Re: minor whine about documentation arrows

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> 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
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> email: morris.bob@gmail.com
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> ===
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