Rules for deciding when behavior should be specified?

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

Hi Folks,

I am interested in putting together a list of "rules" for when behavior
should be specified.  I seek your help in completing this list.  Below
I have made a start.

To state the issue more precisely: suppose you are writing a
specification for a new XML vocabulary.  In your specification, for
each element and attribute you define:

   - its syntax
   - its semantics

Should behavior also be specified? 

Should you provide information about how an application should behave
upon encountering an element or attribute from the XML vocabulary?  

What are the rules for determining whether behavior should be
specified?  

Let's list those rules!

RULES FOR DECIDING WHEN BEHAVIOR SHOULD BE SPECIFIED

A specification should provide behavior information when:
 
1. There is one primary application to which the XML vocabulary is
targeted.

   Example: the XSLT vocabulary is targeted primarily to
   applications called XSLT processors.  Other applications,
   of course, can process an instance document that uses
   the XSLT vocabulary.  But the vocabulary was designed
   primarily for XSLT processor applications.

2. You want to be able to "certify for compliance" applications that
process the XML vocabulary.

   Example: I want to only use XSLT processors that have
   been certified to comply with the behavior specified in
   the XSLT specification.

3. There will be recipients (of instance documents that uses your XML
vocabulary) who will be unfamiliar with the data and the domain.
Providing those recipients with just the data is insufficient.  They
need help knowing what to do with the data.

   Example: From Carl Sagan's movie "Contact": Earth received radio 
   signals from a highly advanced civilization from a distant 
   galaxy.  Embedded within the signals are both data and 
   instructions for using the data (it described how to build 
   a device to transport humans at faster-than-light, as I recall).
   Without a specification of the behavior, the "Contact" data 
   would have been unfathomable to the Earthlings.

For what other occasions would it be important for the specification of
an XML vocabulary to specify behavior?

Thanks!

/Roger