Re: [dita] attribute specialization as foundation

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Subject: Re: [dita] attribute specialization as foundation




From: Dana Spradley <>
To: Erik Hennum <>
Date: Thu, 27 Apr 2006 08:58:18 -0700










I've just had time to skim it so far, but I can
already see that Erik's paper clearly and systematically outlines of
what attribute extension in general should look like - in addition to
many other valuable DITA extensions that would make the kind of
customization I've resigned myself to in any workable implementation
unnecessary.


But this just makes me wonder why I've been getting so much resistance
over what, unlike some of these extensions, should be a no brainer -
allowing DITA implementers to add arbitrary, implementation-specific
attributes to elements that will be ignored on generalization.


Erik recognizes the need for this:


Attribute addition
  Adding new properties to existing elements without losing
interoperability with others. Many problem domains have special
metadata that must be represented in the document instance. For
instance, warning notes for hardware might have an attribute that
identifies the regulation that motivates the warning. 



He also provides the use case and justification, along the same
object-oriented lines I've been arguing:



  The Object Oriented perspective and addition of properties to
discourse 
  In the Object Oriented approach, a specialized class inherits all
of the properties of the base class. These properties are often
accessed through extensible behaviors, but that nuance doesn't alter
the basic principle. The specialized class introduces variation by
adding new properties (in XML Schema parlance, through extension by
addition). 
  The following example shows the specialization of a class for
generic structural nodes to define a class for tree nodes. 
  
      
      General class
      Specialized class
    
     
      
        
        
        Node
    data: Object
    next: Node