What exactly is prohibited by the constraint of RELAX NG?

[Kohsuke KAWAGUCHI <kohsuke.kawaguchi@eng.sun.com>]

Of three decision made today (att/elem in att, att/elem in list,
duplicate attribute), the "duplicate attribute" looks like the most
complex one.

So here is my attempt to summarize it:

restrictions:

#1  For every group <group> p1 p2 </group> and <interleave> p1 p2
    </interleave>, it is an error that p1 and p2 contains attribute
    patterns whose name may collide.

#2  For every <oneOrMore> p1 </oneOrMore>, if p1 contains attribute
    patterns, then no <group/> or <interleave/> is allowed between that
    attribute and <oneOrMore/>

Both restrictions apply after the normalization.



This algorithm detects the first condition:

NameClass possibleNames( Pattern p ) {
    switch( p ) {
    case <group> p1 p2 </group>:
    case <interleave> p1 p2 </interleave>:
        nc1 = possibleNames(p1)
        nc2 = possibleNames(p2)
        if( intersection of nc1 and nc2 is non-empty )
            reject this pattern.
        return <choice> nc1 nc2 </choice>;
        
    case <choice> p1 p2 </choice>:
        return <choice> possibleNames(p1) possibleNames(p2) </choice>;
        
    case <attribute> nc p </attribute>:
        return nc;
        
    case <oneOrMore> p </oneOrMore>:
        return possibleNames(p);
    
    case <element> nc p </element>:
    case <empty/>:
    case <notAllowed/>:
    case <data/>:
    case <value/>:
        return <not><anyName/></not>;
}

This algorithm detects the 2nd condition by invoking "check(p,false)"

void check( Pattern p ) {
    switch( p ) {
    case <group> p1 p2 </group>:
    case <interleave> p1 p2 </interleave>:
    case <choice> p1 p2 </choice>:
        check(p1,inOneOrMore);
        check(p2,inOneOrMore);
        
    case <oneOrMore> p </oneOrMore>:
        if(haveGroupedAttribute(p))
            reject this pattern;
    
    case <attribute> nc p </attribute>:
    case <element> nc p </element>:
    case <empty/>:
    case <notAllowed/>:
    case <data/>:
    case <value/>:
        return;
}

boolean haveGroupedAttribute( Pattern p ) {
    switch( p ) {
    case <group> p1 p2 </group>:
    case <interleave> p1 p2 </interleave>:
        return haveAttribute(p1)||haveAttribute(p2);
    
    case <choice> p1 p2 </choice>:
        return haveGroupedAttribute(p1)||haveGroupedAttribute(p2);
        
    case <oneOrMore> p </oneOrMore>:
        return haveGroupedAttribute(p);
    
    case <attribute> nc p </attribute>:
    case <element> nc p </element>:
    case <empty/>:
    case <notAllowed/>:
    case <data/>:
    case <value/>:
        return false;
}

boolean haveAttribute( Pattern p ) {
    switch( p ) {
    case <group> p1 p2 </group>:
    case <interleave> p1 p2 </interleave>:
    case <choice> p1 p2 </choice>:
        return haveAttribute(p1)||haveAttribute(p2);
    
    case <oneOrMore> p </oneOrMore>:
        return haveAttribute(p);
    
    case <attribute> nc p </attribute>:
        return true;
    
    case <element> nc p </element>:
    case <empty/>:
    case <notAllowed/>:
    case <data/>:
    case <value/>:
        return false;
}



--
Kohsuke KAWAGUCHI                          +1 650 786 0721
Sun Microsystems                   kohsuke.kawaguchi@sun.com