Multi-Device Web apps

Outline

• W3C & the Web platform
• Multi-device Web apps?
• Communication channels
• Multi-device session bootstrapping
• Cross-device app state
• Content adaptation and synchronization

W3C

• Standards setting body for the Web
• 400 Members, with most key players in ICT
• 70+ staff, mostly technical
• Founded by Web inventor, Tim Berners-Lee
• Key foundational principles:
  1. Interoperability
  2. Openness
  3. Royalty-free patent policy

w3.org/mob

Users have more than one device

Seamless integration of users devices leads to a better UX

Challenges

• Different constraints in screen sizes, CPU, connectivity, user input
• Incompatible development environments
• Difficulty to enroll devices
• Keeping it synchronized

Based on Web technologies

Web technologies are available on any device

Research on multi-device apps

Building blocks

• Communication channels
• Device enrollment
• Cross-device app state
• Content adaptation (2nd talk)
• Content synchronization across devices (3rd talk)

HTTP (long) polling

• Around since the beginning
• Hack to emulate dual-way communication
• Not very efficient
• More a fallback mechanism

WebSockets

• Dual-way communication channel
• Now supported by all Web browsers (but not HBBTV 1.5)
• Communication goes through a server

WebRTC

• Peer-to-peer communication channel
• Allows to stream audio, video and data in real-time
• Under development but already available in Chrome, Firefox
• P2P mode hard to scale to many devices

Problem definition

Starting point

An app running on a first device wants to create a multi-device experience with a second device.

Final point

The two devices are able to exchange messages over some communication channel

Presentation

Source: "Enabling second display use cases on the web" — Dominik Röttsches, Anssi Kostiainen (Intel Corporation), Fourth W3C Web and TV Workshop

Media "flinging"

Source: "Enabling second display use cases on the web" — Dominik Röttsches, Anssi Kostiainen (Intel Corporation), Fourth W3C Web and TV Workshop

Gaming

Source: "Enabling second display use cases on the web" — Dominik Röttsches, Anssi Kostiainen (Intel Corporation), Fourth W3C Web and TV Workshop

Network Service Discovery

• An API to discover and communicate with services discovered on the current network
• Lots of enthusiasm initially
• CORS support required to address security & privacy issues
• No support for legacy devices as a consequence
• Uncertain future

From devices to screens

• The concept of devices is too broad
• Screens are more user- and scenario-focused
• Restricts the scope of potential issues
• Allows to abstract away the attachment method

Attachment methods

The Presentation API

• Mechanism to request display of Web content on a second screen
• Browser used as mediator
• Discovery logic not exposed to Web apps
• Abstracts away the screen's attachment method
• Not necessarily restricted to the local network
• Defines a “session” for multi-screen apps

Other ways to bootstrap sessions

• Push notifications (based on Service Worker)
• Bluetooth, e.g. Google's Physical Web
• QR codes, NFC
• Network Web Sockets?

Shared state

• Clients have access to the same data model
• Clients can query and update the data
• Clients are notified when data is changed
• No explicit message passing

Asynchronous state

• All updates will propagate over time
• Code needs to listen to change events

Content adaptation

How to author multi-device Web apps that adapt themselves to the capabilities of devices that are available, best practices and possible enhancements to standards to ease the life of developers.

Content synchronization

How to synchronize content across heterogeneous devices, including animations, transitions, and media.

Thanks!

• Slides: http://www.w3.org/2015/Talks/dhm-multidevice-w3ctrack/
• Twitter: @dontcallmedom
• Email: dom@w3.org

This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement 610404