A Population Approach to Ubicomp System Design

Adding and removing modules (also called plug-ins, add-ins and other names) without technical support or supervision is becoming the norm for everyday software applications such as web browsers, image editors and email tools, e.g. Firefox, Photoshop and Outlook. This same approach is becoming important in mobile phone software, where 'in-app purchase' of modules is becoming more and more popular, and a huge money-spinner for developers.

The consequences are not all good: users often do not know which modules to use or change, to suit their goals, or whether a program will crash after such changes. As a result of modules being from different developers, their combination may never have been tested prior to public use. Evaluators and developers struggle to help, because established approaches to software definition, design and analysis are based on the structure of a program being the same wherever and whenever it is used. In constrast, one would be hard put to define a single software structure that accurately describes what a program like Firefox is. Use is similarly hard to pin down, as individuals make systems fit with their own uses and contexts, and share their innovations with others.

As a modular program becomes complex, the result is often a 'plug-in hell' of broken software dependencies, functions, uses and expectations. If, instead, software structure is kept simple, then design opportunities are lost as developers avoid the difficulty and cost of implementing innovative programs. More generally, software theory and engineering have fallen behind practice. We lack ways to reason predictively in a principled way about real world structure and use. We lack tools for designers, evaluators and users that support adaptation, and we lack principles and techniques that can deal with the scale of human and software interaction.

Our primary objective is to deliver a new science of software structures, with design, theory and tools that reflect software in real world use, and able to tackle the complex problem of how to design to support change and appropriation. The key concept is the 'software population': a statistical model of the variety we see when we look at how the same initial program has been used and adapted by its users. A population model is kept up to date by each instance of a program logging how it is used and changed. The population idea affords a common design vocabulary for users' understanding and adaptation of programs, for evaluators' analysis of programs in use, and for developers' making informed changes to the modules available to users.

As a result, users will have programs that may vary but are more comprehensible, robust and adaptable than is the case today. We will enable each individual user to make a practical decision that only he/she is qualified to make: how to balance the changed robustness and functionality of one's system with changes to the system's support for individual and social interactions. One will have tools built into one's program that makes clear what it consists of, and how its structure relates to the programs and experiences of other users. One can find out about other modules that are compatible with one's program, how it will work after adding in one or more new modules, and therefore which configurations of modules will and will not work.

In order to test whether the approach works at the scale of, for example, typical iPhone applications, we will build and deploy programs among large numbers of users, for weeks or months-mobile games and social networking applications. We will work with industrial partners including the Edinburgh Festivals, as well as using popular sports and events, such as soccer (e.g. the 2014 FIFA World Cup Brazil), athletics (e.g. the London 2012 Olympics and the Glasgow 2014 Commonwealth Games), and popular TV programmes. Overall, We plan for 500,000-1,000,000 users of our systems in the course of the programme.

This programme involves advances in knowledge of direct relevance to those involved in the design, construction and use of systems based on modules, plug-ins and similar software infrastructures. These advances will include a new approach to fundamental computer science concepts, in particular 'class', as well as practically oriented results such as tools and infrastructures for large-scale public deployments of applications. Key aspects and examples of our approach will be packaged as high-level guidelines and case studies, open source code with tutorial demonstrator examples, and the broader evidential record of code and data that will be released in its final form at the end of the programme. These resources will collectively form empirical evidence of the theoretical concepts' validity and significance, and the technical effectiveness and social acceptability of system construction based on these concepts.

We will promote the new approach within our research communities, by maintaining our strong publication record in premier journals and conferences, organizing workshops and tutorials at premier conferences, and presenting our work at leading research institutions. The programme will have a significant impact in increasing the UK's capacity to undertake interdisciplinary research that spans between academic and industrial concerns. We will help develop the next generation of research leaders by exposing the RAs/RFs and interns to a world-leading interdisciplinary environment, in which research is expected to be both pioneering in terms of academic quality and yet grounded in terms of relevance and utility in large-scale real world deployments.

As a result of our work, the general public will have programs that may vary but are more comprehensible, robust and adaptable than is the case today. The general public and the education sector can benefit from learning about, and experimenting with, population-based application design and associated analysis tools, so as to understand their everyday implications. We will pursue opportunities for outreach and advocacy among the general public, industry and the wider scientific community, e.g. demonstrations and displays at science festivals, trade fairs and industrial outreach events, and debate through learned societies. Part of this outreach is inherent in our large-scale deployments, which will engage with 500,000-1,000,000 users over the lifetime of the programme. We will continue to use press coverage to inform the public and industry of our work. Benefits will start to accrue during the project and many of the demonstrators will focus on activities that aim to engage with the general public. Taken together, these points make for high impact research carried out in a very public way, which is one of the distinctive features of this research endeavour.

Policy makers will benefit from considering new avenues for introducing new socially acceptable policies, using knowledge about people's reaction to public deployments and case studies. Benefits are likely to accrue starting late on in the programme, in a 4-6 year timescale, drawing upon the programme's case studies and evidential record.

Industrial beneficiaries will gain from exposure to the development and deployment of technologies that have demonstrated their potential for exploitation in products for mass markets. The benefits are likely to accrue as collaborative research and spin off projects within the programme, and independent development within 1-2 years of the end of the programme. Collaborating partners will benefit from access to the leading researchers in this new area, the ability to shape the ongoing research as it happens, the exchange of staff through inward and outward secondments, and the ability to demonstrate and evaluate the work in deployments aligned with their commercial areas of interest.