Inheritance/defaulting of attributes

Tim Bray tbray at
Wed Oct 8 02:51:48 BST 1997

At 05:25 PM 07/10/97 -0700, Andrew Layman wrote:
>We are seeing that on this list also.  Clearly inheritance is going to
>be difficult to work out.

I'm really glad Andrew posted that.  I have heard too many people, not
just on this list, saying things like

                  |-parameter entities   |
                  |-architectural forms  |
"Well, of course-<--DTDs                  >--support O-O inheritence."
                  |-HyTime               |
                  |-Hypertext in general |
                  |-Document schemas     |

After years of struggle, we've got a pretty good handle on how to
do some useful kinds of inheritence with reasonable safety, in the
software module world.

Documents are different.  To start with, it's far from clear to me
that the term "inheritance," standing by itself, has a useful
semantic in the context of documents.  

This has a practical consequence.  We should, in future, struggle
for greater precision; for example, however it is clear that 
however LOCATOR attributes depend on those in the parent EXTENDED 
linking element, it ain't inheritance in the O-O style. -Tim

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