Lessons learned from manual systems: designing information systems based on the situational theory of agency - Information Systems Foundations: Constructing and Criticising - page 173

ility and quantity of parts holdings are clearly seen on the shelf. The only recorded re-
quirements-related information is in the reference to non-standard choices on the
whiteboard.
If this system were to be explained by the deliberative theory of agency, representation
would include detailed information about each compressor being manufactured. This
is not the case in the Cash System where very minimal information is kept explicitly on
the whiteboard. No rules can be found to enable a worker to take the individual parts
and assemble a compressor. Instead we see the next action being selected by the partly
manufactured machine being presented to the worker. Only a limited range of choice is
available to them. The worker knows what happens next because there is very little
(often no) choice confronting them. When there is a choice, the whiteboard tells them
the option to be selected based on the customer's desires.
The Cash System is a highly situational one where representation is almost absent. Action
is selected by routinely acting on the partly manufactured machine based purely on the
current status of the machine. In the Cash System, 'the world (is) its own model' (Brooks,
1991) in that the machine 'jigs' itself and parts are visible, obviating the need for stock
data. Consequently, the current situation is found in the visible state of the stock on the
shelf, the number of jobs on the floor, the condition of the partly manufactured com-
pressors that are the jobs on the floor, and the markings on the whiteboard. Due to the
careful design of the factory layout, all these are immediately visible to a worker. In
addition, the use of a single small whiteboard allows the foreman to grasp the total
production situation at a glance. The recorded information on the whiteboard is largely
ephemeral (except for a small amount of recorded information for warranty purposes
that is kept in a topic). When a job is finished it is removed from the whiteboard and
the new situation is revealed.
Large-scale lean manufacturing: the Kanban system
The Japanese Kanban system (Schonberger, 1987; Womack et al., 1990) is widely used
in the automotive industry for the activity of replenishing parts for production. Kanban
is the Japanese word for 'card' and the movement of cards in this system controls stock
levels and replenishment activities. For each part there is a fixed size container. A Kanban
has printed on it minimal information about the item it is used for, usually product ID,
the primary supplier and the workstation where the part is used (see Figure 14.4). There
are a fixed number of Kanbans in existence for each item and, except when desired
manufactured capacity changes, they are neither created nor destroyed.
Figure 14.4. A typical Kanban card.