Lessons learned from manual systems: designing information systems based on the situational theory of agency - Information Systems Foundations: Constructing and Criticising - page 167

In the past 30 years a number of methodologies have been developed to assist in
designing such systems. These are often called information engineering methodologies
(IEM), with Structured Systems Analysis and Design Methodology (SSADM), the British
government standard, being a typical example. These design methodologies share the
ontological assumptions of the deliberative theory, namely, that systems should represent
the world in which the system acts in terms of external, independent and objective en-
tities, properties and relations (Wand et al., 1995). Given this focus on symbol/object
representation, use of these methodologies encourages designs for socio-technical systems
in which the information systems form the representational scheme which mimic the
deliberative approach to agency.
On the other hand, disciplines other than information systems have considered an altern-
ative approach called the situational theory of agency. In robotics, specifically, this al-
ternative theory has been motivated by the brittle performance and computation intensity
of artefacts based on the deliberative approach. The key to this alternative theory is to
provide an agent with largely reactive responses based on sense data obtainable directly
from the agent's ground view of the world, and to introduce the agent's goals and per-
spective explicitly in the representation schemes implicit in the theory. In the situational
theory, agents respond reactively to 'situations' without deliberation. Situations are
descriptions of the world centred on the agent and only include features of the world
that relate to the agent's purposes (Agre and Chapman, 1987). These features consist of
the relations of things to the agent given its goals . Actions are selected from a repertoire
used to respond to situations. This approach to action selection leads to goal attainment
only if the agent's environment exhibits structure ('affordances') that obviate the need
to plan (Agre and Chapman 1987). An affordance is a structural aspect of the environment
that makes it possible for an agent to reach a desired situation by merely reacting to its
current situation. Analysis and exploitation of environmental structure is an important
part of designing situated agents (Agre and Horswill, 1992; Hammond et al., 1995;
Horswill, 1995; Agre and Horswill, 1997). An activity in this theory is a grouping of
situations and associated actions that together lead to a reliable reaching of a desirable
situation.
We can see the differing roles of representation in the situational theory. Situations are
agent-centred and intention-laden. Representation of situations on the basis of a sym-
bol/object isomorphism is neither possible nor necessary. An agent responds to being
in a situation by taking an action. An agent needs to notice that it is in a situation and
does so by sensing aspects of its environment. Consequently, aspects of situations are
needed to fire situation-action responses. Agre and Chapman (1987) argue that the rep-
resentational scheme is 'indexical' and 'functional' in nature. Indexical representations
describe things relative to the agent and functional representations select things according
to their relevance for the purposes of the agent or concern the activities in which the
agent is engaged. Further, Agre and Chapman (1987) argue that to eliminate the compu-
tational complexity of action selection inherent in using aerial world models, indexic-
al/functional representations of situation features that are relevant to the agent's goals
are rebound 'on the fly'.
The reliance of the situational theory on indexical/functional rather than symbol/object
representation shows it is built over different ontological categories: situations, aspects
of situations, actions, activities (groups of situation/action pairs), environmental structure,
and environmental affordances .