Hi Peer-Olaf,
First of all, I think the research question in your post, which I think
is a bit ill-structured, makes the necessity of answering the "Why
ABS?" question redundant. In the way, you have expressed the question,
it sounds more like a methodological research aiming to explore the
potential benefits of using ABS. Hence, the answer to the "Why ABS?"
question seems apparent in the research question; because you want to
learn if ABS helps you, or not.
Anyway, I guess I can safely assume that your main concern is not
exploring the potential of a specific approach (ie ABS), but studying
the impact of certain policies of HRM practices on customer
satisfaction, and in order to do so you wish to utilize a
simulation-based approach.
I think answering a question like "Why ABS/DES/SD is good for this
study?" relies on the matching two basic things. One of them is about
what that modeling paradigm can offer, for what kind of systems the
representation possible with that paradigm is more powerful, etc. I
believe this mail-list is full of people who can provide in-depth
insights about this aspect of ABS/ABMs.
The second important point is the way you conceptualize the system.
Considering that you will be studying the temporal behavior of system
regarding customer satisfaction, there is an abstraction of the way
components in the Human resources system interact and yield observed
customer satisfaction levels. I would call this researcher's hypothesis
about the dynamic behavior of the system.
I believe answering "Why X?" question shall rely on the degree of fit
between these two aspects; the researcher's hypothesis and what X can
offer in terms of representation capabilities.
For example, if I know/believe/assume that the workers are heterogeneous
in the sense they respond under different situations, and their actions
are strongly influenced by their interactions with a subset of the
workers (their immediate colleagues), I may argue that ABM provides a
much efficient 'language' to formalize this hypothesis.
On the other hand, if I know/believe/assume that the workers are still
heterogeneous, but their actions are mainly driven not by their
interactions with others, but by environmental factors as salary
increase, customer density, working hours, etc. Apart from that I may
also assume that environmental conditions are dependent on worker
actions, hence forming some feedback with embedded time delays (eg
better worker performance, increased customer satisfaction, increased
number of customers, increased workload per worker, worsening worker
performance). If this is the case, SD may provide a more efficient
language in formalizing and analyzing this system.
Although this sounds extremely intuitive, in practice as far as I can
see, it does not work that way. Generally, we consciously or
unconsciously make our choice about the modeling paradigm before clearly
building our hypothesis about the system. After choosing the paradigm,
we then build a hypothesis that fits very well with the chosen paradigm.
The famous hammer-nail story...
This is also partly a consequence of the 'professional mental
deformation', I believe. After spending so much time with SD models, you
start to see feedback loops as the source of problem everywhere. Same
holds for ABMs.
Although not referring to your specific questions about the DES-ABM
comparison, I hope this adds some material for discussion.
Regards,
Gonenc
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Gonenc YUCEL
PhD Researcher, Policy Analysis Section
Faculty of Technology, Policy & Management
TU Delft
Jaffalaan 5, 2628BX, Delft
Room #: b.3.280
Phone #: +31-15-278 1702
Fax #: +31-15-278 6233
http://homepages.ipact.nl/~gyucel/
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> -----Original Message-----
> From: News and discussion about computer simulation in the social
sciences
> [mailto:[log in to unmask]] On Behalf Of Peer-Olaf Siebers
> Sent: Thursday, April 10, 2008 12:20 AM
> To: [log in to unmask]
> Subject: [SIMSOC] Difference between DES and ABS - is there one or
does it just
> depend on the world view?
>
> Hello
>
> I'm currently investigating the research question: Can Agent-Based
> Simulation (ABS) help us with assessing the impact of human resource
> management practices on customer satisfaction and the performance of
> service-oriented retail organisations?
>
> I have often been asked the following questions after presenting my
work:
> - Why do you use ABS?
> - Why can't you do it with Discrete Event Simulation (DES)?
> - Or do you use the agent approach just as a mindset rather than a
technique?
>
> Regarding these questions I never came to a satisfying conclusion! I
thought
> it would be interesting to collect the different views that people
have
> about this question, so I would like to discuss it here!
>
> The questions are:
> - What is the difference between ABS and DES?
> - Why do we use Agent-Based Modelling (ABM) and ABS?
>
> I have the feeling that very often people mix up terminology.
Therefore, I
> would like to sketch out how I understand the different terms:
>
> There are two simulation technologies:
> - Continuous Simulation
> - Discrete (Event?) Simulation
>
> There are three different paradigms (are these modelling paradigms?)
> - System Dynamics (SD) paradigm
> - Discrete Event (DE) paradigm
> - Agent Based (AB) paradigm
>
> For human-centred systems, when it is important to consider a
heterogeneous
> population, the AB paradigm seems to be the most useful approach to
use for
> the modelling process. There is a structural correspondence between
the real
> system and the model representation, which makes them more intuitive
and
> easier to understand.
>
> How do we actually (technically) implement an ABM?
>
> There are three different world views (approaches) for DES. The
different
> simulation systems provide facilities for model implementation
according to
> the world view. The three approaches are:
> - Activity Scanning
> - Event Scheduling (most frequently associated with the phrase DES)
> - Process Interaction
>
> Garrido (2001, p59) defines the Process Interaction World View as
follows:
> "In the process world view, the behaviour of the system under study is
> represented by a set of interacting processes. Recall that a process
is
> defined as a set of abstract data structures and the sequence of
operations
> carried out by an entity during its life within the system. The
merging of
> the event sequences of these processes contains all events that occur
in the
> system."
>
> For me, this sounds very much like a definition for ABS. So we use the
AB
> paradigm to develop our conceptual ideas and models (ABM) and then the
DES
> process interaction approach (which we call ABS) to implement the
models.
>
> Are there other ways to implement ABS models? Or is ABS just a buzz
word? Is
> it just a consequence that if you want to implement ABMs you want to
use an
> AB technology, hence a new name for an old method?
>
> Thanks for reading - I'm looking forward to hearing your comments!
>
>
>
> If you're interested in the project you can find more information and
> publications at http://www.cs.nott.ac.uk/~pos
>
>
>
> Definitions:
> - A technology is a manner of accomplishing a task especially using
> technical processes, methods, or knowledge (Merriam-Webster Online
> Dictionary: http://mw4.m-w.com/dictionary/technology).
>
> - A paradigm is a philosophical and theoretical framework of a
scientific
> school or discipline within which theories, laws, and generalizations
and
> the experiments performed in support of them are formulated
(Merriam-Webster
> Online Dictionary: http://mw4.m-w.com/dictionary/paradigm).
>
> - A worldview is a comprehensive conception or apprehension of the
world
> especially from a specific standpoint (Merriam-Webster Online
Dictionary:
> http://mw4.m-w.com/dictionary/weltanschauung).
>
>
>
> Reference:
> - J.M. Garrido (2001). Object-Oriented Discrete-Event Simulation with
Java:
> A practical introduction. Kluwer Academic: NY
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