Re: [xml-dev] It's too late to improve XML ... lessons learned?

[Michael Kay <mike@saxonica.com>]

Some features of XML (most notably XML entities) could have 

been removed from XML 1.0.  But I do not think that entities 

(with the exception of internal parsed entities) have caused 

significant problems. 

I think the security concerns over external parsed entities are probably one of the major factors that have led people to seek alternatives to XML.

In addition, DTDs and entities are an interoperability headache because many XML parsers chose not to implement that part of the spec,

In his Turing award lecture (1980), Tony Hoare wrote:

When any new language design project is nearing completion, 

there is always a mad rush to get new features added before 

standardization. The rush is mad indeed, because it leads into 

a trap from which there is no escape. A feature which is omitted 

can always be added later, when its design and its implications 

are well understood. A feature which is included before it is fully 

understood can never be removed later.

   

There's a lot of truth in this, but with XML we've learned that "adding features later" only works if all the popular implementations get updated; and there's no guarantee that will happen.

As regards the whitespace issue, I suspect the problem is that the SGML and XML designers never really imagined how popular XML would become for pure data interchange applications, where it's natural to assume that whitespace (as a sibling of an element node) is insignificant, which in turn means that tools reformatting XML by adding indentation tend to assume that whitespace can be freely added and removed.

Michael Kay

Saxonica