A BI-CRITERIA SCHEDULING FRAMEWORK FOR THE
SUPPLY CHAIN MANAGEMENT OF MOBILE PROVIDERS
Göktürk Gezer, İlker Yaz, Hasan Mert Taymaz, Tansel Özyer
Department of Computer Science, TOBB ETÜ, Ankara, Turkey
Reda Alhajj
Department of Computer Science, University of Calgary,; and Dept. of Computer Science, Global University, Lebanon
Keywords: Scheduling, delivery, agent, PDA.
Abstract: In delivery sector answering the requests of customers quickly and efficiently became very important for
recent years. Thus people who are working in delivery sector began challenging to build well settled
synchronization for more complex delivering system. In this synchronization they try to keep customers
information, providers (who answering requests) information, divide requests for providers and inform them
about their recent jobs, provide fast and efficient delivering system. All of these lead to acquire customer
pleasure with firm pleasure. We believe that using mobile device such as PDA with a host PC for building
well settled synchronization with providers and host is simple but useful way. The aim of host is arranging
received requests and sending them with their information to convenient providers by considering all
providers position and their job intensity. So request would be answered as quickly as possible. Also
providers can access information about their jobs and the shortest path for reaching these jobs by using their
PDA. Our system makes all things simple and easy for people. Providers don’t have to care about how to
reach their jobs and workers arrange requests don’t have to consider about convenient providers.
1 INTRODUCTION
Mobile devices are employed in several real life
applications. Supply chain management is one of
them. It includes the movement of production from
supplier to customer; submitting the delivery with
delivery status; and financial flow such as terms and
payments scheduled. Vehicle routing problem paid
an attention by researchers (Bodin et al., 1983)
(Desrosiers et al., 1995). Vehicle routing is
important because a system needs an optimized
scheduling of deliveries. It can be a service,
delivery, transportation, freight. Several
optimization methods have been optimized. There
are some heuristic methods (Lee et al., 2001)
(Savelsbergh, 1985) (Desrochers et al., 1992),
Genetic algorithm based solutions (Jr. and
Wainwright, 1991). It was also investigated adjunct
to data structures such as trees (Muslea, 1996).
The rapid development of supply chain
management between logistics and supply
information chain management between providers
and host, the most important problems are arranging
system for a lot of providers and customers, supply
data transfer between providers-host and finding the
most convenient providers for customers. In solution
of these problems we use mobile devices (for
providers) and PC(for host) for providing connection
and through this connection after taking requests,
convenient providers are selected and informed
about these requests. Process of deciding the
convenient provider two priorities of source
management that can decide by users of system are
considered. One of these priorities is choosing
closest provider (by looking his last jobs location
because after he answered his all jobs he will be at
this location) irrespective of how many jobs he has
and when he can answered the job. Second of them
is choosing the provider that can answer request
more quickly than others irrespective of distance
between provider and job. Also we use providers’
last job location instead of providers’ real time
location. So we don’t have to connect all providers
to learn their location while deciding convenient
provider. When host decided convenient provider, it
inform him about job and ask him if he accepts job
364
Gezer G., Yaz Ä
ˇ
r., Mert Taymaz H., Özyer T. and Alhajj R. (2008).
A BI-CRITERIA SCHEDULING FRAMEWORK FOR THE SUPPLY CHAIN MANAGEMENT OF MOBILE PROVIDERS.
In Proceedings of the Tenth International Conference on Enterprise Information Systems - AIDSS, pages 364-369
DOI: 10.5220/0001718603640369
Copyright
c
 SciTePress

or not. Unless taking negative answer from provider,
host adds information of the job in the provider’s
jobs information. If provider refuse the job,
information about job send second convenient
provider and ask him to accept job. So we avoid
unnecessary data transfer (for example informs all
providers about job) by choosing the most
convenient provider for a job. Also we give a chance
to users to choose their priorities (the closest or the
fastest) while deciding convenient provider. These
priorities make the choice convenient provider part
flexible.
Information that is sent to providers includes the
shortest path between him and job. Provider can see
this path by the agency of map in his PDA. Also he
can know estimated delivery time for jobs. In
addition to this, we don’t supply connection provider
to provider for keeping data transfer fast between
providers and host.
2 SYSTEM ARCHITECTURE
Our system does the part for preparing any map for
simulation. Paths can be bidirectional besides one
way or blocked at a degree. Also the implementation
runs on two different types of party. Host and PDAs.
2.1 Preliminary Work
2.1.1 Road Segmentation
Distances between road pieces must be stored to
compute distances between points for scheduling
deliveries on the map. In order to make it possible,
maps must be digitalized into memory. We have
created our own data structure called “Multi Linked
List” that is used to keep map locations. Figure 1
shows how the map is divided into segments
conceptually.
In our application we prepared supporting
software for preparing a map. It helps us code road
pieces’ information. By using this program we have
created the necessary codes to make any map, and
then our application pre-processes and stores map
data in multi-linked list information. We have
created the necessary codes to implement the map.
In our system, the central host and PDAs use a
common map. It is a real map that takes all the
connections and directions into account with road
status that is caused by several reasons such as
weather, pavement, traffic and etc. Before the
application runs, the map should be processed to
capture the road information like a real map. Our
implementation partitions the roads into segments.
Figure 1: Constructing map.
Multi linked list structure is employed to
represent connections.
The suggested multi linked list data structure is a
union of multi linked nodes. Each multi linked node
contains following information about road piece:
Road’s piece number, road’s length, road’s activity,
road’s traffic intensity, list of connected road pieces
to road.
2.1.2 Containers
We have created three containers to keep the data in
our project. All three are explained below.
Type I Container: This container is created for
encapsulating the information about job. It has types
for keeping typical information and location
information about the job.
Three classes are defined. They store the job
information (Descriptive Information), Road
Information, and Schedule Definition.
Type II Container: It contains the tree structure for
our path finding algorithm.
Type III Container: It stores our multi linked list
implementation for digitalizing the map. It has two
classes for map and road segments each.
A BI-CRITERIA SCHEDULING FRAMEWORK FOR THE SUPPLY CHAIN MANAGEMENT OF MOBILE
PROVIDERS
365

2.2 The Implementation
There are two main parts interacting for scheduling
jobs. They are namely Host module and client
module. Master-slave multi-agent approach is
adopted. Host component makes computations and
make decision. Although clients have the freedom of
act in an environment, and clients’ responsibility is
to do orders received by host. Clients may accept or
deny requests from the host.
2.1.2 Host Agent
Host agent is the coordinator agent for the
scheduling. It undertakes the responsibilities as
following:
• Editing the properties about roads. That
properties include roads traffic intensity
and whether it is open or not,
• Monitoring each connected provider’s
location in the map,
• Receiving the information about the job.
• Calculating this job’s needs according to
company’s source management priorities,
• Finding the ways that include shortest path
from each provider to customer, and then
sending them with the information about
job to the selected provider,
• Assigning the job to selected provider,
• Monitoring information about jobs by
categorizing them into pending, completed
and unassigned state,
When job has taken by provider, this job is
added to pending jobs.
When provider confirm that job has finished in his
program. Job is deleted from pending jobs list and
added to Completed Jobs list. You can also get
detailed view of the job by clicking this in the list.
2.1.3 Provider Agent
Provider agent is the client responsible for doing the
job received from host. There is one host and
multiple providers. Providers can get connected to
the system. There is no limitation of number of
providers. Client agent’s functions and
responsibilities are followings:
• Accepting the job received from host or
denying it.
• Keeping list of pending jobs.
• Showing the information about handling
job.
• Informing the host about completed jobs.
When host send a job to client a MessageBox
appears on the client screen. In this screen provider
is informed about when he can start the job and
when it is responsible to finish it. If provider selects
“YES”, job is assigned to provider and it is added to
client program’s pending jobs list. If provider selects
“NO”, job information iterates over other providers.
Figure 2: Proposing Road to Provider
Road manipulation is also useful property of
client program (Figure 2). By clicking next, previous
and “En Kısa” button, provider can iterate over
roads from himself to customer (Figure 3). When
provider clicks one of these three buttons, road on
the map and information related to road changes
according to clicked button.
Figure 3: Listing of Optimal Paths.
When provider finishes the job he must click on
the “İş Bitti” button. After clicking, information
about job is removed from client program then on
the host side and added to completed jobs list.
ICEIS 2008 - International Conference on Enterprise Information Systems
366

3 COMPONENTS
3.1 Host Agent Components
There are three components that are linked to host.
Host is “singleton activated host” for these
components. Host itself is also client for them.
ServiceProviderInfo Component: This component
is responsible for keeping and serving ID and IP
information about connected providers. All clients
are connected to this component. They record
trajectory information of clients.
JobInfoManagement Component: This component
is responsible for keeping and serving job
information. After host sends job information to the
DecisionMaker component, decision maker tries to
assign this job to client. When a client accepts the
job, decision maker add this job information to the
JobInfoManagement component.
DecisionMaker Component: It is responsible for
making distance - time consumption calculations
and assigning the job to provider by co-operating
with all providers. DecisionMaker is client for
JobInfoManagement, ServisProvider Info
components of host and Responder component of
client.
Algorithm 1: Main Distribution Algorithm.
//This algorithm is responsible for creating
IsBilgileri object for each provider and sending
them to providers.
Input : TanimlayiciBilgiler object
For each connected provider
Begin
Retrieve providers last location
Find the ways from provider to customer(*).
Create YolBilgileri object from these ways
and sort the list in ascending order
Create IsBilgileri object and add this to
the “Isler” list
End;
Isler.Sort( Comparer object)
For each IsBilgileri in “Isler” list
Begin
Establish connection to provider’s
Responder component
If (provider accepted the job)
Add this job to pendings list
Break
End
In this algorithm providers last location means that,
if provider has no pending jobs it last location is its
real-time location, if it has some pending jobs, its
last location is its last customer’s location. Comparer
object that is used to sort “Isler” list is created by
host according to priorities combo boxes.
Find the Ways from Provider to Customer (*): It
finds and scores all possible ways from provider to
customer and sorts them in descending order.
3.2 Provider Agent Components
There are two components in client side. Client is
“Singleton Activated Host” for these components.
TaskHandler: It is the main component of client
program. It is responsible for keeping records of
received job’s information. This information
includes roads, customer information and time
information.
Responder: This component is the interface
between host components and TaskHandler
component of client. When decision maker sends a
job to client it connects to client’s Responder
component, then Responder asks for approval to
provider by viewing confirmation box.
4 DYNAMIC CONFIGURATION
4.1 Closing Traffic Stream on Road
In host program, operator can close particular roads
for traffic stream. When road is closed, that passage
won’t be used in finding algorithm. This is how we
do and how it affected the algorithm below in Figure
4. You can see that closed road hasn’t used for
shortest path from provider to customer though they
are in the same location. This shows that our
experiment result for road closing is successful.
Figure 4: Path with Minimum Distance after Block.
4.2 Changing Road Intensity
Different traffic intensity of the same path changes
estimated time. We have done that by changing the
A BI-CRITERIA SCHEDULING FRAMEWORK FOR THE SUPPLY CHAIN MANAGEMENT OF MOBILE
PROVIDERS
367

route’s road pieces’ traffic intensity from host
program. When traffic intensity for all road pieces
are 50 percent, it takes 8 time units and when
intensity for selected road pieces are 80 percent it
takes 11 time units. This results show that our
experiment for changing traffic intensity is
successful.
Figure 5: Route Intensity Value at 80%.
5 THE EXPERIMENTS
We have done a lot of experiments to prove our
system’s benefits and correctness. This application
presents a framework for carrying out simulations.
At the same time, this application can be controlled
manually and work on real PDA devices. We have
taken experiments on a map.
We assumed there are 8 and 10 providers to
complete 25 jobs for the experiments. Figure 5 and
Figure 7 give the meters taken per job; Figure 6 and
Figure 8 give the results for the delay per job for 6,
8, and 10 providers respectively.
In each figure results belong to different cases.
Random provider method is totally random. Jobs are
scheduled for random providers.
Table 1 gives the results for all cases. Our
method using total way taken and the delay for
delivery were the main criteria for scheduling the
agents for the supply chain management. In all
methods increasing the number of providers
increases the performance of delivery. Our algorithm
is by far the most efficient system for each case.
Both the delay and total meters taken (fuel
consumption) are minimized. Decreasing the
importance of meters taken causes total distance to
increase and delay accordingly.
Figure 6: Service Delay for 8 providers.
Figure 7: Road Taken for 10 providers.
Figure 8: Service Delay for 10 providers.
Dedicated provider method shares the area
equally as one provider per zone.
Others give weighted importance for two
different criteria, total meters taken throughout the
deliveries, and the delay for all submissions.
In this study, at the beginning we have to burn-
in the system for all cases in order to obtain the
maximum and minimum values to normalize the
values. Delay duration is given a pre-specified unit
of time, 15.
ICEIS 2008 - International Conference on Enterprise Information Systems
368

Table 1: Total Mt. and Avg. Delay For 6,8,10 Providers.
Road Taken
(meters)
Average
Delay
8 10 8 10
0-1.0 105870 105870 4,52 3,6
.2-.8 90180 89160 4,6 3,32
.4-.6 80600 82340 4,8 3,72
.5-.5 85740 86800 4,84 4,48
.6-.4 80600 79870 4,84 4,4
.8-.2
85740 91129 6,44 4,48
1.0-0.
84880 94100 5,64 5,68
Dedicated
151431 137080 12,4 8,64
Random
195390 186430 16,72 14,88
6 CONCLUSIONS
Scheduling is an important issue and in this study,
we have implemented a system that can be run for
both real life system and simulation purposes. Given
a map of a location, this system can be installed on
PDA devices and can be used for communication
between the PDA devices and the host. PDA users
can communicate; accept/deny the upcoming
requests for delivery, report deliveries, update traffic
status, any block, and revoke any job. In addition to
these, a framework for simulating the scheduling
process can be configured. The number of providers,
speed can be adjusted for each independently.
Dynamic changes regarding the map can be set with
parameters. Different jobs can be created. Finally
results can be obtained with bi-criteria method. Also,
random providers and dedicated provider methods
have been implemented in this study. All these
methods have been experimented and results convey
us to use bi-criteria method for scheduling.
7 FUTURE WORK
In our project we use a small map and simulation of
GPS (by clicking on map in provider system) rather
than large area map and connection with GPS. In
process of improving our project, large and real map
can be appended the system and association between
client system and GPS can be provided. Also instead
of using our helper program, constitution of road
piece can be done automatically by a program which
can recognize road piece (may use unique colour in
roads). In addition to this, our master-slave model in
communication of provider and host , providers can
communicate with each other and exchange work in
unexpected situation such as closed road that don’t
be declared before. Also the map can divide pieces
and providers can be assigned his special piece
where they taking request from customer in. Number
of providers for each piece can be determined
considering number of request for that piece. Also
communication of provider can be restricted. For
example only allow communication for providers
that stand at the same zone. So we can avoid
complex and unnecessary communication. It comes
with advantage of keeping data transfer over the
internet connection of PDAs fast.
ACKNOWLEDGEMENTS
The authors would like to thank to Eminay
Yurtseven on behalf of Microsoft Academic
Programs Management, Developer & Platform
Group, Microsoft Turkiye for the support of this
work.
REFERENCES
K. Tan, L. Lee, Q. Zhu and K. Ou, "Heuristic methods for
vehicle routing problem with time windows",
Artificial Intelligence in Engineering, 15, 281-295,
2001.
I. Muslea, “The k-Vehicle Routing Problem in Trees”,
M.S. thesis, Department of Statistics and Computer
Science, West Virginia University, 1996.
Savelsbergh, M. W. P., “Local search for routing problems
with time windows”, Ann. of Operations Research,
4:285-305, 1985.
Jr., J. L. B. and Wainwright, R. L, “Multiple vehicle
routing with time and capacity constraints using
genetic algorithms”, In Proceedings of the Fourth
International Conference on Genetic Algorithm., pages
452-459, 1991.
Lawrence Bodin, Bruce Golden, Arjang Assad, and
Michael Ball, Routing and scheduling of vehicles and
crews - the state of art, Computers & Operations
Research, vol. 10, no. 2, pp. 62 - 212, 1983.
Martin Desrochers, Jacques Desrosiers and Marius
Solomon, “A new optimization algorithm for the
vehicle routing problem with time windows”, Oper.
Res., volume 40, 2, 1992.
J. Desrosiers, Y. Dumas, M.M. Solomon, and F. Soumis.
“Time constrained routing and scheduling”, Network
Routing. Handbooks in Operations Research and
Management Science, Vol. 8, pp. 35-139, North-
Holland, 1995.
A BI-CRITERIA SCHEDULING FRAMEWORK FOR THE SUPPLY CHAIN MANAGEMENT OF MOBILE
PROVIDERS
369