| Re: Branches and connections - a neverending story [message #81 is a reply to message #79] |
Fri, 11 June 2004 15:24   |
Matthias Hengartner
Messages: 57
Registered: August 2003
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Member |
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Hello,
Thank you for your suggestions.
Some weeks ago, I discussed with Ulrich Linder the topics I mentioned in the
newsgroup in early april.
We decided to remove the <singleCrossOver>-element, because it would raise
unnecessary work for importing applications. So <switch> will be the only
child element of <connections> for the present. Of course we could discuss
about the sense and the naming of this <connections>-container.
Additionally we developed the idea of having another optional track
attribute like "trackType" or similar, where we can specify what kind of
track it is (e.g. "mainTrack", "crossOverTrack" or "holdingTrack").
Here a simple example (I removed attributes which are not relevant for this
topic and added the attribute "trackType" to show roughly what we mean).
-------------------------- Track 1
\
\
-------------------------- Track 2
<track trackID="Track1" trackType="mainTrack">
<trackTopology>
<trackBegin>
<bufferStop connectionID="15" pos="0"/>
</trackBegin>
<trackEnd>
<bufferStop connectionID="16" pos="10"/>
</trackEnd>
<connections>
<switch connectionID="20" pos="4.98000" dir="up">
<branchConnection branchIDRef="25"/>
</switch>
</connections>
</trackTopology>
</track>
<track trackID="Track2" trackType="mainTrack">
<trackTopology>
<trackBegin>
<bufferStop connectionID="18" pos="0"/>
</trackBegin>
<trackEnd>
<bufferStop connectionID="19" pos="10"/>
</trackEnd>
<connections>
<switch connectionID="21" pos="5.00000" dir="down">
<branchConnection branchIDRef="26"/>
</switch>
</connections>
</trackTopology>
</track>
<track trackID="Track3" trackType="crossOverTrack">
<trackTopology>
<trackBegin>
<simpleConnection connectionID="25" pos="0">
<branchConnection branchIDRef="20"/>
</simpleConnection>
</trackBegin>
<trackEnd>
<simpleConnection connectionID="26" pos="0.025">
<branchConnection branchIDRef="21"/>
</simpleConnection>
</trackEnd>
</trackTopology>
</track>
As you can see, we have an additional third track for the crossover.
There is still some redundancy, but nevertheless, the consistency is better
for the following reasons:
- if there is a switch, we have a <switch> element
- each track has a beginning and an end which is either a <bufferStop> or a
<simpleConnection>
- a <simpleConnection> can have a branchConnection, which refers either to
another <simpleConnection> of another track (to simply connect 2 tracks) or
to a <switch> of another track (which of course means that this track begins
as a branch of the other track)
So parts of your suggestions are integrated in the current development of
the scheme. Your idea of simplifying crossovers with the attributes
"fromElemID" and "toElemID" is good, but as I already mentioned above, we
decided not to have a "special treatment" for crossover tracks but to have
an separate track.
Do you agree with this idea?
Have a nice weekend,
Matthias
----- Original Message -----
From: "Volker Knollmann" <volkerknollmann(at)dlrde>
Newsgroups: xml.line
Sent: Friday, June 11, 2004 11:05 AM
Subject: Branches and connections - a neverending story
> Hello,
>
> I just was preparing some RailML-example-code and had a close look at
> the current schema (0.94_18) when I came across some difficulties
> related to switches, branches and connection. The problems refer to
> Matthias' posting from April 13.
>
> Like Matthias, I don't understand the neccesarity for <singleCrossOver>.
> In fact, it is a switch, so why don't we use the <switch>-element?
> Additionally I found that using the current syntax, we always have to
> include two <branchConnection>-elements with the same contents (one in
> each <track> of the branch). This creates unneccessary redundancy.
>
> My suggestion to reduce the complexity of branches and connections is:
> * skip <singleCrossOver>
> * use <switch> for every kind of branch
> * rename <connections> to <switches> and make it an ordinary container
> element
> * make <branchConnection> a child of <tracks> to include it only once
> per branch. Introduce an appropriate container element.
>
> I think, the last point makes sense. Since a branch connects TWO tracks,
> it should NOT be a child of a track. It should be a sibling of <track>.
>
> Here's a very simple example (ASCII-art):
>
> ------------------------------ Track 1 of Line A
> \ /
> \ /
> ------------------------------ Track 2 of Line A
>
> <line lineID="A">
> <tracks>
> <track trackID="1" length="42.000">
> <trackTopology>
> <switches>
> <switch connectionID="SW1" pos="1.000">
> <switch connectionID="SW2" pos="1.500">
> </switches>
> </trackTopology>
> </track>
> <track trackID="2" length="42.000">
> <trackTopology>
> <switches>
> <switch connectionID="SW3" pos="1.060">
> <switch connectionID="SW4" pos="1.440">
> </switches>
> </trackTopology>
> </track>
> <branchConnections>
> <branchConnection fromElemID="SW1" toElemID="SW3"
> branchDist="0.065" />
> <branchConnection fromElemID="SW2" toElemID="SW4"
> branchDist="0.065" />
> </branchConnections>
> </tracks>
> </line>
>
> I skipped many attributes which are required "in real life"; my
> intention was to show the idea and the structure.
> Using the attribute-names "fromElemID" and "toElemID", the branch has an
> implicit direction (like a vector), so the usage of the "dir"-attribute
> would be possible.
>
>
> So what do think? I'm looking forward to your suggestions and comments!
>
> Best regards from Braunschweig,
> Volker Knollmann
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