How to avoid using a microsyntax in an attribute value?

[Roger L Costello <costello@mitre.org>]

Hi Folks,

I am creating a new language that will sit on top of the XML Schema language. That is, I am creating a set of attributes that will be inserted as foreign attributes into XML Schemas. The foreign attributes will be placed on element declarations. The foreign attributes are bound to the XYZ namespace:

xmlns:f="XYZ"

<xs:element name="dialog" type="xs:string" f:name="value" />

I want to create an attribute (or perhaps several attributes) that has this meaning:

	If the XML element in the instance
 	document contains the string ____, 
  	then replace that string with ____.

For example, consider this <dialog> element:

	<dialog>That is a large mountain</dialog>

I want to substitute large with small. 

Here is my initial thinking on how to express that:

<xs:element name="dialog" type="xs:string" f:substitute-A-with-B="A=large;B=small" />

You can see that I named the attribute "substitute-A-with-B" and its value is an encoding of the thing to be substituted (large) and the thing that is to replace it (small). 

Eek! 

I've created a microsyntax within the XML syntax.

I remember, long ago, Michael Kay advising people to avoid creating microsyntaxes.

That said, I rather dislike the idea of using two attributes to express substitution.

Is it possible to express substitution with one just attribute, without using a microsyntax?

What do you recommend?

/Roger