Is this how DFDL started?

["Costello, Roger L." <co...@mitre.org>]

Hi Folks,

Is this correct:


  *   XML Schema is a language for describing one data format --> the XML data format.
  *   When the DFDL working group began (circa 2000), they looked around and saw that XML Schema is a language for describing one data format. They noticed that XML Schema was designed to be expanded (via foreign attributes). So, they decided to use XML Schema as the starting point for a new data format description language. The working group expanded XML Schema such that the expanded language could describe any data format.

Re: Is this how DFDL started?

["Beckerle, Mike" <mb...@tresys.com>]

It went like this to my recollection.....

IBM already had a product in the market in the late 1990s or early 2000's which customers liked which used annotated XML Schema for a format description language. XML was trendy and popular at the time, so that concept of leveraging XML schema for the logical structure but standardizing the format annotations was a very easy one to grab onto. It was almost a foregone conclusion. There was some resistance to XML schema notationally, (Pretty hard to put on a powerpoint slide because it's so verbose.), but there was no other standard BNF form, and XML was a bit of a juggernaut in those days.

I would also like to comment on your analogy of XML Schema is to XML as DFDL Schema is to other data.

I agree with this and  it works to some degree. You use XML Schema with XML, you use DFDL Schema with other data. They're both data tools.  Maybe that's all you were after in your analogy. In which case I'm entirely fine with it.

I tend to describe them as apples and oranges - similar because they're both edible fruits, but quite different in other ways.

E.g., to me saying XML Schema describes XML data is a stretch. Really the XML specification describes the format, and code libraries like Xerces implement the format directly and XML Schema aren't involved.  An XML Schema only covers logical structure, not how to tokenize, how the syntax is escaped, etc. Furthermore  you can use XML data without using an XML schema, and lots of people do that.

So I offer this sort of flipped analogy:

XML Schema defines the high-level logical structure stuff, and re-uses already defined low-level stuff (via XML parser for the data syntax) for the nitty-gritty details.

DFDL Schema defines the low-level stuff (via DFDL properties for the data syntax) for the nitty-gritty. and re-uses already defined high-level logical structure stuff (XML Schema)

Not sure that helps the point you were trying to make, but there's maybe something useful about it.

-mikeb

________________________________
From: Costello, Roger L. <co...@mitre.org>
Sent: Monday, December 23, 2019 11:40 AM
To: users@daffodil.apache.org <us...@daffodil.apache.org>
Subject: Is this how DFDL started?


Hi Folks,



Is this correct:



  *   XML Schema is a language for describing one data format --> the XML data format.
  *   When the DFDL working group began (circa 2000), they looked around and saw that XML Schema is a language for describing one data format. They noticed that XML Schema was designed to be expanded (via foreign attributes). So, they decided to use XML Schema as the starting point for a new data format description language. The working group expanded XML Schema such that the expanded language could describe any data format.