Keywords: design computing, situatedness, first-person knowledge, constructive memory.

This paper introduces the principles of situated design computing. Situated design computing expands the concept of computing from being the encoding of objective knowledge that is fixed by the programmers of the system to include first-person knowledge acquired while the programs are being used. This first-person knowledge forms the basis of the system's experience which is then made available as the system is used further. The four principles of situatedness are presented along with the basic concept of the mechanism by which such systems operate: constructive memory.

The paper introduces the distinction between first-person and third-person knowledge. Whilst much of human knowledge is objective, and is therefore third-person knowledge, i.e., it does not depend on the person that deduced it. There is a category of everyday knowledge that depends on the person rather than deduction. This knowledge is developed based on first-person interaction with the world. This class of knowledge is sometimes inappropriately encoded as deductive knowledge and in so doing often causes a mismatch between the experience of the person who encoded the knowledge and a subsequent user of that knowledge.

The four principles on which situatedness is founded are:

• Principle of Effect: what a system does matters
• Principle of Nonlinear Temporality: when a system does what it does matters
• Principle of Locality: where a system is when it does what it does matters
• Principle of Interaction: who and what a system interacts with matters

In addition to these four principles there is one lemma that provides the basis for the re-use of the first-person knowledge in the form of constructive memory:

• Lemma of Experience: what a system did before affects what it does now

Computationally memory has come to mean a thing in a location. The thing can take any form and the location need not be explicitly known. The thing can be accessed by knowing either its location or its content. There are a number of distinguishing characteristics of this form of memory:

• memory is a recall process
• there needs to be an explicit index (either location or content)
• the index is unchanged by its use
• the content is unchanged by its use
• the memory structure is unchanged by its use.

This is in contrast to cognitive models of memory, in particular constructive memory, which has the following distinguishing characteristics:

• memory is a reasoning process
• the index need not be explicit, it can be constructed from the query
• the index is changed by its use
• the content is changed by its use
• the memory structure is changed by its use
• memories can be constructed to fulfil the need to have a memory
• memories are a function of the interactions occurring at the time and place of the need to have a memory.

Situatedness and constructive memory together form the basis of a new kind of computing of potential use to designers called situated design computing.

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