'HE 1986 INTERNATIONAL CONFERENCE OF THE SYSTEM DINAMICS SOCIETY. SEVILLA, OCTOBER, 1986. 1.223
Development of a common communication and control system
for system dynamics type of simulation models
Prof. Dr. H. Krallmann
Dr. B. Rieger
Dipl.-Ing. G. Hentzelt
Abstract
Today for managers or in general for non data processing
experts the use and application of simulation models is of
very high expenditure.
Editing and changing model parameters, studying the simu-
lation language or applying e.g. a graphical standard soft-
ware package are very unusual activities for this special
user group. Due to this situation it cannot be expected that
simulation models which deliver very important results for
decision support get near to these people.
In this paper a user friendly communication and control
system is presented, which offers an optimal user guidance
in modifying and running simulation models, in creating a
user friendly graphical output and in the interpretation of
the model results.
1.224 — THE 1986 INTERNATIONAL CONFERENCE OF THE SYSTEM DINAMICS SOCIETY. SEVILLA, OCTOBER, 1986,
1. Introduction
Characteristics both internal and external to the firm, such
as sudden changes in environmental conditions or growing
complexity of decision determinants, increasingly put
Management under pressure. Lack of suitable resources
frequently compels reactive behaviour, whereby potentially
profitable opportunities are not noticed or trends en-
dangering the firm are recognized too late /KRALLMANN 81/.
Dynamic modeling is one of a number of tools to support
management in this area. There are three major problems,
that restrain simulation models from a widespread and direct
use by top management:
= the application of simulation packages
i the use of editors to change model parameters
od difficulties in model result interpretation
An easy to use communication and control system facing these
problems can be a powerful tool to improve the acceptance of
simulation models. The system presented in this paper in a
first step integrates the use of DYNAMO /PUGH 76/ as simula-
tion language with selected features of the statistical
analysis system SAS /SAS 83/ as tool for the graphical
representation of model results.
Since one major advantage of simulation models for manage-
ment decisions lies in its parametric use, whilst the models
themselves are still built by specialized staff personal,
the system primarily concentrates on functions applying
preformulated models.
Supplying these functions in a comfortable and easy to use
way including automatic and quick generation of high resolu-
tion graphics, expressive to typical managerial questions
such as "what if ?", the advantages of simulation models can
better be transferred. In this way, acceptance by top
management can be gained faster. This feeling for potential
benefits is considered as a prerequisite for a wide spread
and more direct use by managers /RIEGER 85/. Parallel to
this development more sophisticated functions’ concerning the
“BTa
T
werbeTq Tor3UCD weqsAs
Screen - Flow Diagram
Tend? Tmodel-menv lk
SMA-SMS models
o fneltremose! wr] sss [avo [on
sve istorng
‘rites
wwe detsaeay HL aedbinaand
eR interpretaon of
result withoas
ox documentation
on, ot medal function selection menu ie
END baekmard ump
562 backward sump v1 [aan [ene [oon [eno [ 3
a ralpscreed | C
storing- variables menu. results-interpretation-menu(variabies) = | oi [ short documentation
= target variables (1-4)
a wp]: om carat me
documentation menu
fog Hoon
er] mos var [ee 73
strategy-variables- menu rents ntrpretation-menu(atrategied
| raegy vara pretation menu rategies) Ce
7 ext select ategis
=] mare [ae |e mr Pas NRRSR |
model varabes
+ | aocumentavon >| documentston
next Text
page nage
staat
onan
“9861 ‘Y3GOL00 ‘VTUATS ‘ALIIOOS SOINYNIG W3LSAS 3H1.4O-3ONSY3INOO TWNOLLYNYALNI 986} SHI
Geek
1.226 THE 1986 INTERNATIONAL CONFERENCE OF THE SYSTEM DINAMICS SOCIETY. SEVILLA, OCTOBER, 1986.
structural modifications of models up to the formulation of
new models can be added to the system.
2. Requirements
Due to this strategy the functional requirements for the
first system version are the following /HENTZELT 85/:
Ss selection of preformulated simulation models
- generation cf alternatives by variation of model
variables representing the instruments of
managerial policy
- interactive initiation and automatic control of
simulation cycles including the storing and
administration of selected result parameters
- interactive selection of result parameters and
graphic processing for comparative analysis of
alternative strategies
- model documentation inquiries on different
levels of aggregation
po System User Communication
To fulfil these and later requirements the functions have
been aggregated to three logical blocks:
> Manipulation of simulation and model variables
and start of the simulation runs
- Selection of stored simulation runs to start
comparative plots
a Online documentation of the available models
The system user communication is controled by easy to use
screen menus. For each of the menus a help screen exists,
attainable with the permanent function key PF-1. The screen
menus are designed in a common manner, and functions as well
as function keys keep their meaning. The system is resistant
against wrong user input and only warning messages will be
displayed with a request for new input. An overview of the
system control is shown in fig. 1.
int 1980 INIERNAIIUNAL GUNFERENCE OF THE SYSTEM DINAMICS SOCIETY. SEVILLA, OCTOBER, 1986, 1.227
The first menu (fig. 2) shows the different models available
to the system. Model names are read from a directory file in
the model management system and displayed on the screen
mask. The user selects the desired model by a three letter
identification (SM1...SM5). The identification END or
depression of the permanent function key PF-3 ends the
session. The PF-1 key displays a short description of all
available models on the screen. Messages for the selection
of a non existing model or for a wrong function selection
are available.
c >
TU - BERLIN FG - SYSTEMANALYSE / EDV
oe MODELLAUSWAHL oo
BITTE WAEMLEN SLE =
> sas
M1: SIMULATIONSMODELL - Produktions- und Absatzstrategren -
SM2 : SIMULATIONSMODELL - Marketing - Mix - Strategien -
SM3: SIMULATIONSMODELL - Bestel ipolitik
SM4 : SIMULATIONSMODELL - Qualitative Personatplanung -
SMS: STMULATIONSMODELL NICHT IMPLEMENTIERT
ENO : ENDE
S-Quit
WEITER MIT CENTER>-TASTE >>>SIMULATIONSMODELL NOCH NICHT IMPLEMENTIERT<<<
Fig. 2 Model-Selection-Menu
The next screen (fig. 3) is the function-selection-menu. It
gives the opportunity to branch to the three major system
functions. In further releases functions for model building
will be added on this level. Function SIM passes control to
the screens for manipulation of simulation and model varia-
bles and start of model runs. ERG branches to the graphical
result interpretation. Selection of this function without
any result of model runs available causes an appropriate
1.228 THE 1986 INTERNATIONAL CONFERENCE OF THE SYSTEM DINAMICS SOCIETY. SEVILLA, OCTOBER, 1986.
warning message and request new function selection. DOK
branches to the online documentation function. END or PF-3
key branches back to the model menu. PF-1 key gives the
online description of available functions for this screen.
Other input is rejected with appropriate warning messages.
~
BERLE FG - SYSTEMANALYSE / OV
os FUNK TIONSAUSWAHL oe
WAEHLEN SIE ===> sim
SIM: SIMULATIONSLAUF STARTEN
ERG ; ERGEANISINTERPRETATION
DOK : OOKUMENTAT LON
ENO: ENDE
tsHelp
WEITER MET CENTER>-rASTE
a S)
Fig. 3 Function-Selection-Menu
3-1. Simulation Runs
This function combines all the steps necessary to start a
sequence of reruns and store the results for later compara-
tive plots. It consists of two screens requesting and
checking all needed parameters. To start simulation runs
using the simulation processor DYNAMO information is needed
about the control parameters LENGTH and SAVPER, describing
the simulation length and the interval of TIME between the
saving of results for later comparative plots. The communi-
cation system requests these parameters in the storage-
variables-menu (fig. 4). In order to get convenient results,
the system only allows input within bounds defined by the
THE 1986 INTERNATIONAL CONFERENCE OF THE SYSTEM DINAMICS SOCIETY. SEVILLA, OCTOBER, 1986, 1.229
model builder. Values outside these bounds are rejected and
are changed to a marginal value. A message is displayed to
attend to the online help available by the PF-1 key. The
according help screen displays the description of the
parameters and their value bounds as well as a short expla-
nation of the input functions for this screen. Function SVA
passes control to the strategy-variables-modificationmenu to
prepare the model for different runs. Function END or PF-3
key gives control back to the function-selection-menu.
a >)
TU - BERLIN FG - SYSTEMANALYSE / EDV
oe SPEITCHERVARTIABLEN oe
BITTE WAEHLEN SIE
> SvA
SVA : SPEICHERVARTABLEN SETZEN
END : ENDE
Simulat ionsdauer ses) | 120 | Monate
Speicherintervall a> | 6 | Monate.
WEITER MIT CENTERD-TASTE >>>PARAMETER GEAENDERT - HILFSMENUE BEACHTEN <<<
Fig. 4 Storage-Variables-Menu
The strategy-variables-modification-menu, shown in fig. 5,
allows the preparation of the model for up to 19 runs. They
can be compared in comparative high resolution graphs with
the result interpretation facility lateron. The system again
restricts variable modification to intervals defined by the
model builder. Meaningless values for these variables will
be rejected and values are changed. A message to attend to
the help screen is displayed. The system rejects more than
one run with the same combination of variable values with. an
1.230 THE 1986 INTERNATIONAL CONFERENCE OF THE SYSTEM DINAMICS SOCIETY. SEVILLA, OCTOBER, 1986.
( >
TU - BERLIN FG - SYSTEMANALYSE / €0V
Strategie Nr. 1
we STRATEGIEVARIABLEN — ¢¥0
BITTE WAEHLEN STE ===> ava
MVA ; STRATEGIEVARIABLEN SETZEN
END : EINGABEN BEENDEN
Bas iskapazitaet 12> | 100 | Moteren/Monat
Erastel lunges
10 | Personen/60 Monate
THe 1p
WEITER MIP CENTERD~ TASTE
+ TU - BERLIN FG SYSTEMANALYSE UND EOV +
‘ Setzen der Strategievariablen .
: MVA Steategievariablen setzea .
: END Eingaben beenden, :
: sinnvol ler Varvationsbere ich (ganzzahtig) *
: Basiskapazitaet 100 - 300 Motoren/Monat :
. Evastellungen . 0 - 70 Personen/60 Monate *
Es koennen bis zu 19 unterschiedliche Strategiekombi-
nationen der Variablen gesetzt werden, fuer die Simula~
: Lionslaeufe gestartet werden. Die Ergebaisvariablen koennea
. danach vergleichend graphisch dargestelit werden
5 Ti Die Strategievaciablen werden gegebenenfalls programm-
gestevert in den Grenzen korrigiert
Ne J
Fig. 5 Strategy-Variables-Modification-Menu
THE 1986 INTERNATIONAL CONFERENCE OF THE SYSTEM DINAMICS SOCIETY. SEVILLA, OCTOBER, 1986. 1.231
appropriate message. The input of MVA as selected function
indicates continuation of variable modification for further
runs, END indicates input termination and start of the
DYNAMO processor to the system. PF-3 key branches back to
the function-selection-menu.
3.2. Results Interpretation
After successful model runs the system comes back with the
function-selection-menu, allowing the user to view selected
results of the model runs in comparative plots by function
ERG in this menu. This causes a branch to the result-inter-
pretation-menu (fig. 6). Depending on the selected simulati-
on model the according target variables defined by the model
builder are displayed for selection. The user only has to
mark the desired one with an X or he can get further infor-
mation by PF-1. Additionally the output device, plotter or
terminal, can be chosen.
ry gen ro srsremmaurse sew
TeeERGEBNISINTER PRETATION t40
FUER DAS SIMULATIONSMODELL NR. 1
SIND LAEUFE MIT FOLGENDEN PARAMETERN GESPEICHERT:
Simulationsdauer 120 Monate
Speicheriatervall 6 Monate
BITTE EINE VARIABLE FUER VERGLEICHENDEN PLOT ANKREUZEN
Marktantei! x
Istlieferzeit
Absatz
Betriebsergebnis
TERMINAL P: PLOTTER
BITTE WAEHLEN SIE ===> T
1=Heip S-quit
WEITER MIT CENTERD-TASTE
Fig. 6 Results-Interpretation-Menu
1.232 THE 1986 INTERNATIONAL CONFERENCE OF THE SYSTEM DINAMICS SOCIETY. SEVILLA, OCTOBER, 1986.
The next screen presented is the menu for model run
selection (fig. 7). In this screen all stored reruns are
displayed with the corresponding values of the strategy
variables. If the user defined more than ten runs in the
modification menu, the rest is displayed on a second screen
accessible by next page function. The desired model runs for
comparative plots can be marked in this menu.
sen £6 = SYSTEMAMALYSE 7 €0V )
SEITE NR. 1
HT ERGEBNISTNTERPRETATION te
FUER OIE YARTABLE Marktantei!
KAEUZEN SIE BITTE CIE 2U VERGLEICHENDEN STRATEGIEN AN (MAX. 5)
STRAT. Basiskapacitaet Einstel Tungen
1 100 an
2 100 30 |
3 190 70 x
4 200 4 x
3200 30
8 200 70 x
7 300 0
3 300 10
9 300 20 |
10300 30
BLAETTERN (J/N) =
IeHelp
WEITER MIT CENTERD-TASTE
L J
Fig. 7 Model-Run~Selection-Menu
No CPLOT card has to be typed by the user. It will be
generated automatically by the system according to the
user's selections. The system either sets up a SAS-graph job
for the plotting device to produce a hard copy or starts the
SAS-graphic processor to display the comparative plots on
the screen (fig. 8). The selection of
results-interpretation-menu is displayed again for further
plots. PF-1 key displays help for these menus, PF-3 branches
back to function-selection-menu from both of them.
TIE TWI90 INTERNA TIONAL VONFERENGE UF THE SYSTEM DINAMICS SOCIETY. SEVILLA, OCTOBER, 1986. 1.233
Fig. 8 Example of Generated Comparative Plot
3.3. Model Documentation
The third function accessible from function-selection-menu
is the online documentation of the simulation model and its
variables. It is subdivided into three dynamically filled
screens in order to supply information on different levels
of aggregation. The first screen of this function (fig. 9)
shows a short model description. Then the user can decide
whether he needs general model information (function MOB) or
information about the action and target variables (function
VAR) (fig. 10). The system will display the desired docu-
mentation and show up with this menu again. END or PF-3 key
branches back to main functions menu, PF-1 explains the use
of this screen.
1.234 THE 1986 INTERNATIONAL CONFERENCE OF THE SYSTEM DINAMICS SOCIETY. SEVILLA, OCTOBER, 1986.
(~ >)
KURLSESCHREIBUNG
GM + SIMULATIONSMODELL
+ ay vorliegende Dynamo-Simulatronsmode?] zur Entwicklung .
+ kaordimierter Peogukt ions und Absatzstrategten fuer :
+ Grossmotarenharstellec wurde vm Hinblick auf folgende ‘
+ Tielsersungen erste!) :
+ + Peognose ser Nachfrageentwickiung nach den verschiedenen —¢
+ Motortypen :
+ + Abbilaung der Kaufentschetdungsfaktoren mit unternenme- :
+ riscnen Stevermoegl ichke! ten: 2
+ Abbi Tdung des Produkt ronsvereiches mit guenstigstmoegli- — *
+ cher Disposition und Ha!bfertigprodukt ionsplanung ,
WELTER MIT CENTERD-TASTE
Fig. 9 Short Model Documentation
aenuin £5 = SisTeManaLyst”/ ov )
BITE WAEHLEN STE =
Help
WEITER MIT CENTERD-TASTE
MOB : MODELL — BESCHRELBUNG
VAR : VARIABLEN BESCHREIBUNG
ENO: ENDE
Fig.
10 Documentation Menu
Int 1¥00 INIEKNATIUNAL CONFERENCE OF THE SYSTEM DINAMICS SOCIETY. SEVILLA, OCTOBER, 1986. 1.235.
4. Conclusions
The presented communication and control system has been
tested with several applications in practice. The improved
acceptance and gained success documents both the potential
benefit of System Dynamics models for decision support in
management and the gap between methodological power and
practical use. However the presented system is only a first
step into the direction of bringing data processing, or
simulation modeling in special, nearer to the management.
For the conception of the system very much effort was spent
to keep the system independent of the simulation package
used in it. The demand for a documentation of the models by
the system keeps good models in use, because the contents of
the model will not get lost. By modularisation of the system
it is adaptable for other simulation languages and graphical
output packages than those used in the system. However these
packages should give the opportunity of bringing in other
functions than those used in the system at present. With
regard to sensitivity analysis, graphical or tabular presen-
tation of target variables against strategy variables
(instead of TIME) are of great interest. A prototype soluti-
on has already been realized by the integration of another
software package. A further step on the systems development
is an interactive support by formulating simulation models
of the system dynamics type. For this type of simulation
models a graphical definition tool could be considered. This
might be especially useful as an education facility for
simulation modeling on personal computers.
4.236 THE 1986 INTERNATIONAL CONFERENCE OF THE SYSTEM DINAMICS SOCIETY. SEVILLA, OCTOBER, 1986.
/HENTZELT 85/
/KRALLMANN 81/
/PUGH 76/
/RIEGER 85/
/SAS 83/
References
Hentzelt, G.: Konzeption und Implementierung
eines Entscheidungsunterstiitzungssystems zur
Planung koordinierter Unternehmensstrategien.
Diplomarbeit, TU Berlin, 1985.
Krallmann, H.: Strategische Entscheidungs-
unterstlitzungssysteme im Unternehmen.
In: Bergner (Hrsg.): Planung und Rechnungs-
wesen in der BWL. Berlin, 1981.
Pugh, A. L.: Dynamo User's Manual.
Cambridge (Mass.), 1976.
Rieger, B.: Leistungsfahigkeit von Entschei-
dungsunterstiitzungssystemen im Unternehmen -
dargestellt am Beispiel der Preisgestaltung
von Mehrproduktunternehmen.
Dissertation, TU Berlin, 1985.
SAS Institute: SAS / Graph User's Guide.
cary (NC.), 1983.
CC BY-NC-SA 4.0