Question regarding DR 09-0216

[MURATA Makoto (FAMILY Given)]

Doug,


> In the approach we've used for implementing this particular feature, 
> "can" is indeed correct.  The rationale behind that flexibility is that
> the user may be unaware that the custom XML markup exists, and they
> could make a change to a document that renders it invalid, by simply
> deleting a paragraph for example.  In that case, the user may not know
> what needs to be done to make their change in a schema-valid way, so
> they have no ability to correct the error if schema validation against
> the custom schema were required.  So we allow them to save the document
> anyway, preserving the user's intended content even if it is no longer
> consistent with the custom schema.

I still do not understand English, but here the word "can" appears to be used
for two purposes.  First, implementations are able to validate custom XML,
since schemas are available.  Second, implementations are allowed to but 
not required to validate custom XML.  "can" captures the first but not
the second.  Use "may but need not" for the second.

In the context of standardization, modal verbs (such as "can" and "may")
should be used with care just like instructions to computer programs, so
that non-native speakers are not confused.

The rest of this mail is extracted from Annex H of "ISO/IEC 
Directives, Part 2:  Rules for the structure and drafting of 
International Standards".

The verbal forms shown in Table H.3 shall be used to indicate a course
of action permissible within the limits of the document.

Table H.3 Permission 

-------------------------------------------------------
|Verbal form 
|      Equivalent expressions for use in exceptional cases  
|      (see  6.6.1.3) 
|
|-------------------------------------------------------
|may
|  is permitted 
|  is allowed 
|  is permissible 
|-------------------------------------------------------
|need not
|  it is not required that 
|  no … is required 
|-------------------------------------------------------
|Do not use "possible" or "impossible" in this context. 
|Do not use "can" instead of "may" in this context. 
|
|NOTE 1 "May" signifies permission expressed by the document, whereas
|"can" refers to the ability of a user of the document or to a
|possibility open to him/her.
|
|NOTE 2 The French verb "pouvoir" can indicate both permission and
|possibility.  For clarity, the use of other expressions is advisable
|if otherwise there is a risk of misunderstanding.
|-------------------------------------------------------
 
The verbal forms shown in Table H.4 shall be used for statements of
possibility and capability, whether material, physical or causal.


Table H.4  Possibility and capability 
|---------------------------------------------------------
|Verbal form
|   Equivalent expressions for use in exceptional cases (see 6.6.1.3) 
|
|---------------------------------------------------------
|can
|  be able to 
|  there is a possibility of 
|  it is possible to 
|---------------------------------------------------------
|cannot  be unable to 
|  there is no possibility of 
|  it is not possible to 
|---------------------------------------------------------
|NOTE     See Notes 1 and 2 to Table H.3.
|---------------------------------------------------------


Regards,

SC34/WG4 Convenor
MURATA Makoto (FAMILY Given)