A survey on optimal route queries for road networks

IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
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Volume: 02 Issue: 12 | Dec-2013, Available @ http://www.ijret.org 447
A SURVEY ON OPTIMAL ROUTE QUERIES FOR ROAD NETWORKS
Gopika N.A1
, S. Deepa Kanmani2
1
PG student, 2
Assistant Professor, Computer Science and Engineering, Karunya University, Tamilnadu, India,
gopika.nasa@gmail.com, deepa_cse@karunya.edu
Abstract
In daily life the need to find optimal routes between two points is critical, for example finding the shortest distance to the nearest
hospital. Internet based maps are now widely used for this purpose. Route search and optimal route queries are two important classes
of queries based on road network concept. Route search queries find the route according to the given constraints. The optimal route
queries find the optimum route from a set of specifications by a user. In road map queries, users have to give the specification of
starting point and ending point of their travelling with or without constraints. Some spatial features about the categories and the
different locations should be specified along with this. If the travelling constraints are given then it should be unique. These
constraints may be either total order or partial order. In this specification order there should be information about both starting point
and destination point of the travelling. The optimal route queries optimize the possible routes and give the optimal route that satisfies
all the constraints. This paper describes the survey on optimal route query processing, two categories namely optimal route query
processing and spatial search with categorical information have been considered, a discussion on technique for optimal route query
with constraints and without constraint is also included. The total order needs a specification of list of points and in the same order
that they should be visited but that is not required for partial order constraints. Finally this paper concludes with pros and cons of
different techniques under optimal route queries.
Keywords: Query processing, optimal route queries, Spatial search, Categorical information, Constraints.
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1. INTRODUCTION
Query processing is the efficient retrieval of desired
information from the database system. The various phases of
query processing system are shown in the Fig 1. Four main
steps are there in the query processing where first three steps
are executed in compile time and last one in the runtime. The
route queries obtain the route from the spatial data with
categorical information stored in the database. The optimal
route queries find the optimal route from the given set of
information. The users have to give query starting point and
some travelling rules or constraints [4], [7] along with the
database which contains the categorical information about the
road map. Various techniques are used for the processing of
route queries. The some of the techniques used travelling rules
which are either total order or partial order and some other
without any specification. The given constraints may be either
total order or partial order.
Optimal route query processing finds all the possible routes
and then optimizes these possible routes. For that, route
queries operate on the spatial data with categorical
information [5], [8]. The goal is to find the optimal route from
the given queries.
In this paper, we discuss about various techniques in optimal
route queries. There are two main approaches: query
processing for optimal route [2], [3], [4], [7] and queries that
operate on spatial data [5], [6], [8].
Fig -1: Various Phases of query processing system
Relational
algebra
expression
Execution
plan
Generated
code
Query
output
System
catalog
Database
statistics
Main
database
Com
pile
time
Runti
me
Query
decomposi
tion
Query
optimizati
on
Code
generation
Runtime
query
execution
Query in high
level language

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The paper is organized as follows: section 2 presents the
problems in the optimal route queries. Section 3 and 4
classifies the optimal route query processing and the queries
related to spatial search with categorical information. The
advantages and disadvantages of each scheme are also
specified in this section.
2. PROBLEM STATEMENT
The optimal route query processing is mainly used in the road
network. The very first solution of the optimal route query is
based on the greedy strategy [1]. The first approaches
considered only the end points. The later approaches used
some category sequences as the input for the optimal route
queries that is some of the constraints are considered.
Different types of constraints are combined with the query.
Apart from the optimal route query some of the categorical
information is needed to consider for better surroundings and
facilities. For the effectiveness of some clustering techniques
are also discussed. Most of the techniques have limitations in
some particular area. The main problems are some of the
techniques may produce optimal route and others not. Among
this some may consider constraints and others without
consider the constraints and these are the main problems to
consider.
3. OPTIMAL ROUTE QUERY PROCESSING IN
ROAD NETWORK
3.1 On Trip Planning Queries (TPQ) in Spatial
Database
On Trip Planning Queries [3] are the efficient and exact
solutions for the general optimal route queries. A set of point
of interest (POI) of different categories, starting point and
destination point is given and TPQ [3] finds the best trip
starting from the specific source and will ends on the
destination through some POI. There are no ordered
constraints here in this method. The existence of multiple
choices per category is the main difficulty of this technique
and for solving this some of the approximation techniques are
used.
Mainly two greedy algorithms are available with the tight
approximation ratios with respect to the total number of
categories. The first algorithm is the nearest neighbor
algorithm. This algorithm find the best trip by visiting the
nearest neighbor of the last category to be added and that have
not been visited at that particular moment. The route thus
formed from source to destination point which is specified by
the user. The second one is the minimum distance algorithm
which introduces a novel greedy algorithm and while
comparing with the first one this is having the better
approximation bound [3]. This will find the set of vertices
with minimum cost. In this paper the nearest neighbor
algorithm is used to finds the better route starting and ending
at specific points. The advantages of the On Trip Planning
Queries include 1. Approximation ratio is high, 2. Minimum
cost for route finding. The disadvantage includes 1. No user
defined constraints in the TPQ.
3.2 The Optimal Sequenced Route (OSR) Query
The Optimal Sequenced Route Query [7] is a type of Nearest
Neighbor query and it finds the optimal route that starts from a
specific location and passed through a number of typed
location in some specific order. The shortest path problem is
the basics of this technique. First of all the OSR problem is
transformed into a simple shortest path problem in large planar
graph. For that the Dijkstra’s algorithm [7] is used. The OSR
query is given with starting point, a set of intermediate points
and the sequence of the locations. The weighted directed
graph is constructed from the given network. The starting
point is connected to all the other vertices and the weight
assigned to each edge of graph is the distance between two
end vertices. From this the optimal route of the OSR query is
the route or set of points with minimum length. The shortest
path finding is by travelling from starting point to all other
points and returning the minimum path length and this is done
by the Dijkstra’s algorithm. But this classic Dijkstra’s
algorithm is impractical due to the following reasons. The first
one is, in the real world dataset millions of possible edges
have to be handles so the time complexity is very high. Thus
the complexity of the algorithm is also very huge.
To improve the problem occurred due to the Dijkstra’s
algorithm the range query can be used. Even then the problem
cannot be overcome. Therefore Light Optimal Route Discover
(LORD)[7] algorithm developed for handling OSR queries.
This is an iterative and a light threshold based algorithm,
which uses different thresholds to filter out the points that
cannot be the optimal route. The memory requirement for
LORD is very much less than Dijkstra’s algorithm therefore it
is named as light. First this algorithm generates a set of partial
sequenced routes in the opposite order. That is from the
destination point to the starting point. Attach each point to the
recently added one and finally forms the optimal route.
The next one is R-LORD [7] algorithm which is an enhanced
version of LORD algorithm. It is based on R-tree and it
calculated the threshold value more efficiently. This is the first
correct solution for the optimal route queries with total order
travelling rules. R-LORD uses the greedy algorithm to find the
optimal route and the threshold value. From the end category,
finds the optimal points in the sequence and within the
threshold distance to the query point. Iteratively finds the
optimum route.
3.3 The Multi-Rule Partial Sequenced Route Query
The optimal route computation is purely based on greedy [1]
solutions in the earlier stages. This uses two approaches. The
first one is Nearest Neighbor Partial Sequenced Route

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(NNPSR)[2] which works similar to greedy approach. This
will start from the query start point and find the point which is
nearest to the start point and forms the edge. Then using the
newly added point finds the nearest point and forms the route.
The final route will be optimal through this greedy approach.
That is it finds the best at that moment. The second approach
will find all the nearest points from each and every category
and forms the route. This is also optimal route with in a
particular range.
Then another approach is the combination of NNPSR and R-
LORD [7]. The NNPSR is used to obtain the greedy route.
From that it obtains the category of each and every point. This
total order of categories is the input of R-LORD. And it will
output the suboptimal routes.
4. SPATIAL SEARCH WITH CATEGORICAL
INFORMATION
4.1 Top-K spatial Preference Queries
The spatial preference query [8] is used to rank the objects
from the feature qualities of the neighborhood objects.
Generally Top-K spatial preference queries are used to rank
the spatial objects effectively. Different types of algorithms
are used for this ranking. First one is a baseline algorithm
named simple probing algorithm and which applying the
spatial queries on feature dataset and calculate the scores for
every object. Thus the ranking is done. The incremental
computation techniques are used to optimize the simple
probing algorithm and which minimizes the number of
computations of component scores.
A variant of simple probing algorithm [8] is the group probing
algorithm and which computing the object scores in the
particular leaf node repeatedly and thus reduces the I/O cost.
Branch and Bound algorithm [8] is the enhanced version of
group probing algorithm, which removes the entries other than
the leaf nodes in the object tree that cannot produce better
performance. For this a new method is used by accessing
feature trees and deriving upper bound scores for the entities.
The last one is feature join algorithm [8] which performs over
the feature tree by multi-way join used to find the group of
feature points and then search for the objects using this
grouping.
4.2 Categorical Range Queries (CRQ) in Large
Databases
The categorical range queries [5] in the large database are
handled through the paper. Mainly it is related to the spatial
data like geostationary information systems. For this technique
a multi tree indent is used and which is associated with an
effective way of categorical data and spatial information. The
main concept is the augmentation [5] of categorical points
with some information to accelerate the queries.
The technical parts are a new method for spatial data structure
and R-Tree based on the query processing of CRQs in the
context of large databases. The new method is compared with
two baseline algorithms. The first one is the regular range
query [5] which handles the query for the particular range of
lower and upper boundary. The second one is the construction
of R-Tree [5] which contains the nodes that are the categorical
attributes.
4.3 Query Processing in Spatial Network Databases
The query processing in spatial database [6] is mainly based
on Euclidean spaces. But in this paper a new architecture is
proposed in which the road network is separated from the
datasets. To gather connectivity and location, a disk-based
representation is used. For handling the dynamic updates and
Euclidean queries the spatial entities are scored by some of the
corresponding spatial access methods. Based on the above
architecture two techniques are developed which are
Euclidean restriction and network expansion. The most
common spatial queries are the range search queries, nearest
neighbor queries, closest pair queries and distance join
queries. These are processed by using the above mentioned
frameworks. By using the location information and
connectivity, the efficient pruning of the search space is
possible. Through this the traditional processing methods can
be expanded by the new algorithms. The query processing in
the Spatial Network Databases (SNDB)[6] in efficient and this
paper introduces this advantage.
4.4 Optimal Route Query with Arbitrary Order
Constraints
The optimal route query considers the partial order constraints
for finding the optimal route. The user wants to specify
starting point, destination point and a set of arbitrary order
constraints [4]. This is different from the total sequenced rules.
The example for the partial order constraints is “visit the pub
before hotel”. Therefore any other categories can be included
in between these two categories. But total order is the
sequenced route conditions.
For considering the partial order constraints two different
types of techniques are developed namely Backward search
and Forward search [4]. Both the methods will take the same
inputs and will produce the same output. The backward search
algorithm finds the optimal route in the reverse manner that is
starting from the destination and ends at the query starting
point. This is similar to the R-LORD algorithm [7]. First select
the destination point and as per the partial sequenced route
find out all the possible edges to the second last point. Then
find the optimum edge from these and attached to the
destination. Then repeat the process until the query starting
point encountered.

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The second one is Forward search algorithm and which is
similar to the greedy algorithm [1]. First select the query
starting point and then find the nearest neighbor point which
satisfies the given constraint. The process repeats and finally
one optimal route is obtained. Then this forward search
algorithm will use the backward search algorithm for the
backtracking process. This will eliminate the demerits of the
greedy algorithm. That is it eliminates some points that will
not be a part of the optimal route. Both the algorithms find the
optimal routes and which satisfies all the given partial order
constraints. The memory usage is reduced by using some
pruning techniques. Thus the number of categories from the
dataset is reduced and the memory usage will be reduced.
This paper which uses both the optimal route query processing
in road network and the spatial search with categorical
information. Thus the methods used here is included in both
the classifications. This technique solved the problem of
optimal route query with partial order constraints [4]. Another
advantage is that several sub routes also can be obtained and
are optimal. Therefore in the real world application some of
the category points can be omitted to meet the particular cost
or the time.
5. CONCLUSIONS
The optimal route queries find the optimal route and this has
greater applications in the road network. The spatial search
with categorical information is used to consider the categorical
points to be visited with better facilities. The initial solution of
the optimal route query is based on the greedy solution. Some
of the techniques considered total order constraints. The recent
solutions of the optimal route query handle the arbitrary order
constraints. All the methods will result in the optimal solutions
with the given the starting and destination points. But many of
the techniques do not consider constraints. Some may consider
the total order constraints and some others use the partial order
constraints. In future, some of the timing constraints can be
included to the optimal route queries.
ACKNOWLEDGEMENTS
I feel it pleasure to be indebted to my guide Mrs. S. Deepa
Kanmani, M.E, Assistant professor, Department of Computer
Science and Engineering for her invaluable support, advice
and encouragement and the reference for her feedback.
REFERENCES
[1]. Boinski P, Wojciechowski M, Zakrzewicz M(2007), “A
Greedy Approach to Concurrent Processing of Frequent
Itemset Queries”, Proc. Of the International IIS: IIPWM’06
Conference
[2]. Chen H, Ku W.S, Sun M.T, Zimmermann R(2008), “The
Multi-Rule Partial Sequenced Route Query”, Proc. 16th ACM
SIGSPATIAL Int’l Conf. Advances in Geographic
Information Systems (GIS)
[3]. Li F, Cheng D, Hadjieleftheriou M, Kollios G, Teng
S.H(2005), “On Trip Planning Queries in Spatial Databases”,
Proc. Ninth Int’l Conf. Advances in Spatial and Temporal
Databases (SSTD)
[4]. Li J, Yang Y.D, Mamoulis N(2013), “Optimal Route
Queries with Arbitrary Order Constraints”, IEEE Trans.
Computers, vol. 25, no. 5, pp. 1097- 1110
[5]. Nanopoulos A, Bozanis P(2003), “Categorical Range
Queries in Large Databases”, Springer-Verlag Berlin
Heidelberg, pp. 122-139
[6]. Papadias D,Zhang J, Mamoulis N, Tao Y(2003), “Query
Processing in Spatial Network Databases”, VLDB conference.
[7]. Sharifzadeh M, Kolahdouzan M.R, Shahabi C(2008),
“The Optimal Sequenced Route Query”, VLDB J - Int’l J.
Very Large Data Bases, vol. 17, no. 4, pp. 765-787
[8]. Yiu M.L, Mamoulis N, Vaitis M(2007), “Top-k Spatial
Preference Queries”, 7160/05E from Hong Kong RGC
BIOGRAPHIES
Gopika N.A pursuing her M.Tech in Computer
Science and Engineering from Karunya
University, Tamilnadu, India. She received her
Bachelor’s degree from Lourdes Matha
Engineering College under Kerala University
in Computer Science and Engineering.
Mrs. S. Deepa Kanmani received her Master of
Engineering degree from the Anna University,
India. Currently she is pursuing her Ph.D
degree in Distributed Data Mining & Database,
Karunya University, and Coimbatore. She is
working as an Assistant Professor in Computer Science and
Engineering Department, Karunya University, Coimbatore.

A survey on optimal route queries for road networks

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