Issue 15790: OCL 2.2 Missing definition of navigation (ocl2-rtf)
Source: Model Driven Solutions (Dr. Edward Willink, ed(at)willink.me.uk)
Nature: Uncategorized Issue
Severity: 
Summary: Dot and arrow navigation have implied definitions in the non-normative clause 7, but nothing in the normative clauses.


Implicit collect is missing from clause 9, save for the throwaway final sentence "The mapping
is not formally defined in this document but should be obvious."


This mapping is far from obvious; if it was obvious it would be easy to define.


In particular it is important to define that a static syntax determination is made to ensure that:


anObject . feature => object navigation
anObject -> feature => implicit collection (of anObject's static ordering/uniqueness) containing a non-null anObject
aCollection -> feature (or iterator) => collection navigation
aCollection . feature (or iterator) => implicit collect = aCollection -> collect(feature or iterator)
(implicit source object implicit .) feature => object navigation
(implicit source collection implicit ->) feature (or iterator) => collection navigation


with the object/collection discrimination performed statically, so that the navigation
algorithm is statically determinate; only the dynamic dispatch on self is subject to
dynamic determination.


The conformance of a collection to OclAny must never used to allow object navigation on a collection. This avoids a syntax ambiguity for "aCollection . name" between implicit collect and object navigation of a collection feature, or between implicit collect and object navigation of an object feature.



Resolution: 
Revised Text: 
Actions taken:
October 31, 2010: received issue
Discussion: 

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Date: Sun, 31 Oct 2010 15:07:23 +0000
From: Ed Willink <ed@willink.me.uk>
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To: issues@omg.org
Subject: OCL 2.2 Missing definition of navigation


Hi


Dot and arrow navigation have implied definitions in the non-normative clause 7, but nothing in the normative clauses.


Implicit collect is missing from clause 9, save for the throwaway final sentence "The mapping
is not formally defined in this document but should be obvious."


This mapping is far from obvious; if it was obvious it would be easy to define.


In particular it is important to define that a static syntax determination is made to ensure that:


anObject . feature => object navigation
anObject -> feature => implicit collection (of anObject's static ordering/uniqueness) containing a non-null anObject
aCollection -> feature (or iterator) => collection navigation
aCollection . feature (or iterator) => implicit collect = aCollection -> collect(feature or iterator)
(implicit source object implicit .) feature => object navigation
(implicit source collection implicit ->) feature (or iterator) => collection navigation


with the object/collection discrimination performed statically, so that the navigation
algorithm is statically determinate; only the dynamic dispatch on self is subject to
dynamic determination.


The conformance of a collection to OclAny must never used to allow object navigation on a collection. This avoids a syntax ambiguity for "aCollection . name" between implicit collect and object navigation of a collection feature, or between implicit collect and object navigation of an object feature.


    Regards


        Ed Willink