Link Contracts revised

["Giovanni Bartolomeo" <giovanni.bartolomeo@uniroma2.it>]

Hello,

I was revising link contracts and I've noted the following two issues:

We have this example:

=drummond+friend$contract$sig
	$has
		=web*markus	<-- Drummond adds Markus to this contract -->

Thus a new subject is created:

=drummond+friend$contract$sig=web*markus

ISSUE#1: since $has is left associative (+a+b+c <==> ((+a/+b)/+c)),  
see mail "Key implications of new metagraph $has definition" (May 4,  
2009) this statement is parsed as =web was part of the composite  
subject =drummond+friend$contract$sig=web, and not part of =web*markus.
To solve this, my proposal is to use xref, as follow:

=drummond+friend$contract$sig(=web*markus)

ISSUE#2: we have now the following entailment (+x+y==>+x+y/$is$a/+y):

=drummond+friend$contract$sig(=web*markus)
	$is$a
		=web*markus

this sounds a bit odd. My proposal is to change the original statement  
as follow

=drummond+friend$contract
	$has
		=web*markus$sig	<-- Drummond adds Markus to this contract -->

This way we have the new composite subject  
=drummond+friend$contract(=web*markus$sig) which correctly entails

=drummond+friend$contract(=web*markus$sig)
	$is$a
		=web*markus$sig

There would be more to say about the relationship btw $contract$sig  
and =drummond+friend$contract(=web*markus$sig), OO people (like  
myself) could see inheritance and polimorphism applied here, but for  
the moment just stop here, waiting for your comments.

Kind Regards,
Giovanni

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