14-12-2012, 04:02 PM
Location Dependent Query Processing
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ABSTRACT
The adv ances in wireless and mobile computing allow a
mobile user to perform a wide range of aplications once
limited to non-mobile hard wired computing environments.
As the geographical position of a mobile user is becoming
more trackable, users need to pull data which are related to
their location, perhaps seeking information about unfamil-
iar places or local lifestyle data. In these requests, a loca-
tion attribute has to be identied in order to provide more
eÆcient access to location dependent data, whose value is
determined by the location to which it is related. Local yel-
low pages, localev ents, and weather information are some
of the examples of these data.
INTRODUCTION
Location of an object or a person is its geographical posi-
tion on the earth with respect to a reference point. This
information can be characterized by using a number of dif-
feren t represen tations including latitude/longitude/altitude
or street addresses, etc. and by giving granularit y, accuracy
and rate of change (velocity). With the technological ad-
vances in cellular communications and sensing appliances,
location of people has become more real-time and trackable
[7]. Locationrepresen tation may include timestamp infor-
mation as it may be related to a moving object/person [5],
[16], [18] and may be represented in v arious ways. Location
can be estimated by using dierent methodologies, and will
become an information as common as date information.
LOCATION AND QUERIES
Queries asked in the mobile environment may have slightly
dierent structure from traditional database queries. In this
section, we examine the dierences and propose approaches
to process these. Obviously, there will be location related
and non-location related attributes in these queries. When
the user is moving, to answer an y location based request,
it may become necessary to identify location related at-
tributes. Sometimes the statement of the query will not
ha ve any location related attribute but the way it is stated
will have an implication that the query issuer's current po-
sition is in volved in the selection criteria. The implied lo-
cation related attribute has to be addedthtoe query and
corresponding LDD is used to answer it. An investigation
of implementation issues of location dependent query pro-
cessing can be found in [17]. We presen t a formalization for
the location identication in queries and give examples in
the follo wing subsections.
Location Dependent Queries
In Location Dependent Query Processing, we see a specic
type of predicate in which the location attribute is xed but
the constant to which it is compared changes depending on
the query issue location. As mentioned before, the predicate
is actually hidden in the query statement. For example, the
query \Find hotels within 5 miles." has the implied meaning
of \Find hotels within 5 miles of my current location." This
current location must be found and bound to the query. We
assume that some location service is used to provide this
location. This process of binding the current location to the
query is referred to as location binding.
SUMMARY AND CONCLUSION
In this paper, we have presented a query formalization which
would encompass all types of previously proposed query
models (both location dependent and non-location depen-
dent). Our view for Location Dependent Queries and Loca-
tion Aware Queries implicitly indicate a translation process
tionary or Mobile. LR-Operators set includes Spatial Oper-
ators and more complex ones including time and orientation
(straight ahead, within, closest, nearby, in, etc.), i.e. LR-
Operators Spatial Operators.