Implement SIRI Lite

[leonardehrenfried]

Goal / high level use-case

Some SIRI data providers implement only SIRI Lite, which means that rather than using the request/response pattern, the client sends a GET request downloading all of the data.

Describe the solution you'd like
OTP should support this workflow natively.

Describe alternatives you've considered

A proxy.

cc @rcavaliere @fahrplaner

[leonardehrenfried]

@abyrd says the following:

http://www.normes-donnees-tc.org/wp-content/uploads/2018/10/Proposition-Profil-SIRI-Lite-initial-v1-3.pdf
See section 2.1.3. This profile was a back-formation from practices at the NY MTA and OpenPlans described at https://bustime.mta.info/wiki/Developers/SIRIIntro

[abyrd]

At today's meeting @leonardehrenfried mentioned that no one seemed to know for certain whether SIRI Lite was supposed to return JSON or XML.

My understanding is that SIRI Lite was proposed as an official aspect of SIRI by Christophe Duquesne in this document: http://www.normes-donnees-tc.org/wp-content/uploads/2018/10/Proposition-Profil-SIRI-Lite-initial-v1-3.pdf
It states that SIRI Lite returns either JSON or XML depending on the situation. See section 2.1.3 for a description of how XML is mapped to JSON.

My understanding is that SIRI Lite was a formalization of practices seen in the wild at the NY MTA and OpenPlans. This page describes the system that introduced the practices that were formalized as SIRI Lite: https://bustime.mta.info/wiki/Developers/SIRIIntro

It says: "While the SIRI standard specifies XML as an interchange format, it incurs a substantial penalty in data-transfer and processing requirements. In contrast, JSON (Javascript Object Notation) is a lightweight data-interchange format. Human-readable, lightweight, and easy to parse, JSON offers an alternative. Thus, MTA Bus Time provides both XML and JSON versions of its API."

This page asserts that the MTA contributed directly to the normalization (standardization) process:
http://www.normes-donnees-tc.org/format-dechange/donnees-temps-reel/

[abyrd]

I updated the title and a comment to say "SIRI Lite" instead of "Light". All sources I could find spell it "Lite". The motivation is that I was baffled when searching for this ticket using the word "Lite" and couldn't find it :)

[leonardehrenfried]

I reject this Americanism :)