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  1. OMG Issue

MOFM2T11 — File unique id is not useable

  • Key: MOFM2T11-5
  • Legacy Issue Number: 14434
  • Status: open  
  • Source: Obeo ( Laurent Goubet)
  • Summary:

    In section 7.3, the file block of the MOF model to text transformation language is detailed. This section introduces the "uniqId" attribute of the file blocks which is meant to allow a tool to find back a generated file even if the object from which it's been generated changed significantly since the last generation.

    Though this is a good thing in theory, such an ID cannot be implemented whatever the programming language chosen. Or rather, it cannot be implemented in a satisfying way. Let's assume we have this file block :
    [file ('c:/'.concat('.c'), false,]

    So a file "class.c" will be generated at the root of disk c. Now I change my module so that now, the file block resembles this :
    [file ('d:/generated/'.concat('.c'), false,]

    The class itself hasn't changed one bit; so both the file name (class.c) and its id ( remain constant. How can the tool find back that a file has already been generated for such an ID?

    The tool itself cannot keep a reference to all files it has generated along with their IDs and locations; the possibility that we're generating files under version control and that others can generate the same on their own machines forbids this. The solution would then be to save the file along with its ID, thus breaking the WYSIWYG assumption of the specification as unwanted information would show up in the generated file.

    And even like that, the tool would need to lookup throughout the whole file system of the target in order to try and find a file which ID is the same as what we need to generate. With the current computers, that could mean searching within terabytes of data in order to find a file that might not even exist in the first place, and that for each [file] block of a generation module.

    I believe this unique ID is a good idea in theory, yet seeing as this idea cannot be implemented as more than an idea, I think all references to an ID should be removed from 7.3 (description of the file block), 8.1 (metamodel), 8.1.17 (file block's attributes) and 8.2 (concrete syntax).

  • Reported: MOFM2T 1.0 — Mon, 28 Sep 2009 04:00 GMT
  • Updated: Fri, 6 Mar 2015 20:58 GMT