=Paper=
{{Paper
|id=Vol-2348/short09
|storemode=property
|title=Multi-Project Sequencing in the Retail Sector
|pdfUrl=https://ceur-ws.org/Vol-2348/short09.pdf
|volume=Vol-2348
|authors=Semih-Eren Karakilic,Declan O Connor,Andreas Thümmel
|dblpUrl=https://dblp.org/rec/conf/cerc/KarakilicCT19
}}
==Multi-Project Sequencing in the Retail Sector==
https://ceur-ws.org/Vol-2348/short09.pdf
Business and Society
Multi-project sequencing in the retail sector
Semih-Eren Karakilic1[Prof. Dr. Declan O Connor - Prof. Dr. Andreas Thümmel]
1University of Applied Sciences Darmstadt, Schöfferstr. 3, 64295 Darmstadt, Germany
Abstract. In the age of digitalization, the importance of automating internal busi-
ness processes is increasing. A parallel event is the increase number of projects
and their complexity.
Mathematical methods from the field of operation research can be used to deter-
mine the optimal sequencing in order to minimize the loss of benefit. And con-
sequently, the optimal sequencing of the projects is sought, which maximizes the
overall contribution margin.
The sequencing of the projects determines the total contribution to margin after
the project is complete. Therefore, sequencing is of great importance for the com-
pany. Sequencing is currently performed manually but due to the number and
complexity of the projects optimal solutions can no longer be guaranteed using
manual sequencing. As a result, the company suffers a loss of benefit. The loss
of added value is the difference between the maximum achievable total contribu-
tion margin and the actual total contribution margin achieved.
Keywords: Multi-project, Sequencing, Optimization.
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Business and Society
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1 The planning and problems of sequencing multi-projects A
Subsection Sample
1.1. Sequencing requirements
A prerequisite for successful business management is planning. Complex relation-ships
are systematically worked through and summarized. This summary contains in-for-
mation about the consequences and effects of a decision. It is important to design this
planning holistically. Underlying this should be thought processes and coordination.
An important aspect in planning is the database. Good planning requires important in-
formation. The quality of the information has an influence on the deviation of the target
from the actual state [1]. Only when the data has been collected post project can it be
determined whether the problem was solved in the planned manner. The required data
may be insufficient.
The planning of projects can be summarized in the form of a business case. The busi-
ness case is the profitability analysis for the execution of the project [2]. This contains
target information, action alternatives and economic consequence [3].
First, the foundations for a project are in detail. These include a project description with
an economic goal. The benefit and the expected total costs should be easily calculable.
By comparing the key figures, the company can make a decision. In addition to deci-
sion-making, a business case is used for investment planning. In a business case, not
only financial aspects are considered. The risks and in particular the strategic economic
basis of the enterprise is an important factor for decision-making [4].
In multi-project planning, it is decided which projects will be implemented in the spec-
ified time. The business cases support the decision making process. Projects are as-
signed priorities. On this basis, the company processes the projects. Through the im-
plementation of the projects, the company expects a contribution margin as a benefit.
In order to minimize the loss of benefit and to determine the optimal sequencing, math-
ematical methods from the field of operation research can be used as a basis. Conse-
quently, the optimal sequencing of the projects is sought, which maximizes the overall
contribution to margin.
1.2. Definition of a Job
A project is a realization of a goal-oriented and time-limited undertaking. Project teams
implement projects. Projects consist of several partial work steps, which can be carried
out by several departments. As the result of a realized project, the company expects
both economic and other benefits.
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There may be projects that cost more money than they bring in. These projects could
be triggered externally. An example would be the enactment of new laws by of the
state. These projects are unavoidable for the company and must be implemented within
the specified period. In addition to external influences, projects can be triggered inter-
nally, e.g. by changing system processes or software [5].
1.3. Controlling and adopting the characteristics of projects for sequencing
Planning itself is not enough. In order to ensure that the actual values correspond to the
forecast values, activities must be monitored and controlled [6].
In project control, projects are evaluated using their parameters. The evaluation checks
whether the project goals can be achieved. Typical evaluations are plan/actual compar-
isons. The evaluations must be monitored and evaluated at regular intervals. In order to
detect deviations at an early stage and to initiate countermeasures, the observation times
must be as small as possible. On the other hand, this leads to a greater control effort [7].
The observation times can take the form of milestones and strategic monitoring. Thus,
standardization procedures can be implemented within the company [8].
The early detection of these risks enables control measures to be taken. The purpose of
the control system is to minimize or eliminate the deviation from the planned project.
If the deviation is too large, the countermeasure results in a new planning of the project.
A new planning can also have other reasons. For example, it may be due to limited
resources. Early recording and analysis of plan deviations shows the deviating devel-
opment [9].
On this basis, the countermeasures are specified in concrete terms. Deviations cannot
be avoided. The plan and the target comparison lead to new experiences. The experi-
ence can be used for future planning in the form of better forecasts. It becomes apparent
that the business case is often based on very favorable assumptions and estimates. Only
the control leads to the objectification of the imaginary profiles. The control goals are
determined by the monitoring and review of the results.
Control activities must not be limited to the duration of the project. Checks must also
be carried out after the project has been completed for a specific period. Under this
prerequisite, the company can recognize concretely how the planned benefit will be
achieved.
A plan/actual comparison can be carried out using a report. The variances can be rec-
orded, analyzed and justified. The planned/actual comparison compares the planned
values (target) with the actual values (actual). If variances exists, the causes of the var-
iance are investigated. Only by providing information about the cause of the variance
can you take corrective action [10].
Deviations are recorded by three variables:
• Planned size: The planned value estimated in the profitability analysis. It is the
planning basis for project approval.
• Target size: Calculated by adjusting the planned value based on current facts.
• Actual size: The actual value [11].
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Elementary decisions are made in order to achieve the project goals. The decisions are
made based on the deviation analysis. If there are deviations in the negative area, the
reasons must be clarified. Once the cause has been localized, countermeasures can be
taken. This can take the form of countermeasures. If the control recognizes that the
project goals are not reached, then the countermeasure can be undertaken for the reach-
ing of the project goals [12].
In summary, controlling can contribute to achieving the project goals and thus also the
benefits of the project. For the application of mathematical optimization methods for
sequencing, however, it must be assumed that the project goals and thus the calculated
contribution margins are achieved.
1.4. The state of the art in research for sequence problems
Multi-project planning also includes determining the optimal sequence in which the
projects are to be implemented. In today's literature there are two problems in the field
of operation research that deal with sequence problems. All two problems show a cer-
tain similarity to the multi-project sequence planning problem. These are the flow shop
problem and the job shop problem.
The Flow Shop problem deals with the problem of the sequence of machine utilization.
The machine sequence is defined from the beginning. The jobs to be processed are
divided into partial processing steps TBi with i = (1, 2, …). Each TB is processed by a
specified machine. In the problem definition there can be up to m machines and j jobs
[13].
Fig. 1. Simple Flow Shop Problem with m machines [14]
Generally speaking, the flow shop problem is more complicated than illustrated in Fig-
ure 1. The jobs can have less than m operations. Thus the jobs do not run through all
machines. At the start time t = 0, there are n independent jobs with m operations each.
The sequence of the jobs is known and has no preparation times for processing or is
included in the processing time of the job. All machines are available at any time and
no processes are aborted [15].
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Fig. 2. General Flow Shop Problem with m machines [16]
A job shop problem exists where all work steps for each machine are not necessarily
identical. Time-limited resources are allocated to process schedules. Sequences are de-
fined for the individual order instances. This means when and on which production
machine a work step takes place. [17].
Sequence A
M
1
M
2
M
3
Time t
Sequence B
M
1
M
2
M
3
Time t
Fig. 3. Example for Sequencing of three projects and three machines
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2 Further Research
The multi-project sequencing problem, on the other hand, differs in several respects
from the problems presented. A major difference is the question whether existing pro-
jects should be implemented. This condition results in a nonlinear constraint. Thus, the
multi-project sequence planning problem is a non-linear optimization problem (NLP
for short). The constraints are linearized by the use of auxiliary variables. Thus the NLP
becomes a linear problem (short LP). There are p projects in the problem definition.
Only n projects can be implemented in the given time T, (𝑛 ≤ 𝑝). Thus a prioritization
of the projects takes place. The difference of the multi-project sequence planning prob-
lem leads to the fact that no research in this direction can be found. The problem is
initially defined and solved as an LP problem. Algebraic modeling languages (software
like GAMS) are used for the solution. Furthermore, the solvers SIMPLEX and
GUROBI have to be compared. Further contents will be clarified during the research.
The research leads to the first solution for the existing problem.
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