Home > Embedding Plasticity in the Development Process of Interactive Systems
Embedding Plasticity
in the Development Process of Interactive Systems
Ga�lle Calvary, Jo�lle Coutaz, David Thevenin
CLIPS-IMAG, BP 53, 38041 Grenoble Cedex 9
http://iihm.imag.fr
{Joelle.Coutaz, Gaelle.Calvary, David.Thevenin}@imag.fr
This paper briefly presents our notion
of plasticity to denote a particular type of user interface adaptation.
We then propose a new process
model that supports a strcutured development of plastic user interfaces. The model is illustrated with a test case
example.
Key words.
User Interface adaptation. Plasticity. Model-based approach.
Information
technology is an increasingly essential part of the fabric and activity
of our lives. Jini-enabled information appliances, XML approaches to
information modeling and rendering, and gateways between Internet and
wireless network protocols, are being developed to cope with the pregnancy
of the technical push. This exploratory development of novel devices
and techniques is valuable in the short run. The approach, however,
is not replicable and provides poor guidance to sustain future development
of usable interactive technologies. As a result, there is a risk of
a shortfall between technical promise and effective interaction.
Theories and principles developed so far in HCI must not be lost in
the evolution!
Although principles of user-centered design methods and modeling techniques offer a sound substrate, pervasive computing opens the way to new challenging requirements. In particular, people want to have the choice. They want to be able to choose among a wide range of software platforms and hardware devices to accommodate multiple needs depending on places and spaces across time. Providing different interfaces specially crafted for each type of device and modality combination is extremely costly and could result in users having many different versions of interfaces on different devices. The impact of this includes massive under-use of interfaces potential and excessive development costs to maintain versions consistent across multiple platforms. In [Thevenin 99], we introduce the notion of plasticity to cope with these problems.
The term "plasticity"
is inspired from the property of materials that expand and contract
under natural constraints without breaking, thus preserving continuous
usage. Applied to HCI, plasticity is the capacity of an interactive
system to withstand variations of context of use while preserving
usability.
A context of use for a plastic system covers two classes of attributes:
A plastic
user interface preserves usability if the properties selected at
design time to measure its usability are kept within a range of values
as adaptation occurs to contextual changes. Although the properties
developed so far in HCI [Gram 96] provide a sound basis, they do not
cover all aspects of plasticity. For example, they do not express the
need for continuity [Graham 2000] when migration occurs between contexts
of use. Thus, we need to extend and refine our apparatus of properties
to cope with the new situations offered by the technology.
Activity theory takes into account the situation of action early in the design process. Unfortunately, situation-dependent information is lost in the development process due to the lack of appropriate notations of the design and development tools. As a result, current tools implicitly assume that users are working with a desktop computer located at a specific place. A notable exception is the context toolkit [Salber 99] developed for encapsulating sensors at the right level of abstraction and the "literate development" [Cockton 95]. Although within the scope of plasticity, context toolkits cover low-level technical concerns only, and the literate development is not precise enough to address our problem. Therefore a process model that supports the development of plastic user interfaces is required. This is the topic of a subsequent section illustrated with a sample case.
The heating control system envisioned by EDF (The French Electricity Company) will be controlled by users situated in diverse contexts of use. These include:
a) b)
Figure 1.
a) Large screen. Temperature of the rooms are available at a glance.
b) Small screen. Temperature of one room is displayed at a time.
A typical user's task consists of consulting and modifying the temperature of a particular room. Figures 1 and 2 show versions of the same system for different interaction platforms.
Figure 2 shows
the interaction trajectory for setting the temperature of a room with
a WAP mobile phone. In 2a), the user selects the room (e.g., le salon
– the living room). In 2b), the system shows the current temperature
of the living room. By selecting the editing function ("donner
ordre"), one can modify the temperature (2c). When comparing with
the situation depicted in Figure 1, not only navigation tasks have been
introduced, but a title for every deck (i.e., WML page) has been added
to recall the user with the current location within the interaction
space.
Figure 2.
Modifying the temperature using a WAP-enabled mobile phone.
All of these alternatives have been produced using the following framework.
Our framework is intended to serve as a reference instrument to help designers and developers to structure the development process of plastic interactive systems. To this end, we adopt a model-based approach [Paterno 99]:
Figure 3 shows
the models involved in the process. The Platform Model and the
Environment Model define the contexts of use intended by the designers.
The Evolution model specifies the change of state within a context
as well as the conditions for entering and leaving a particular context.
The Interactors Model describes "resource sensitive multimodal
widgets" available for producing the concrete interface.
Figure 3. The reference development
process for supporting plastic interactive systems.
All of the
above models are referenced along the development process from the task
specification to the running interactive system. The process is a combination
of vertical reification and horizontal translation. Vertical reification
covers the derivation process, from top level abstract models to run
time implementation. Horizontal derivations, such as those performed
between HTML and WML content descriptions, correspond to translations
between models at the same level of reification. Reification and translation
may be performed automatically from specifications, or manually by human
expert designers depending on the tools available.
As shown in Figure 4, the reference framework can be instantiated in many ways:
Figure 4. Instantiations of the reference model.
In summary,
the technology push provides opportunities for new forms of interaction
and triggers new social requirements.
New forms
of interaction. Although prospective development may be fun and
valuable in the short run, we must not put aside the principles and
theories developed for the desktop computer to design new artefacts.
Instead, we propose to use current knowledge as a sound basis, question
current results, improve them, and invent new principles if necessary.
This is the approach we have adopted for supporting plasticity by considering
model-based techniques from the start. Because automatic generation
of user interfaces has not found wide acceptance in the past [Myers
00], reification and translation may be done manually by human experts
when tools are inappropriate.
New user's requirements. People are craving for wide ranges of choices (anything, anywhere, any time). Our concept of plasticity addresses one aspect of these new requirements while attempting to minimize the cost of developing and maintaining such systems. Our framework, although incomplete, provides a reference structure for coping with this complex problem.
This work is being supported by EDF, France.
[Cockton 95]
G. Cockton, S. Clarke, P. Gray and C. Johnson. Literate Development:
Weaving Human Context into Design Specifications. In Critical
Issues in User Interface Engineering, P. Palanque & D. Benyon Eds.,
Springer-Verlag: London Publ., ISBN 3-540-19964-0, 1995.
[Graham 2000]
T.C. N. Graham, L. Watts, G. Calvary, J. Coutaz, E. Dubois, L. Nigay.
A Dimension Space for the Design of Interactive Systems within their
Physical Environments, DIS2000, 17-19 August 2000, ACM Publ. New York,
pp. 406-416
[Gram 96] Gram,
C. et Cockton, G. Ed., Design Principles for Interactive Software. Chapman
& Hall, 1996.
[Myers 00]
B. Myers, S. Hudson, R. Pausch. Past, Present, Future of User Interafec
Tols. Transactions on Computer-Human Interaction, ACM, 7(1), March 2000,
pp. 3-28.
[Paterno 99]
F.Patern�, Model-based Design and Evaluation of Interactive Applications,
Springer Verlag, November 1999.
[Salber 99]
D. Salber, A. K. Dey and G. D. Abowd. he Context Toolkit: Aiding the
Development of Context-Enabled Applications. In the Proceedings of the
1999 Conference on Human Factors in Computing Systems (CHI '99), Pittsburgh,
PA, May 15-20, 1999. pp. 434-441.
[Thevenin 99]
D. Thevenin, J. Coutaz. Plasticity of User Interfaces: Framework and
Research Agenda. In Proc. Interact99, Edinburgh, A. Sasse & C. Johnson
Eds, IFIP IOS Press Publ.. , 1999, pp.110-117.
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