Re: Status of connectors for SVG2

Hello world,

David Dailey wrote:
> 
> Circa Thursday, July 10, 2014 3:38 PM
> 
> Juergen, Doug and Tav all wrote about connectors: current status [1,2], new ideas, lack of implementer buy-in.
> 
> I've always liked connectors (since I work a lot with graphs and we've had to develop our own xml format for storing them, as well as a zillion lines of JavaScript to create, edit, and interrogate them). Antireflexive binary relations (directed graphs) and antireflexive, symmetric binary relations (graphs) are intensely ubiquitous in that part of the world that is modeled by mathematics (some would say that's the whole world) and are sort of a lingua franca of modern (post 1970's) computing theory and discrete math. Their relevance to web pages has always seemed so obvious that I've had a hard time justifying them to nonbelievers. Self-evidence is sometimes its own worst enemy.

Yeah, graphs are a very weird thing - nobody wants to know about the 
theory, but everybody uses them in practice ...

> Anyhow, Juergen, since you've been working with these notions on presumably practical problems, perhaps it would be worth brainstorming with interested parties on a goodly collection of use cases. Perhaps once those with browser development teams, agenda, and priorities can see just how wonderful these constructs are, then the urgency for implementation will receive a boost. Just what sorts of problems will connectors solve that one would otherwise have to rely on script to do?

No, I am not "working with these notions in practice" (in general), I 
just had one usecase which I solved via an abstract XML syntax 
tranformed via XSLT to SVG, and then I came up with the idea to use it 
directly in SVG. Thus the research for connectors' state in SVG and my 
proposal.

My usecase is probably similar to OSM data: designing (in my case very 
simple and rather abstract) street maps, consisting of (mostly) linear 
segments connecting (mostly) crossings, some of the segments having 
additional attributes (footpaths, one-way, ... ). In that case, most of 
the refpoints are used more than once (end point of the former segment 
as well as start point of the next segment, crosspoints have more than 
just two uses). In my case, I do not model the segments, but I model the 
"streets" (a street with a name) and "special ways" (restrictions of 
parts of streets, i.e. footpaths, one-way-restrictions, ...), both as a 
sequence of refpoints with special attributes (names, restrictions). But 
instead of using a complex OSM syntax (and I would have to learn that, 
in advance), I made my simple syntax for a simple usecase ...

Other usecases of refpoints where I might have used that in advance 
might be annotations to graphical presentations - so I might have the 
annotation positioned at various places (for screen presentation at 
various screen sizes, for print-out, ...), and would need to change just 
a single coordinate pair for that instead of hundreds ...

Another possible usecase is highly dynamical: Once, my students 
implemented an actual map of the trams in Karlsruhe, and as trams are 
moving, mostly, and as you might have interconnections and annotations 
to them as well (and the other end of the interconnection might move in 
another way, and the annotation might not be moved at all), changing the 
coordinates of a single refpoint via a client-side script language would 
be a "nice thing to have" instead of going through all the coordinates 
of related points and adapt them via a client-side script language.

> (I know, now I'm sounding like an implementer rather than an advocate! Please slap me!)

I will not comment on that :-|

> [1] http://dev.w3.org/SVG/modules/connector/SVGConnector.html
> [2] http://www.w3.org/2013/09/12-svg-minutes.html 

Let me add two other references: The proposal of Tavmjong Bah [3], and 
my own simple example [4] with one possible syntax extension and a 
simple implementation of that via XSLT (with several limitations).

[3] http://tavmjong.free.fr/SVG/CONNECTORS/index.xhtml
[4] http://jroethig.de/geolog/connector.html

Regards,

Juergen Roethig

Received on Friday, 11 July 2014 09:04:56 UTC