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2.10 Migratory Interactive Applications
One of the main sources of frustration in current ubiquitous environments is that users need to restart their applications for each device change. In order to exploit the current technological offer there is a need for continuous access to interactive services across various devices. Migratory user interfaces can transfer among different devices (from ‘source’ devices to ‘target’ devices), so as to allow the users to continue their tasks. Various approaches to their implementation have been investigated (pixel replication, interactive applications, virtual machines, etc.). Several application domains can benefit from them such as shopping, online auctions, games, making reservations. They are characterised by the ability to preserve the state of the interactive part (which can include user input, focus elements, cookies, sessions, history bookmarks, etc).
An example of a solution supporting migratory user interfaces is DeepShot (Chang and Li, 2011). It identifies the application that the user is looking through the camera, recovers its state, and migrates it onto the mobile phone, with the information on the state encoded as URI. A video is available at
Various solutions for migration of interactive applications have been investigated within the EU OPEN project (http://saturno.isti.cnr.it:88/), which have been applied in various applications (games, emergency, social networks). Their detailed description is given in a book on Migratory Interactive Applications in Ubiquitous Environments
(http://www.springer.com/computer/information+systems+and+applications/book/978-0-85729-249-0). One such solutions has focused on an environment supporting migration of Web pages. This is obtained through a proxy server able to inject scripts that introduce the possibility to send the DOM of the page and its current state when migration is triggered through a migration client, which is a separate Web application able to communicate with the migration server and the applications.
There are some specific aspects that characterise usability in such environments. They are related to continuity, such as time required by the migration process from the trigger on source device to the user interface presentation on target device. The transition should be understandable by users, in the sense that users should be able to understand that a migration is taking place. The adaptation result should not make it difficult for the user to understand how to proceed. Another important aspect is predictability: users should be able to predict the target device, what UI parts are going to migrate, and where the user’s interactions results will appear after migration.
In order to make the migration environments more flexible we can introduce the possibility of partial migration in which the users interactively select the parts that they want to migrate to the target devices. This can be useful, for example, in desktop-to-mobile migration if users want to limit the parts to migrate in order to avoid overloading the limited screen of the target device. One issue with migration of Web applications is the state of JavaScripts. Indeed, if the state associated with JavaScript variables is not properly saved and restored, inconsistencies can be experienced: some variables no longer exist in the new version uploaded or some variables might hold incorrect values.
In any case, migratory interfaces can provide useful support also in multi-user environments. In Ghiani et al. (2012) an interesting scenario is discussed in which colleagues planning a business trip exploit it in order to push or pull web pages which contain useful information and data for their trip. A video illustrating this scenario is available at http://www.youtube.com/watch?feature=player_embedded&v=0cOlm28n_YE. This type of environment can raise a number of privacy issues that need to be addressed by providing users with control on whether each device is visible to others, whether the pages navigated on a device can be detectable by others, and whether a device can be a target of a migration. Such possibilities can be assigned only to specific users or groups of users.
Further issues can be generated in terms of security, including theft of private information from the migrated UIs, such as data entered by users (credit card, password, etc.) or data included in the page (bank profile, etc.) or information stored in forms, sessions, cookies. Other risks can be due to impersonating the user through authentication attack. Some of such issues can be addressed by automatically analysing the elements in the interactive forms in order to identify whether they can contain confidential data and, in this case, to handle their content in the migration process by using secure protocols, even if they were not used in the original application.