[furcas-discussion] Reference Re-Evaluation Algorithm

[Stephan Erb]

Hey everybody,

here the result of our last whiteboard session:

> Create a collect expression only consisting of lookupScope and referenceBy. (It does not contain ?, prefix or postfix).
> Register the IA on this expression
> Register the IA on the lookupScope expression
>
> If the IA triggers for one of these two registrations, then:
>
> 	Filter the affected elements. Only those may remain for which a TB is 
> 	documenting that the above triggered expression may be executed.
>	(See IAExpressionInvalidationChangeListener in the MOIN code base)
>
> 	For all remaining effected elements and their associated document nodes:
> 		
>		Determine if the given reference is bound. Probably this works by inspecting
>		the 'referrencedModelElements'. The context element at hand may be visible
>		in several textual views. If at least one of these documents that the reference is bound
>		then we consider this to be true. Views indicating otherwise are considered to be stale.
>
>		evaluate the lookupScope
>
>		If bound and the bound element is still in the current lookup scope then:
>			
>			Update all corresponding token values. The tokens are set to
>			the evaluation result of referenceBy on the bound element.
>			Prefix and postfix are substracted. If prefix and postfix do not match
>			the given name then the bound reference will be unset.
> 
>		else if bound but the bound element is no longer in the lookup scope then:
>			
>			Retrieve the name of the previously bound element (overruling the
<			respective token value). Use this name to perform a fresh lookup
>			using lookupScope, referenceBy, prefix and postfix. Set the reference
>			based on the result or break it, if nothing was found.
>		
>		else if not bound:
>
>			Perform a fresh lookup. The lookup is performed with the current token value
>			at hand, using lookupScope, referenceBy, prefix and postfix. Set the reference
>			based on the result or break it, if nothing was found.
>

Tasks:

      * Axel will implement a ModelUpdater using to the given algorithm.
      * Sebastian will write several test cases:	
              * Tests covering all branches of the algorithm.
              * A testcase where the model is constructed in memory. We
                will use it to test the algorithm if no TB model is
                available.
              * A set of testcases operating on the text level:
                search/replace in the TB model with a subsequent call of
                the incremental parser.


Happy Hacking!
Stephan

PS: Thomas, we might need your help with all this textblocks magic (e.g.
find out if a reference is still bound). Expect some questions on the
mailing list rather soon :-)