
Empirical Modelling, Radical Empiricism and the Management of Knowledge

Meurig Beynon, Steve Russ

Computer Science, University of Warwick, Coventry CV4 7AL

Philosophy / Knowledge / Knowledge Management


1. Empirical Modelling

Empirical Modelling (EM) is a term that has been introduced to describe principles and tools that support an unusual kind of computer-based model-building. The development of this approach has been the subject of an extended research programme at the University of Warwick, primarily directed by the authors of this paper, that originated with the design of a notation for interactive graphics some 20 years ago (see http://www.dcs.warwick.ac.uk/modelling). EM is unusual in that it represents a form of modelling oriented towards capturing 'state-as-experienced' and leads to the construction of computer-based artefacts that have no preconceived or formally circumscribed behaviour. It will be helpful to put this claim in context before presenting concrete evidence to illustrate it.

1.1. The nature of EM models

It is a commonplace fundamental notion of computer science that the significant semantics of a computer program is captured in the algorithmic behaviour that it implements. This notion leads on to the idea that all legitimate computer use is necessarily essentially concerned with specifying and implementing abstract behaviours. Whilst computer science acknowledges the need to design interfaces through which the user can direct or monitor computer behaviours, this is typically seen as beyond the remit of the core science of computing. Such a view of core computer science as fundamentally concerned with abstract mathematical concepts of computation and behaviour is curious in view of key trends in the historical development of computing practice.

The use of the computer - or more precisely of computer-related technology - to generate so-called Virtual Reality (VR) environments epitomises some of the most significant issues. If a VR environment is to have the qualities of a reality such as we experience in our everyday life, the character of the interface to the underlying computer model of state is a crucial rather a peripheral issue. In a real environment, the user can observe the environment in ways that have not been preconceived, and conduct authentic measurements and experiments. It may be possible in principle to conceive how such a real environment can be implemented if we accept a reductionist view of reality and a logicist account of human intelligence. Such a conception is of little interest either to the computer practitioner or to the user, whose view of construction and use is guided by pragmatic concerns. For instance, we should not necessarily expect to have perfect knowledge in order to construct an environment to assist us in the task of 'knowledge management'. In any event, an environment in which only knowledge that has been previously encoded is recoverable is of limited use.

Viewed from the classical computational perspective, the idea of building computer-based models that offer the user more than has been consciously encoded by way of 'use cases' (cf. [Jac]) seems paradoxical. To see this from another perspective, it is helpful to consider other model-building activities, such as those associated with what Levi-Strauss characterises as bricolage [LeviS]. In bricolage, the modeller's concept of the artefact under construction develops in conjunction with the artefact itself: the modeller gains feedback from experience of the unformed artefact itself, and uses this feedback to guide its further development. To the extent that prototyping plays a part in computer program development, practical computer programming can be viewed in this light. In practice, feedback routinely affects the bricoleur's conception of the developing artefact in a much more radical way than prototyping affects software development. The bricoleur is not constrained by the pre-established conventions for interpretation that typically frame a software product: in contrast, the way in which the artefact is to be interpreted and used is in many aspects ill-defined and open to negotiation throughout its construction. EM may be seen as offering an approach to model-building with the computer that has these key characteristics in common with bricolage.

The classical view of computation is complementary to a classical view of knowledge. The concept of building programs that are otimised to serve a specific narrow function, and of encoding information in formal data structures, promotes a prosaic view of what knowledge and knowledge representation entail. Knowledge is seen as something to be possessed that can be expressed and recorded as a proposition, as in "I know the telephone number of staff member X". This view is appropriate in its proper context, as is implied by the use of the expressions 'perfect knowledge' and 'only knowledge that has been previously encoded' above. It makes sense to speak of recording the telephone numbers of all university staff in a directory, and - in the absence of any further context - it would be absurd to search this directory for those who are blue-eyed and can play the bassoon. On the other hand, it is evident that developing a VR environment involves much more than encoding abstract knowledge about a real-world domain. A key issue is how knowledge about the domain is reflected in the interactive experience that the environment offers to the user.  

EM differs from classical computer-based model-building in its relation to both computation and knowledge. The distinction between an EM model and a computer program is analogous to the 'real-world' distinction between an open environment and a circumscribed procedure. To be familiar with an EM model is analogous to being familiar with a city; to be familiar with a computer program is analogous to knowing how to use the underground to get from one station to another. It is helpful to think of the EM model as something organic that grows and changes over time: there is no sense in which being familiar with a city is a limited notion - we explore and observe more of a city over time; the city changes; we change in our response to the city; we change the city. There is no reasonable sense in which familiarity with a city can be comprehensively preconceived, in any moment, we can at most testify to what is familiar in the particular aspect of the city of which we have immediate and direct experience. Though I may tell you with conviction that the cathedral is out of sight but lies just around the corner, I appeal to my memory and to my faith in the permanence of place, and know what only the act of taking us to the cathedral can confirm. An EM model is more general than a computer program in much the same way that 'knowing how to use the underground' sits within the broader framework of 'being familiar with the city'. The analogy also helps to illustrate the ontological distinction between the model and the program. If we take the permanence and reliability of a city environment and the generic and routine nature of our observation of underground transport for granted, then 'knowing how to use the underground' is a skill that can be viewed as independent of any particular city, that can be exercised without engaging with the total experience of 'becoming familiar with the city'. It is possible to imagine how a robot can be programmed with the stimulus-response patterns needed to use the underground, but much harder to conceive what might be meant by programming a robot to get to know a city.

The metaphor of "knowing the city" is helpful when understanding both the way in which an EM model is realised on a computer, and the philosophical stance it reflects on knowledge. As I look out of my study window at this moment, my view of the city of Coventry is limited to the roof of my neighbour's house and the sky above. In my imagination, I can trace the path from the house to the city, though the act of tracing this path is no part of my present direct experience. My knowledge of Coventry invokes the conjunction in my memory of all the direct experiences I have had over many years of different aspects of the city. There is no sense in which all these prior experiences can be taken as one experience, any more than I can be in more than one place at once. From this perspective, the 'perfect knowledge' on which we might aspire to base a classical computer-based model of the city is a mere chimera. What there is to be known of Coventry is more than I can ever experience, and my personal knowledge is established, maintained and revised dynamically through my ongoing interactions with it. Even my current limited view of the city is potentially open to such elaboration of knowledge, now that I notice the pigeon droppings on the crest of the roof, the silver sliver of a distant passing plane, and savour the taste of lukewarm lime juice cordial. As a source of direct experience, an EM model cannot compare with my everyday Coventry environment in its richness, but it offers access to potential experience and knowledge with which I can engage in similar ways. In effect, it supplies an interactive artefact with which to trace a history of experiences that is similar in character to our everyday experience of purposefully and accidentally developing our knowledge of a city. In this activity, the computer serves two significant roles: it serves as a physical artefact, similar to the artefacts of bricolage, that generate direct experiences to which the modeller can make a creative response, and at the same time it allows the modeller to record and elaborate experiences as they are encountered in 'the stream of thought'. In these respects, the computer offers support for managing knowledge as it is characterised by Petsche [] as 'interaction with memory'.

1.2. An illustrative case-study

Empirical Modelling principles and tools were not initially developed with the general characteristics of EM models, as described above, in mind. Our present understanding of the characteristics of EM models was arrived at after first appreciating the difficulties of providing a formal semantics for such models within the classical theoretical framework for computation. Two sources of inspiration have been particularly significant in reaching this understanding: a large body of practical work on model-building and tool development that has been carried out largely by computer science students at Warwick over the last 15 years, and the philosophical writings of William James []. This subsection will give a brief sketch of practical EM with reference to a model of a lift initially developed in a summer vacation project in 1994 []. (The lift model and the EDEN interpreter which is needed to run the model can be downloaded from the EM website ... .) The next section will then discuss EM in relation to William James's philosophic attitude of Radical Empiricism [].

Figure 1 depicts our EM model of the lift as it might be displayed in one particular state. The lift car appears on the left, and the five floors that the lift visits on the right. The stick figures are used to indicate the current locations of lift users: a label attached to the head of each stick figure identifies the list of users at each location. The bold vertical lines between the lift shaft and the floors represent the status of the doors between the lift car and each floor: the door on the fourth floor is currently open. The small boxes to the right of the floors and to the left of the lift car are call buttons, and those that are currently selected are indicated in bold.

To interpret Figure 1 as associated with a direct experience of an actual lift, it is helpful to think of looking at a glass lift at the side of a five storey building. Whether this is representative of the direct experience that is of primary interest to the modeller depends upon the role in which the modeller interacts. Examples of possible roles that the modeller might play, possibly concurrently, include: a lift user, designer or analyst, or perhaps even a story teller for whom a lift is a significant location (e.g. as the venue for murder in a detective story).  In practice, if we have any familiarity with lifts (even if we are in the position of user X in Figure 1, with limited access to the actual current status of the lift), we bring to our interaction with them a general concept that  there are floors and users and a lift car that moves vertically between them, and may be expected to visit the ground floor at some stage in response to pressing the call button.

In our modelling tool (EDEN), the current status of the lift is determined by the current values of its characteristic observables. The names of some of the key observables, as they are recorded in our model-building interpreter, are:

_liftfloor	- where is the lift? [on which floor: 1-5]
_open3	- is the door open at level 3?
_car2	- is button 2 in the car selected?
_button4	- is the call button on floor 4 selected?
locX		- where is user X?  [0: in lift, 1-5: on which floor, 7: nowhere]
_inliftX	- is user X in the lift?	
_destX	- where is user X intending to go?

The values of most of these observables are directly reflected in features of the display. For instance, _liftfloor determines the position of the lift, _open3 determines how the line on floor 3 is depicted and _button4 determines whether the call button on floor 4 is highlighted. A feature of EDEN is that these features of the display can themselves be construed as observables whose values are specified by definitions resembling the definitions that relate the cells of a spreadsheet. Taken together, the definitions of observables, whether explicitly by values, or implicitly via formulae, form a 'definitive script' that specifies the current state of the model. The term 'definitive notation' is used to refer to the underlying notations used to formulate a script. EDEN includes a definitive notation for defining the screen layout and for defining planar line drawings. The use of these notations is illustrated in Figure 1. 
	
The definitions in a script express expectations about how the values of observables are linked where 'atomic' changes are concerned. For instance, when the lift moves, anyone in the lift moves with it as part of one and the same state change. The relations linking these changes are called 'dependencies' between observables. For example, using carpos and posX respectively to represent the positions of the lift car and of user X (as depicted by 2D coordinates in Figure 1), the definitions of the following general type express dependencies:

	carpos is {liftshaftL , (_liftfloor-1) * floorheight}
	posX is if _inliftX then carpos else floorX
	_inliftX is (locX == 0)
	
The use of a definitive script to represent state-as-experienced is the fundamental technique by which a modeller constructs environments for interaction in EM. Such an environment is typically oriented towards expressing the perspective of a particular agent where both observation and interaction are concerned. In this context, an agent is anything that might be deemed to be responsible for changing the current state of the EM model. The archetypal agent is the modeller who acts to change the state of the model through manually entering redefinitions of observables into the EDEN input window. As will be discussed and illustrated later, the lift users and the lift itself can also be viewed and in various different ways animated as agents with some autononous capacity to change state. In viewing the EM model, it is important to understand its primary role as a representation of state-as-experienced, rather than merely as a vehicle for automating conventional lift behaviour. To return to the analogy introduced above, animated behaviours in EM are in the first instance like bus tours of the city: by default, we observe the city according to a preprogrammed plan, but there is nothing in principle from to prevent us from leaving the organised party and continuing our exploration independently. 

The idea that the lift model captures state-as-experienced can only be appreciated by considering the possible modes of interaction with it that are open to the modeller. It is helpful to reflect on the distinction between the abstract interaction that is involved in using the underground and that involved in making the same journey above ground. In the former context, the traveller can get by by pattern matching, relying on the way in which the underground environment itself is built to encode knowledge about locations and directions in place names, keywords and icons. In the latter context, the personal knowledge of the traveller - their ability to recognise landmarks, to maintain a sense of direction, to devise strategies for crossing roads, to be able to consult other people - is paramount: though the environment itself has embedded knowledge in the form of signposts and streetnames, the logistics of their use are by no means fully systematised. In practice, both opportunistic and exploratory human interpretation and pre-coded knowledge play their part in navigation in a city environment. In a similar way, interaction with the EM model of the lift can either give prominence to how human intelligence informs state transition or support routine and automatic interaction. What is more, commitment to changing the model is not necessarily required in playing these different interactive roles, and either can be highlighted according to purpose.

The openness of the modeller's agency in EM is the platform for intelligent interaction. The modeller is free to redefine any of the observables in the script subject only to being able to interpret the consequences of such redefinition. As a simple example, a redefinition such as

carpos is {liftshaftL , 0}

relocates the lift car at the base of the lift shaft as if it were out of service. Note that this redefinition in some sense 'deals intelligently with user Z': in the context of Figure 1, it would move user Z within the lift no matter where the lift was placed. Actions of this open-ended nature are analogous to the unconstrained actions that the traveller can make in the city environment, that may result in reaching the destination inadvertently, might lead to getting lost or to being run over.

To illustrate how knowledge about meaningful interaction can be exposed without being encoded in an EM model, the lift model has been adapted and used to animate a specific scenario, namely the true tale recounted by the first author in Box 1. For this purpose, the modeller has only to compile a sequence of elementary redefinitions of observables to reflect the actions of the users and the lift as they occur. By playing through this sequence of redefinitions, the modeller can visit each situation as it arises, and reflect upon the perceptions and motivations of the various agents involved. The modeller can then construct a narrative to document their informal understanding of the scenario. The EDEN interpreter provides a procedural construct for playing out this sequence of redefinitions as if they were being entered one-by-one by the modeller. Such a sequence can be accompanied by a commentary that gives more insight into the complex combination of observation and logic that guides each lift user's actions.

----	Box1 ----

I am at a conference in the Netherlands.
I arrive late at night and hardly notice where my room is. 
Next morning, I notice that my room is on the top floor.
I walk down to breakfast thinking about my talk later on.

After breakfast I meet two other delegates X and Y.
We get in the lift to return to our rooms.
X presses the button for floor 4.
Y says he is on the floor above X, and selects floor 5.
Since the top button is selected, I don’t press a button.

We talk as we ascend. The lift stops. The door opens.
The floor numbers aren’t clearly marked.
I say to X ‘this must be floor 4' - he gets out.
Y and I carry on talking.

When the lift next stops, the floor is still unclear.
I say to Y ‘X is on the floor below you; this is your floor’.
Y gets out. I think something is not quite right.
I think ‘is this the top floor?’ and ‘should I get out?’.
I’m unsure, but notice that the button for floor 5 is still lit.
I proceed to the top floor which is the next floor, floor 5.
When I get out of the lift, I can’t find my room.

There’s no room where my room is on floor 5.
I walk down to floor 4, and pass Y on his way to floor 5.
When I reach floor 4, I meet X coming up from floor 3

How did I manage to get all three of us to the wrong floor?
--------
Box 1 : Travails in a lift
-------------

Figure 2 depicts a critical moment in the scenario, at which it becomes clear to user I that there is some conflict between what I observes and the way in which I had conceived X and Y's interaction with the lift up to this point. I supposes that his room is on the top floor, and realises that the lift has not yet reached the top floor. On the other hand, on entering the lift, I observed the selection of just two buttons by co-users X and Y, and noted that one of these corresponded to the top floor. It would seem from this that I should have got out at the same time as Y.  It was just after Y got out of the lift that I realised that perhaps he had misled X, and that the lift had in fact stopped at floor 3 when called by an impatient user Z.  At that point, it was apparent to I that both X and Y had got out at the wrong floors, but not that he himself was also about to travel upwards to the wrong floor. The extra detail of the profile of the building that has been introduced in Figure 2 represents the other element in the situation by which I himself was misled into supposing that his room was on floor 5 rather than floor 4: in the vicinity of I's room, floor 4 was the top floor. The pragmatic nature of the decision that I makes at this point, so different in character from the pure reasoning that is sometimes imputed to human agents (cf the Mensa problem discussed in [Founds of AI]), is emphasised by the real time constraints on decision imposed by the lift itself. 

Figure 2 can be interpreted as the particular specialisation of the vanilla model of the lift depicted in Figure 1 that I ideally should have had in mind in using the lift. In practice, I was not able to construct this model in real-time, and acted on the basis of a different construal. A crucial aspect of the EM model is that it relies essentially upon physical artefacts to account faithfully for I's misunderstanding. The geometric content of the model, limited as it is as far as realistic details of the physical environment are concerned, has rich experiential significance. It is to remembered observation of physical models such as are depicted in Figures 1 and 2 that we appeal in using a lift, and the experience of interacting with these models that exposes their role in representing our knowledge of lifts. Needless to say, many attempts have been made to abstract the essence from such experiential representations in logicist approaches to knowledge representation (cf. [Blocks1 and 2]). In practice, there are many other pertinent issues connected with the experience of lift use that influence the behaviour of users, many of which are only tacitly acknowledged even in our account of the scenario described in Box 1. These issues include: the nature of the experience - the time it takes a lift to move between one floor and the next, the relative time it takes to ascend 3 rather than 4 floors,  the acceleration of the lift car; the nature of the auxiliary observation that might have affected user responses, as determined by the status of the buttons of the lift, the visual cues to distinguish different floors, whether and how the users' room keys and the lift car buttons were numbered; the implicit conventions framing the lift design and use, such as whether the ground floor was deemed to be floor 0 or floor 1, the fact that the buttons in the lift were ordered top to bottom in a 1-dimensional array in correspondence with the five floors, or that a call button in the lift was visibly deselected when the door opened at the corresponding floor.

As the above discussion illustrates, the EM model of the lift offers insight into real world state-transitions about which the automation of the perfect lift user can give no information. Interaction with Figure 2 offers a plausible explanation for corporate behaviour that is absurdly different from the ideal outcome to be expected, but it also shows that - taking appropriate observational and experiential factors into account - the individual actions of the users are not so very far from sensible as they might appear. Logic alone cannot account for the scenarios that lie near to the routine 'in the neighbourhood of sense'.  In exploring such scenarios fully, there is no alternative but to allow the modeller to engage as freely as possible in the state-changing activity. In the spirit of Gooding's definition of the term, an EM model can be interpreted as a construal []. In constructing such a model using EM principles, our aim is to embody the patterns of observables, dependency and agency that we deem to be characteristic of a situation. The product of this activity typically has a personal, provisional and particular character that is intimately connected with the ways in which we choose to interact with it. In all these respects, it is unlike a formal specification.  

In developing a construal, the modeller is not only concerned with modelling state change as it is observed from an external perspective. A further analysis of the sequence of redefinitions that are made in realising the scenario in Box 1 shows how certain groups of redefinitions can be attributed to different agents. The movement of the lift and the manipulation of the lift doors are part of the automatic behaviour of the lift system itself. Entering and leaving the lift and the selection of call buttons inside and outside the lift are actions for which the lift users are responsible. To refine the model so that it better reflects our understanding of normal lift operation, it is appropriate to distinguish between realistic transitions and transitions that are pure fantasy, such as might involve simulating a user entering the lift before the door is open, or the lift jumping between floors. EM includes techniques for enriching the lift model so as to give special prominence to construals suited to different perspectives and purposes, some of which may include automated behaviour, or reflect several viewpoints concurrently. It is important to realise that the specialisation of an EM model does not involve excluding singular actions on the part of the modeller. In some circumstances, such as when the lift cable breaks, it may be appropriate for the lift to exhibit abnormal behaviours that can only be simulated by the intervention of the modeller in the role of a superagent. The EDEN interpreter is designed to support the opportunistic interaction by the modeller that is required for this purpose, but whether such privileges for interaction are exercised is entirely at the modeller's discretion. A brief review of some relevant EM techniques is given here - for more details, consult ... .

In elaborating construals, a significant role is played by an informal special-purpose notation, called LSD, that can be used to classify the observables in a situation with respect to an agent. The aim of such a classification is to document the roles that observables play in determining the interaction of an agent. Listing 1 is an LSD account of a person X in the role of a prototypical user of the lift depicted in Figure 2:

agent person (X) {
	state	loc[X]
	role liftuser {
		state 	dest[X]
		oracle 	open[*], dest[X], loc[X], pos[X]
		handle 	loc[X], dest[X]
		derivate 	pos[X] is if loc[X]==0 then liftfloor else loc[X], 
				LIVEliftuser[X] is 0<=loc[X]<=5
		protocol
			loc[X]==0 and open[dest[X]] and pos[X] == dest[X] -> loc[X] = pos[X],
			true -> dest[X] = i ,						(1<=i<=5)
			...
	}
	...
}

Listing 1: An LSD account of a prototypical lift user

In this account, the observables loc[X] and dest[X] refer to the location and destination floor of user X respectively. The values of these observables are defined according to the same conventions used to define locX and destX in the scripts discussed above. The location of X is classified as a state for X as a person, since this is meaningless in the absence of X, and the destination floor of X is classified as a state for X in the role of lift user, since this is meaningless outside this role. Whether or not X is currently playing the liftuser role is reflected in the boolean value of the special observable LIVEliftuser[X], which is true or false according to the current value of loc[X]. As a lift user, X has access to certain observables as oracles, either in the sense that she can observe them directly, or that she can observe them at certain times, and may retain some notion of their current values.  She typically knows her destination floor. She also knows whether she is in the lift, or at a floor, as determined by the oracle loc[X].  If X is in the lift, she has some notion of what floor the lift is currently at, as represented by the observable pos[X].  The observable pos[X] is classified as  a derivate because of the dependency that defines it in terms of the current lift position and the value of loc[X].  The observables over which X can conditionally exercise control are classified as handles: they include X's location and destination. The conditions under which X can redefine these observables are set out in her protocol. The two example privileges specified for X indicate that if X is in the lift, the lift is at her destination floor and the door is open, then X can step out of the lift, and that moreover X can change her mind about her destination floor at any time.

An LSD account is not in general to be interpreted as a specification, but rather as documenting the characteristics of observables as they are experienced by the modeller in the real situation, and (if the EM model is sufficiently convincing) as they are experienced in the associated EM model. In effect, an LSD account is intended to complement an artefact with which the modeller can interact, and is not to be viewed as an alternative form of representation. An LSD account can play a significant role in guiding the development of several different kinds of EM model for a multi-agent system such as a lift. For instance:

- It can be seen as describing the system as viewed from the perspectives of its various users . These views can then supply the basis for a distributed EM model in which the personal construal of each agent  is modelled as a client in a client-server configuration, and the corporate behaviour of the agents is developed by managing their interaction via the server. For instance, using a distributed variant of the EDEN interpreter, it would be possible to set up an EM model similar to that depicted in Figure 2 on a server, and to create EM models on four clients to recreate the interaction of the lift users X, Y, Z and I in the scenario as it appears from their four different perspectives. In such a model, there will be nothing that corresponds to the  lift users X, Y and I from the perspective of user Z, since Z merely presses the call button on floor 3 then descends to floor 2. The models for X, Y and I will be based on different variants of the prototypical lift user account given above. For instance, the oracles dest[X], dest[Y] and dest[I] have to be construed quite differently: user X has a correct perception that dest[X] is 4, but (when encouraged by I), supposes that pos[X] is 4 when it is in fact 3; user Y has an oracle to dest[X] which takes its value from the floor on which X gets out, and interprets dest[Y] as a derivate defined by dest[X]+1; user I has the number of the top floor of the building as an additional observable topfloor and  interprets the oracle dest[I] as a derivate defined by topfloor. A distributed model of this nature can provide a more vivid reconstruction of a scenario than the basic EM model depicted in Figure 2, as has been illustrated elsewhere in the reconstruction of historic railway accident developed by Sun in 1999 [].  

- It can be used in analysing the stimulus-response behaviour of automatic agents as they are construed to respond and act upon observables in their environment. Activity of this nature has a fundamental role in experimental science. It is also an important aspect of reactive systems development, where it is associated with the exploration and specification of context that precedes the design of control software. In applying EM principles to such activities, the most significant feature is making the connection between model-building from a personal subjective perspective and  what is interpreted as objective observation of a system by an external observer. A full discussion of the technical issues involved is beyond the scope of this paper - it has been one of the primary concerns of the EM project as a whole (cf. [Concurrent Systems Spec, Concurrent Engineering, Formal Spec from an OO perspective, Sun's thesis]). The basic concept is that of treating the activity of automatic agents as it were being carried out by a human agent with the appropriate perceptions and state-changing capabilities. By way of illustration, the lift system can be viewed as automatically carrying out the sequences of redefinitions required to reset the call buttons and open and close the doors on visiting a floor to which it is called. The stimulus for this operation is the presence of the lift car at a floor that is associated with a selected call button. An LSD account of this role of the lift system would (for instance) identify oracles - such as the status of call buttons, handles - such as the status of the doors, and include an action to manipulate the doors and call buttons appropriately in its protocol. A similar analysis can be used to develop a protocol to prescribe the motion of the lift. The EDEN interpreter includes features, such as procedures that are triggered by changes to specified observables, that can be introduced into the EM model of the lift to automate the lift system protocols. Such features make it possible to implement a lift simulation through an incremental process of extending the EM model in which the modeller's role involves shaping the behaviour to accord with realistic observation and interaction. The delay after which the doors close can be adjusted, for instance, and the selection of buttons by lift users simulated by direct mouse actions. The significant point here is that the LSD account has no formal operational semantics, but documents actual interaction with a computer-based artefact for which behaviours can be developed in much the same incremental and empirical fashion that an engineer might construct a protoype. In this process of empirical refinement of the EM model, the scope for extension is open: simple extensions that implement a lift scheduling algorithm, and introduce prototypical users based on the LSD account in Listing 1 can be found in the EM repository [EMrep: liftBeynon2003]. Further extensions for this model might involve introducing greater physical realism by way of modelling lift car velocity and acceleration, adding 3-dimensional visualisation, or linking the model to special-purpose hardware that could simulate the affect upon the user of forces generated by the lift motion.

The above account and illustration of EM serves to set the scene for the discussion of Radical Empiricism that follows. To fully appreciate this discussion, it is most helpful to have some experience of the nature of EM as a practical activity. Without such experience, it is difficult to appreciate the conceptual distinction between traditional computer programs and EM models that is described in section 1.1. It is in particular important to realise that all the lift models discussed in this section are to be regarded as part of a single open-ended conceptual process of exploration that can be seen as resembling the exploration of a city. Each model is informally associated with a particular way of viewing a lift situation and of organising the transitions between one situation and the next, but each is apprehended - even when, left to itself, it is executing a particular pattern of behaviour - state-by-state, in such a way that the modeller can choose to intervene to redirect the experience perhaps with a view to its reinterpretation. In this respect, the individuality of the different lift models is not defined objectively, but only with reference to what experiences are coherent for the individual modeller.
---------------------------------------------

2. Radical Empiricism - William James

William James's Essays in Radical Empiricism [] was first published in 1912. The potential relevance of James's 'philosophic attiitude' to a discussion of alternatives to a logicist framework for knowledge representation is apparent throughout these essays. In 'The World of Pure Experience', for instance, when discussing the philosophic atmosphere of his time, James refers to 'a feeling that [the extant school-solutions] are too abstract and academic', and goes on to write: 'Life is confused and superabundant, and what the younger generation appears to crave is more of the temperament of life in its philosophy, even though it were at some cost of logical rigor and of formal purity'. Empirical Modelling is motivated by a perceived need to develop methods of computer-based modelling that can do more justice to life in its confusion and superabundance than can the rational formal accounts of agent interaction that underlie typical computer programs. The distinction between these different views of human agency has been illustrated above when contrasting the farcical scenario of lift use associated with Box 1 with the prosaic and predictable behaviour that is attributed to prototypical lift users in Listing 1. This section explores other respects in which  the principles and techniques of EM can be related to thinking developed by James  in []. Our overall aim is to make it plausible that James's philosophical stance supplies a foundational framework in which to examine issues that seem paradoxical from more conventional philosophical perspectives.  [Not  yet a detailed and convincing exposition.] 

2.1. Philosophical foundations for EM

Some background motivation for our discussion can be found by thinking in general terms about what kind of philosophical foundations are appropriate for EM. One of the most characteristic activities in EM is the construction of a computer-based artefact (for instance, the lift model in Figure 2) that embodies patterns of observables, dependencies and agency that can be identified in an external situation to which the artefact refers (for instance, the specific use of the actual lift described in the scenario in Box 1). From a traditional computer science viewpoint, where there is an underlying presumption that all computer-based modelling can be accounted for by using the universal abstractions that rest ultimately upon the classical theory of computation, it is usual to propose that EM reduces to classical programming through a correspondence of the following general kind: an observable is a procedural variable, a dependency is a constraint relation [], an agent is a sophisticated abstraction such as an active object [].  The renunciation of each of these proposed reductions has been the focus of special attention in our previous work (see for instance: the discussion of variables in [Variables in Math and CS], of constraints in [Jaratsri Chapter 2?] and of agency in [founds of AI]). Broadly, our counter to this suggestion is similar in all three cases: that the notion of 'observable' refers to a feature of a situation that is experienced as having an identity and current status or value; that a 'dependency' is more than a perceived abstract relationship between values of variables and expresses the modeller's expectations about the immediate consequences of changing the values of observables in a situation; that 'agency' entails a potential for action that is of a truly experimental character, in that the possibility of taking the action has not been preconceived, and that no prior commitment to the possible interpretation of its consequences has been made. What links each of these counterproposals is the context in which our interaction with the computer model is conceived to be occurring: a context resembling that through which I as-of-now experience the city of Coventry through the sight of my neighbour's house and the sound of his lawnmower.

Our rejection of a conventional interpretation for EM has another significant element that is closely linked to Brian Cantwell Smith's critique of classical computational semantics in []. The proposed reduction of an EM model to a classical program purports to attribute an abstract behaviour to the EM model, in accordance with the ways in which variables, constraints and active objects might be used to specify behaviours in a conventional approach to model-building. The development of an EM model does not rely upon the identification of an abstract behaviour that can be embedded into the environment through formal symbolic associations. This is to revisit our previous observation, that an EM model does not in the first instance specify an activity, like travelling about a city using the underground, for which - thanks to the traveller's training in symbol recognition, and the careful engineering and signposting of the underground environment - limited experience of the city is required. On the contrary, the EM model offers itself to the modeller as a state to be experienced, where the correspondence between the features of the model and those of its referent are to be directly established, explored and enhanced through interaction. This perspective has to be understood with reference to a philosophical position that assumes no given absolute knowledge, in the same spirit that (in my current context) I cannot be absolutely sure that all I remember of the city of Coventry will be there to experience when I set off to visit the railway station.

As Cantwell Smith observes in [The Founds of Comp], the inadequacy of the classical view of computation is conspicuously exposed in emerging computing practice. The wide range of applications for EM principles that we have identified  to date highlights both the potential of EM and the challenge of understanding its semantics. The pragmatic view of the semantics of modelling 'real-world objects' that serves well enough in traditional engineering design can to some extent be adapted to an exercise such as using EM to model an actual lift. The concept of a direct correspondence between experience of an EM model and the experience of the real-world situation it represents requires more justification when the EM model is a spreadsheet, and the situation a financial scenario. It is also more difficult to argue for a direct correspondence between observables for an EM model to represent a lift that is under design and has yet to be built. Further complications arise if we consider the status of the EM model of a lift that we might create in a virtual reality, where the relationships between observables are no longer subject to familiar physical laws and constraints. EM has been used to build models that have the experiential characteristics of the data structures (such as the heap) that lie behind standard algorithms (such as heapsort), and thereby generate an environment in which to explore the design of algorithms [].  In other contexts, it is apparent that the use of EM principles is not directly concerned with issues of external representation. For instance, our tools now enable us to design new definitive notations - in particular, for graphics - within the same paradigm that we use to construct models, and - for such a notation - successful design is concerned with how the syntax of the new notation affects the correspondence between the structure of a script and the graphical image that it produces on the computer screen.

A feature common to all these applications of EM is the construction of a computer-based artefact that in some respects has the qualities of an instrument (cf []). The term 'instrument' is used here to express the idea that there is a reliable correlation between the interactions of the modeller with artefact and its associated changes of state. This correlation may be explicitly engineered by the modeller, or learned through skill acquired in mastery of the instrument. Explicit engineering is prominent in the case of a financial instrument such as spreadsheet, where the definitions of cells are contrived to express known relationships between observables. Skilful interaction is more prominent in relation to a musical instrument, such as the violin, where the tiniest nuances in the movement of the bow can be used to control the sound generated. In broad terms, the account of EM that we have sought to develop in our project represents EM models as instruments simultaneously under development and in use by the modeller, in which both explicit engineering and skilful interaction have a role to play. Through explicit formulation of dependencies and through experimental redefinition, the modeller develops an understanding of how interactions with an EM model reliably effect changes to its state. In this account of EM, the interaction with the instrument does not acquire meaning as a result of a complex abstract process of off-line decoding; it directly evokes a parallel experience because of the perceived similarity between the effects of interaction with the instrument and the familiar effects of interaction in another context. It is in just this manner that the movement of geometric elements of the simple drawing in Figure 2 evokes familiar interactions with an actual lift.

The correspondence between one experience and another that underpins EM is different in character from the 'similarity between behaviours' or 'similarity in static appearance' that is commonplace in routine prototyping of software and engineering systems. As the lift model illustrates, EM can serve to establish such similarities, but the connection beween an EM model and the situation to which it refers has a deeper significance. The correspondence between interactions with the EM model and interactions with its referent is itself a matter of immediate experience, subject to confirmation, exploration or possibly even refutation by the modeller 'as of now'.  A correspondence of this nature is rooted in the notions of 'observable', 'dependency' and 'agency' as they have been discussed above: it has a concrete and dynamic rather than abstract and static quality. In immediate experience, the agency of the modeller has the capacity to confirm or confound expectations, to create or destroy observables, to make or break dependencies. In these respects, it resembles the agency of the experimental scientist, whose actions can be used to test her construal.

The potential role that language and symbolic conventions can play in this context is a delicate issue. It is self-evident that our apprehension of correspondences in immediate experience can be mediated by language, as when we respond to the value in the column of the spreadsheet that is headed 'balance' or 'profit'. It is quite another matter to argue - as some philosophical traditions appear to do - that language plays an essential role in all correspondences between experiences. A core idea in EM is that not all correspondences between one experience and another can be established by symbolic conventions - at some level, correspondences must be made through direct experience without reference to language. The expectations of the experimental scientist may well entail much sophisticated theory, but the primitive correspondences that provide the grounding for such theory are arguably beyond words and equations. Experience in applying EM principles and tools suggest the further hypothesis that agency, dependency and observation have a fundamental role in such primitive correspondences.

2.2. Radical Empiricism 

Experience of EM, and reflection about its semantics, endorses a philosophical position that has strong points of connection with William James's Radical Empiricism. The primitive correspondences between experiences at the core of EM are necessarily personal experiences, and in the first instance are associated with subjective and provisional knowledge. This establishes priorities that are in line with those of RE: to account for logic and theory in terms of observation and experiment, rather than to account for observation and experiment in terms of logic and theory. Practical experience of EM reinforces this perspective, demonstrating how EM can be accompanied by transitions from personal to public, subjective to objective, and provisional to assured. This section discusses how some key ideas of RE are helpful in elaborating on what is involved in EM.


Motivation
	- understanding better what is meant by dependency ('indivisible' connections between state changes)
	- appreciation that many issues that seem prima facie to be satisfactorily accounted for become problematic in a VR context
	- giving an account that begins with personal experience and deals subsequently with objective knowledge etc
	
linking modelling with definitive scripts to the categories of experience referenced by WJ (cf Jaratsri's thesis)

'tracking WJ's exposition of the empirical roots of knowledge'


----------------------
Doppelganger

locS is if locX==0 then 6 - _liftfloor else (if locX == 7 then 7 else 6 - locX)

Useful for purposes of discussion of knowledge: extraneous hypothesis untestable without cooperation of other users: highlight the idea of construal


a. Conjunctive relations

In [], James remarks that, in RE, "the relations that connect experiences must themselves be experienced relations, and any kind of relation experienced must be accounted as 'real' as anything else in the system". One of his primary concerns is that traditional empiricists emphasise the disjunction in experience "leaving things permanently disjoined", whilst the rationalists remedy this disjunction "by their Absolutes ..., or whatever other fictitious agencies of union they may have employed".  For James, both conjunctive and disjunctive relations should be deemed to be given in experience. Amongst these, he includes "the most intimate of conjunctive relations, the passing of one experience into another when they belong to the same self ".

James's outlook helps to explain the difficulty we have encountered in understanding and communicating the nature of EM models. The typical computer scientist has a natural desire to attribute a characteristic set of discrete states and behaviours to the EM model of the lift in Figure 1, and to view it as a structure or system. In the mind of the modeller, the character of the EM model is more elusive. We can experience the state of the lift model as it is depicted in Figure 1, but interpret this in relation to all the other experiences of the states that have brought the model to this point. By the same token, what we experience in the current state of the model stands in an open, yet to be explored, relation to other experiences we can get by interacting with the model. What we understand by the model is an unfolding conjunction of experiences that cannot be circumscribed but is apprehended as a single relation.

An important aspect of James's analysis is the emphasis it places on the state of mind of the observer, dispensing with the 'reality of the given world' as the primary source of knowledge. In observing the development of the EM model of the lift, we are led to think quite as much about the evolving state of mind of the modeller as about realistic changes to the state of the actual lift, whether these take the form of a movement from one floor to the next, or adding labels to the call buttons in the lift car. This is keeping with our perception in EM that, contrary to the received view that a computer model of lift should only - perhaps even can only - be constructed with a specific goal and behaviour in mind, our EM model of the lift is somewhat neutral to purpose. Certainly, the experiences of the lift model that would be generated through the interaction of modellers acting in the roles of lift users, lift designers, lift analysts, or story tellers would be quite different, and reflect many different kinds of conjunctive relation in their minds.

Of particular relevance to EM  is James's contention that "the first great pitfall from which [RE] will save us is an artifical conception of the relations between knower and known" [].  This issue relates directly to the discussion above concerning how correspondences between experiences are established. The artificiality to which James alludes here stems from what is perceived by other philosophers as the 'indefeasibly dualistic' structure of experience [Does C Exist?]. For James, there is no such duality: "All the while, in the very bosom of the finite experience, every conjunction required to make the relation intelligible is given in full" [].

James's philosophical position is helpful in understanding the nature of EM. As has been argued above, the fact that the EM model of a lift stands in a special relation to an actual lift (viz. in what James characterises as 'the relation between knower and known' []) is not illuminated by classifying the one as a 'mental model' and the other as a 'real-world object'. What matters is that they are two portions of experience that are related in a way that is itself experienced by the modeller (cf [Does C Exist?]). This leads us to a characterisation of the modeller that matches our experience of EM activity well: that of an agent who generates an experience that knows another. In the same spirit, EM principles and tools can be seen as assisting the generation of this experience.  In this context, our choice of the word 'model' belies our faithfulness to James's account of knowing, as it is commonly associated with what James rejects by way of "representative theories".

The simplicity of the relation of knowing, as James describes it, is consistent with our experience of how readily EM models can be combined and reinterpreted. James rejects the duplicity of experience that distinguishes 'consciousness' from 'content' : "Experience ... has no such inner duplicity; and the separation of it into consciousness and content comes, not by way of subtraction, but by way of addition - the addition, to a given concrete piece of it, of other sets of experiences, in connection with which severally its use or function may be of different kinds". This explanation accounts for the way in which the object of study in one exercise in EM seamlessly becomes a part of the EM model in another; for the fact that an EM artefact can be developed without a referent in mind, as can an artefact in bricolage; for the adjunction of the roofs?

juxtaposition of models as 'sense-making': constructing a model as something of experience in itself, to which something is added when taken in conjunction with another experience ... essence of the model semantics, feature of the addition of visualisation etc (cf James's comments on consciousness)

b. Agency and dependency

In EM, there is an intimate relationship between the notions of dependency and agency. Dependency is in effect a way of conceiving all the consequences that are an integral part of a single action. This image finds its practical realisation in EM models in the modelling with definitive scripts (cf []), where a typical atomic action takes the form of redefining an observable or introducing / removing a cluster of observables.

There is no explicit reference to dependency in James's account of pure experience. Amongst the conjunctive relations he lists "relations of activity, tying terms into series involving change, tendency, resistance and the causal order generally". One of the most significant features of EM is that it provides an alternative to the classical Von Neumann model of state, where the values of procedural variables are treated as discrete and independent: the dependencies in a script are not assertions about values alone, but embody expectations about responses to interaction that are themselves a part of state. To the extent that these expectations are relations between observables that are directly experienced, it seems appropriate to classify dependencies as conjunctive relations of activity. A plausible analogy likens the disjoint terms of traditional empiricism to the discrete variables of procedural programming, and the conjunctive relations of Radical Empiricism to the dependencies in modelling with definitive scripts. The elaborate programmng mechanisms that are required to maintain dependencies between procedural variables in a VN representation of state echo James's comment about the complex ways in which rationalists remedy disjunction.

<EM as suited to the investigation of construals> A common feature of EM is the manner in which the context for action, as established by the dependencies that prevail amongst observables, shapes its significance and interpretation. This is the mechanism that operates in Figure 1, where, in one context but not another, the movement of the lift entails the movement of a lift user. 

<where is the real activity - pertinent to the concept of construal>

continuous transition

problematic in the computer realisation - in the mind

ambiguity about what is substantive ('perching of the bird') and transitive ('flight of the bird'') in WJ's sense: "as if a differential quotient ... " - (cf procedural and definitive variables)

discrete jump that the lift makes as substitutes for the actual transition from one floor to the next subject to certain constraints on experience - cf the detective story in which we might well be asked to conceive that a person ascending in the lift from floor 3 does not arrive at floor 4, or the need the engineer may have to consider positions for _liftfloor other than exact floor positions

----------------

<manner in which James discusses transitions in experience is helpful in clarifying interactions in EM>

speaking of 'moving from one floor to the next' in relation to continuous lift motion

Discussion: The location of the lift user is to be thought of as defined by 'in the lift', 'on a particular floor' or 'not in the vicinity of the lift'. It is not to be identified with their actual physical location, but is nonetheless an observable feature of their location. Just exactly where the lift user is standing in or in the vicinity of the lift, or what posture they adopt, is not deemed significant. From these remarks, it is clear that the dependency by which "the position of the user is determined by that of the lift" is to be construed in a different way from the dependency that links the position of the lift car to that of the end of the supporting cable. The correlation between the movement of the end of the cable and that of the lift car is far more exact, and is easily interpreted with reference to atomic 'infinitessimal' change. Deeming the movement of the lift between one floor and the next (as modelled by _liftfloor++;) to be an atomic change reflects knowledge that "no matter what the lift user does" within the lift, there is no possibility that they will not be moved with the lift from one floor to the next. Note that

- The assumptions needed to justify the model relate to lifts as we experience them - they could be violated in a virtual reality or science fiction scenario.

- In the model in its current form, we observe the lift 'moving from floor to floor' rather the continuous motion of the lift between floors, so that the physical position of the lift car is seen as dependent on the current location of the lift as defined by the discrete-valued observable '_liftfloor'. We can adapt the model so that _liftfloor can assume fractional values, corresponding to the lift being at fractional positions, such a
	1, 1.1, 1.2, ... , 2, 2.1, 2.2, ..., 3, 3.1, ... etc
that designate positions at or between floors.
----------------------

can make sense out of the artefact by extracting groups of observables from the experience they provide and making sense of these - cf discussion of railway model and conceptual integrity in Allan's thesis

James's takes a pragmatic view about what 'the real agents' are - encouraging us not to seek absolute answers to such matters as attributing agency.

EM model as an environment in which to explore attributions of agency as 'possible
construals'

understanding 'agency' as more than any circumscribed preconceived rationalised interaction

views of agency as 'we are puppets' / 'we have free will' / 'our behaviour emerges from the agency of simpler components - cf. Society of Mind, neurons'

role that EM can play in modelling such views and their interrelationship

c. Knowledge and reality

The potentially purely subjective nature of the kinds of interaction with artefacts we can use to develop and reinforce our personal 'knowledge'

personal reality as authenticity of experience

The usefulness of distributed modelling in which there are shared observables, but negotiation of meaning plays an essential role

What is knowledge without the terminus? - cf the artefact pregnant with possible meanings but without conceptual integrity (cf railway model) - cf floor 4 of the lift scenario, where I am not tracing through to the inherent contradiction about which floor I'm at, which floor the lifts at - pragmatic resolution given constraints of time and inability to resolve problem abstractly

Knowledge as implicit and tacit in interaction with artefacts, as having an active and essentially dynamic nature - "Why insist that knowing is a static relation out of time when it practically seems so much a function of our active life? - WJ"

"To continue thinking unchallenged is ninety nine times out of a hundred, our practical substitute for knowing in the completed sense - WJ" - 

Discussion of relationship between interaction with artefacts and propositional knowledge (tacit/concrete, provisional, personal/private -> symbolic/abstract, certain, public) (cf Foundations of AI paper) 

Conclusion

Shouldn't venture 'experience management' without artefacts to represent experience.
Essential importance of the personal stream of thought, and direct experience.

References

EM and the foundations of AI

Gooding

William James

Blocks studies in logic

Formal Specification from an Observation-Oriented Perspective

Computer as Instrument

Dennett

Cantwell Smith

< must refer to definitive notations somewhere >

---------------------------------------------

"If from the top of a long cold barren hill I hear the distant whistle of a thrush which seems to come up from some warm woody shelter beyond the edge of the hill, this sound coming faint over the rocks with a mingled feeling of strangeness and joy, the idea of the place about me, and the imaginary one beyond will all be combined together in such a manner in my mind as to become inseparable." An Essay on the Principles of Human Action, William Hazlitt

reason is a "slow, inert, speculative, imperfect faculty"

Of Bentham: "They say he has been translated into French: he ought to be translated into English."

