Fwd: Explanation of s-ramp query grammar problem

[Kurt T Stam <kstam@redhat.com>]

Hi Guys,

Eric works with me on S-RAMP and while implementing the Query API he noticed that our query grammar does not supports literals to be arguments in function calls. Would it make sense to update the grammer slightly?

Thx,

--Kurt

-------- Original Message --------

Subject:	Explanation of s-ramp query grammar problem
Date:	Tue, 17 Jul 2012 10:23:58 -0400
From:	Eric Wittmann <eric.wittmann@redhat.com>
To:	Kurt Stam <kstam@redhat.com>

Problem:

As defined, the S-RAMP query grammar does not allow literals to be 
arguments to function calls.


Relevant Grammar:

FunctionCall ::= FunctionName '(' ( Argument ( ',' Argument )* )? ')'
Argument ::= Expr
Expr ::= EqualityExpr
EqualityExpr ::= ForwardPropertyStep '=' PrimaryExpr
PrimaryExpr ::= Literal  |  Number  |  '$' PropertyQName

I condensed the grammar a bit (took out boolean _expression_ definitions 
and whatnot) to illustrate the point.  You can see that the only way to 
get to a PrimaryExpr is on the right-hand side of an EqualityExpr.


Example:

/s-ramp/xsd/XsdDocument[classifiedByAnyOf(., 'taste')]

The example above breaks down as an artifact set with a predicate where 
the predicate is a function call with two arguments.  The second 
argument is expected to be PrimaryExpr:

ArtifactSet [ FunctionCall ( RelationshipPath, PrimaryExpr ) ]

But the grammar states that an Argument must be an Expr, which does 
*not* allow it to be a simple PrimaryExpr.


Proposal:

Update the grammar, changing Argument to be defined as:

Argument ::= PrimaryExpr
           | Expr

This is the simplest grammar change that will support the example, but 
it is not the only one.