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Re: minor whine about documentation arrows

From: Antoine Isaac <aisaac@few.vu.nl>
Date: Sun, 26 May 2013 16:39:59 +0200
Message-ID: <51A21EBF.70902@few.vu.nl>
To: <public-openannotation@w3.org>

This actually relates to recommendations I had made a long time ago for simplifying the conventions. Not all had been followed then, but of course I'm happy that someone's giving a try at it again :-)

+1 for not having any graphical distinction between the object vs. datatype properties
+1 for the UML stuff. In fact I believe that it's not really needed to have a different form of arrow for the rdf:type one. There's already the label...


> Straight vs Curved: Agreed. It doesn't make a significant difference most of the time, and the resource vs literal is sufficient to easily visually distinguish.
> Open Arrows: Right, it's not class related but not instantiation. I'm happy to remove the UML comment. (And as a non substantive change, will do so now)
> Rob
> On Fri, May 24, 2013 at 3:26 PM, Bob Morris <morris.bob@gmail.com <mailto:morris.bob@gmail.com>> wrote:
>     OK, I understand that the graphical conventions [1] in the Feb 2013
>     spec are purely informative, and about the doc, not the model. But I
>     have come to decide that in publications it would be helpful to stay
>     as close to the graphics of the spec doc as feasible. In attempting to
>     do so, I have---so far-- one minor whine and one whimper.
>     Whine: I see no powerful reason to distinguish object predicates'
>     arrows from datatype predicates' arrows by whether they are straight
>     or curved. That distinction should be guided by the layout
>     constraints in the diagram. For both cases, it is easy to find
>     oneself forced into graphical ugliness by sticking to the convention.
>     Among the consequences are wasteful extra white space needed when
>     straight arrows are "required" and silly trivial curves when curved
>     ones are "required". By "required" I only mean, "attempting to follow
>     the documentation conventions." Besides all that, the two types are
>     already distinguished by the shape of their targets---ellipses for
>     objects, lozenges for literals. So it would be nice if the
>     documentation were simply silent on the matter of curves or straight
>     arrows. It wouldn't even require changing the pictures.
>     Whimper: It's a stretch to say "Class instantiation (rdf:type) is
>     depicted as a straight black line with white arrow head, following
>     UML." Most (all?) UML systems produce diagrams in which the
>     equivalent of rdf:type is denoted with ":" in the label of a box
>     depicting the object and its properties. There are no arrows for this
>     particular UML association between instances and classes. Other
>     associations between any UML objects are denoted with solid lines,
>     and, if those associations are directional, with open arrowheads.
>     Open arrows are generally (always?) reserved for the "generalizes"
>     association, useful in specifying a class hierarchy. I like the
>     triangular headed arrow convention for rdf:type, because it's an easy
>     to find graphical signpost that let's you ignore the predicate name
>     when it doesn't matter. But crediting it to UML makes me more, not
>     less, confused, especially in the face of other UML reserved words,
>     like "association" that are also used differently in UML. I would
>     remove "following UML" from [1].
>     Bob Morris
>     [1] http://www.openannotation.org/spec/core/index.html#Examples
>     --
>     Robert A. Morris
>     Emeritus Professor of Computer Science
>     UMASS-Boston
>     100 Morrissey Blvd
>     Boston, MA 02125-3390
>     IT Staff
>     Filtered Push Project
>     Harvard University Herbaria
>     Harvard University
>     email: morris.bob@gmail.com <mailto:morris.bob@gmail.com>
>     web: http://efg.cs.umb.edu/
>     web: http://wiki.filteredpush.org
>     http://www.cs.umb.edu/~ram
>     ===
>     The content of this communication is made entirely on my
>     own behalf and in no way should be deemed to express
>     official positions of The University of Massachusetts at Boston or
>     Harvard University.
Received on Sunday, 26 May 2013 14:40:36 UTC

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