Re: [GTFS-realtime] Re: proposed addition to spec: TripDescriptor.direction_id

[Brian Ferris]

Since the style these days is leaning towards fully defining experimental fields in gtfs-realtime.proto, I'd like to go ahead and explicitly add the definition for TripDescriptor.direction_id to the public proto.  Recall that we already reserved the field # and I already know of a few feed producers and consumers who are using it, so this seems like a natural next step.

Unless, I here any objections, I will add this field (marked as experimental) in the next day or two.

On Mon Feb 10 2014 at 6:35:29 AM Brian Ferris <bdfe...@google.com> wrote:

Ok, as there are no objections raised, I'm going to reserve field 6 of the GTFS-realtime TripDescriptor message for the direction_id field as proposed.  Note that this does NOT mean that the proposal has officially been adopted to the spec. Rather it means that GTFS-realtime producers and consumers will be using the specified field for evaluating this proposal for official adoption in the spec.

Thanks,

Brian

On Fri, Jan 31, 2014 at 11:14 AM, Brian Ferris <bdfe...@google.com> wrote:

I wanted to revive this proposal.  Since no one objected strongly when I made the suggestion two months ago, I'd like to formalize this proposal:

Let's reserve field #6 in TripDescriptor for this new field:

// The direction_id from the GTFS feed trips.txt file, indicating the direction of travel for this trip.

optional uint32 direction_id = 6;

Assuming I hear no objections, I will probably go ahead and reserve the field, as well as adding support in the OBA GTFS-realtime library.

Thoughts?

On Tue, Nov 26, 2013 at 6:17 PM, Brian Ferris <bdfe...@google.com> wrote:

I wanted to bump this thread again.  It seems like the field type is still the main issue at this point.  Any chance we can come to some consensus?  I'll admit that I still prefer "uint32".  Is there anyone who feels strongly enough that this is the wrong choice that'd they'd oppose adoption?

On Tue, Nov 19, 2013 at 9:17 PM, Michael Smith <msmith...@gmail.com> wrote:

Given that I think consistency is a good thing, would it be possible to also revisit the GTFS spec to see if both GTFS-realtime and GTFS can both be integers without breaking existing applications?

Mike

On Tue, Nov 19, 2013 at 11:58 AM, Barker, David <DBa...@mbta.com> wrote:

Valid reasoning. I certainly wouldn't object to it being an integer. 

-Dave (via mobile device)

Dave Barker, Manager of Operations Technology

On Nov 19, 2013, at 2:54 PM, "Brian Ferris" <bdfe...@google.com> wrote:

I think if there is any chance we'd want GTFS trips.txt direction_id to allow more than two values at some point in the future (conceivable), then that's a good reason to make GTFS-realtime direction_id a uint32, not a bool.  If we pick bool now, it becomes extremely difficult to change the type in the future.  Plus, direction_id just doesn't feel like a bool to me, as it's almost always communicated as 0 or 1 in GTFS, not as "true" or "false".

On Tue, Nov 19, 2013 at 11:50 AM, Michael Smith <msmith...@gmail.com> wrote:

It is certainly desirable for there to be just two directions. But I have seen so many complicated configurations that I'm sure some, though a very small number, could need more.  Still, for consistency, I think it should indeed be limited to a Boolean. 

Mike

On Nov 19, 2013, at 7:33 AM, "Dave Barker, MBTA" <dba...@mbta.com> wrote:

Agreed! When known this is a highly valuable piece of data. 

Regarding bool vs. uint32, I would tend towards bool, since direction_id is described as a "binary value" in the GTFS spec.

-Dave Barker, MBTA

On Monday, November 18, 2013 8:17:40 PM UTC-5, ethan.arutunian wrote:

Based on the discussion around Metro North's real-time feed, I would like to formally propose the addition of the "direction_id" field to the TripDescriptor definition:

Field Name: direction_id
Type: uint32? bool? (open to suggestions here)
Cardinality: optional
Description: The direction_id from the GTFS that this selector refers to.
The direction_id field contains a binary value that indicates the direction of travel for a trip. Use this field to distinguish between bi-directional trips with the same route_id. This field is not used in routing; it provides a way to separate trips by direction when publishing time tables.

• 0 - travel in one direction (e.g. outbound travel)
• 1 - travel in the opposite direction (e.g. inbound travel)

The proposed initial GTFS-realtime producer is Metro North Railroad (to be added to their real-time feed).
The proposed initial consumer is Roadify (to test the change).

This is an official request for comments on the proposed change.

Thanks for your consideration!

-ethan

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[Brian Ferris]

Ok, the new field has been added, marked as experimental.  All language bindings have been updated as well.