Re: [xml-dev] Your XML document is a programming language

[Michael Kay <mike@saxonica.com>]

On 9 Sep 2013, at 12:59, Costello, Roger L. wrote:

> Hi Folks,
> 
> This is a programming language:
> 
> <Book>
>    <Title>____</Title>
>    <Author>____</Author>
> </Book>
> 
> Don't let the angle brackets and element names deceive you, it is a programming language.
> 
> When I execute this program
> 
> <Book>
>    <Title>Six Great Ideas</Title>
>    <Author>Mortimer Adler</Author>
> </Book>
> 

Hang on, first you tell us that this snippet is a programming language, then you tell us it's a program.

Well, it's easy to see how it is a program. "Beam me up, Scotty" is a program if someone designs a programming language that includes this as one of its permitted constructions, and if the language defines semantics for this sentence. For any string of characters, you can design a programming language in which that string of characters is a program. So you can certainly design a programming language in which your <Book>..</Book> sample is a program. It only becomes an interesting programming language if it is suitable for writing a sufficiently general class of programs, and that's something you have yet to demonstrate.

Michael Kay
Saxonica