tical framework of a scientific school or discipline within which theories, laws, and gene- ralizations and the experiments performed in support of them are formulated”. The Oxford English Dictionary [168] defines it as “a world view underlying the theories and methodo- logy of a particular scientific subject”.
This section provides a brief overview of some emerging computing paradigms that em- phasise the interconnectivity and interoperability of multiple devices as their core concepts.
2.3.1
Ubiquitous Computing
Ubiquitous computing (abbreviated asubicomp; also known as pervasive computing) pre- sents the vision of seamless interaction among multiple computing devices embedded into everyday life [255]. Mark Weiser, the pioneer of ubicomp vision, proposed three basic forms for ubicomp devices as follows:
• Tabs. Wearable centimetre-sized devices. Smartphones and portable media players (e.g., Apple iPodTM) can be included in this category.
• Pads. Handheld decimetre-sized devices. Laptops, netbooks and tablets (e.g., Apple iPadTM, HTC FlyerTM, Samsung GalaxyTM) are included in this category.
• Boards. Metre-sized interactive display devices. Desktop computer, digital white- boards and large displays are included in this category.
In the words of Mark Weiser [255],
“Prototype tabs, pads and boards are just the beginning of ubiquitous computing. The real power of the concept comes not from any one of these devices; it emerges from the interaction of all of them.”
Due to the proliferation of computing devices of various form factors, as well as the in- creasing support for their interconnectivity and interoperability, the vision of ubicomp is gradually coming closer to reality. A thorough investigation of ubicomp enabling techno- logies is beyond the scope of this thesis.
2.3.2
Activity-Based Computing
Activity-Based Computing (ABC) is a paradigm within Ubiquitous Computing that focuses on the activity of the user to define interaction with computers [20]. In activity-based computing, the basic computational unit is no longer the file (e.g., a document) or the application (e.g., a word processor) but the activity that aggregates various computational services and data resources, and may include more than one participant (see Figure 2.2).
A user can initiate, suspend, store, and resume one’s computational activity on any com- puting device in the infrastructure at any time, and share it among several persons as well. ABC allows continuation of tasks across different computing devices and adapts the task to the computational resources of each device [21]. For example, high fidelity X-ray images can be shown on a wall-size display but a low-fidelity interface appears when the same task is resumed on a PDA. A detailed explanation of the ABC framework and the deployment of ABC-based experimental prototypes to facilitate collaborative work is presented in [21].
Figure 2.2: A computational activity aggregates a set of computational services, data resources and users (used with permission from [21]).
2.3.3
Recombinant Computing
Recombinant computing [158] is an approach to software infrastructures that aims at sup- portingserendipitousinteroperability i.e., the ability of devices and services within Ubiqui- tous Computing to access one another without having any prior knowledge of each other. It advocates the design of computing entities bearing in mind the consideration that they might be used in multiple ways, in different situations, and for different purposes [158].
This approach has been realised in the Speakeasy framework [157] that supports the provi- sion of user interfaces on multiple platforms. For example, the PDA shown in Figure 2.3 allows for manipulation of a presentation slide on a different platform even though the former does not have the software for presentation slides installed on it, and it has no knowledge of projectors or slide shows in the environment. A detailed explanation of the Speakeasy architecture is provided in [157] but is beyond the scope of this work.
Figure 2.3: Speakeasy: A PDA displaying the controller for a PowerPoint viewer running on a projector (used with permission from [157]).
2.3.4
Synergy of Multiple Devices
Below is a brief overview of the notions concerning synergies of multiple devices that appear in the literature.
Device Ensembles
Schilit and Sengupta [210] introduce the notion ofDevice Ensemblesthat refers to the wor- king of diverse computing devices in concert to give rise to an enhanced user interaction, similar to the ensemble of musicians that achieves a total effect greater than the sum of individual performances. A particular case of device ensembles is reflected in the cou- pling of mobile devices with large displays that can be used to make the most of input and output capabilities (e.g., the former’s easier physical accessibility and the latter’s bigger representation space) of each device.
Figure 2.4 shows the emerging ensembles of digital devices in everyday life. A compre- hensive discussion of enabling technologies and industry standards for device ensembles is
Figure 2.4: Ensembles of digital devices are emerging for common usage models at home, at work, and on the road (used with permission from [210]).
provided in [210], and lies beyond the scope of this thesis.
Cyber Foraging
The notion ofcyber foraging[8, 208] refers to augmenting the computing capabilities of a resource-poor mobile device by offloading some of the tasks to the computational resources (calledsurrogates) in the environment. A number of systems that support cyber foraging have been proposed [9, 58, 73, 227].
The emphasis of cyber foraging techniques is to enable mobile devices to use the under- lying infrastructure or system-level capabilities (e.g., greater processing power, battery life) of fixed computers for the remote execution of applications, and although not originally meant for it, they can support the sharing of the mobile device’s visual output on displays connected with the fixed computers.
Device Symbiosis
Borrowing concepts from biology, Raghunath et al. [179] present a notion of symbiosis between handheld devices and large displays in the environment where the former’s pre- sentation space opportunistically cause the latter to display content to the user. This notion has been realized in some prototypes. For example, the Personal Server [250] is an auxiliary device that enables a mobile phone to co-opt screens and keyboards of nearby computers through a WiFi connection. Berger et al. [27] present a prototype that allows a user to read an email received on a small handheld display by showing it on large displays.
The notion of device symbiosis is closest to the purposes of this research because it ex- plicitly supports the sharing of UI elements between handheld devices and situated large displays.