the recent DFDL spec discussions around Simon's comments to v0.19. Some comments of my own on the content of these and previous call minutes.

- General principle: The eventual consumers of DFDL will be users the majority of whom will not be data modelling experts, that's certainly the experience at IBM. Most see data modelling as a black art and find it difficult. I think that an over-reliance on hidden elements is not going to go down well. I would err on the side of caution here, and only if we are convinced a property will be very rarely used should we remove it and replace by a hidden element.
[Simon] Accepted, providing we can specify everything. Ideally we'll publish a rigorous, orthogonal language and a convenient, intuitive library with controlled redundancy.

- Leading/Trailing Skip Bytes is a property intended to handle the byte skipping added by compilers, over and above simple byte alignment rules. The formulae for setting the values is beyond the ken of users to set manually, it would invariably be done using an automated COBOL -> DFDL translator, etc. I would not be too troubled if that went 'hidden'.

'finalTerminatorCanBeMissing' property. The rules for interpreting what trailing markup actually means are complex and properties like this will almost certainly be needed. (Aside: For Mike's second example, though, where data of max length n is terminated by markup only if actual length < n, wouldn't that be better expressed using a regular expression? finalTerminatorCanBeMissing is too general, and could lead the parser to validly parse data where the terminator was accidentally omitted).

- Infix/prefix/postfix separators. I believe this should be retained. It's in IBM WTX (Mercator) and I frequently have to apologise for the absence of postfix in IBM MRM. When a user sees (eg) x,y,z it's easier for him to comprehend that the comma after z is a postfix separator rather than the terminator of the parent group.

- Simon had a comment on the removal of 'applies' which I haven't seen discussed ("I find this cumbersome. I suggest this alternative: drop ‘applies’ and ‘dfdl:format’, insist on ‘dfdl:sequence’ and friends instead, and add local variants like ‘dfdl:sequenceLocal’. For attribute shorthand, add boolean attributes with the same name: sequenceLocal=”true” (optional, default false)."). I don't follow, the use of 'applies' is orthogonal to whether you use dfdl:format or one of the specific elements such as dfdl:sequence.
[Simon] You're right, the ideas should be discussed separately. My hasty comment throws it all in together.

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