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Mobile App Design Considerations

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barbeau edited this page Sep 28, 2012 · 25 revisions

Interesting in creating a mobile app that uses OneBusAway for real-time transit data? You're in the right place.

Before you start your own app, check out the existing open-source OneBusAway (OBA) apps to get ideas, and make sure you're not duplicating features that already exist:

You might even want to contact the developers and see if you can pitch in to add new features to the existing apps.

The Anatomy of OBA-related Transit APIs

Like many open-source projects, OneBusAway is changing quickly. Check out the [OBA RESTful API Roadmap] (https://github.com/OneBusAway/onebusaway-application-modules/wiki/RESTful-API-Roadmap) for a list of APIs that are currently supported in OneBusAway, as well as the plan for what APIs will be supported in the future.

Also check out the SIRI Element to UI Mappings for a description of the SIRI element fields and how they should be shown to transit riders.

Design Considerations

Overview

In general, we suggest using the JSON interfaces for OneBusAway. JSON is a more compact representation of data than XML, and therefore more efficient. This means less data sent over the wireless network and better battery life for a mobile phone.

Format of SIRI responses

To conform with the SIRI standard, XML and JSON element labels are in PascalCase (i.e., not camelCase, where the first letter is lower-case).

XML:

<RecordedAtTime>2012-09-12T09:27:52.867-04:00</RecordedAtTime>

JSON:

"RecordedAtTime":"2012-08-21T12:07:21.485-04:00"

Java-based JSON and XML data binding parsers such as Jackson can typically be configured to handle PascalCase, even though they typically expect camelCase, since the Java POJOs used in data binding typically define fields in camelCase.

However this presents a problem for certain attributes. Consider the following XML:

<Summary xml:lang="EN">b/d 1:00pm until f/n. local and express buses run w/delays & detours. POTUS visit in MANH. Allow additional travel time Details at www.mta.info</Summary>

The xml:lang attribute must remain lower-case because of XML language attribute definition defined by W3C. Therefore, if you configure your JSON or XML parser to use PascalCase for elements, be aware that you will need to configure it to make an exception for attributes such as xml:lang.

TODO - add how to handle xml:lang in Jackson, also add this to SiriRestClient pages.

Platform-specific information

Below are some pointers for developing OneBusAway apps on various mobile platforms.

Android
Real-time mobile SIRI API - JSON and XML parsing

We've created Siri Rest Client, an open-source reference implementation Android app that shows how to access and parse SIRI data in both JSON and XML format. Feel free to use this project as a basis for your app, as the source code is licensed under Apache 2.0.

We've developed several tutorials based on what we've learned implementing the SiriRestClient, especially in the area of JSON and XML parsing on Android:

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