Database Reference
In-Depth Information
In the following, we show a number of simple global fuzzy queries formulated using FTS-SQL over
the FTS relations given in Table 5, and explain their semantics. In every example we have assumed
α=0.8 and β=0.6 to indicate the precision of the fuzzy query.
With the source option [
sameDB
] assigned to SELECT clause,
Q
1 requires the projection of
Dept
to
include the source attribute (see Figure 2). Hence the fuzzy tuples with the identical projected attribute
values not source values remain to be separate in the fuzzy query result, e.g. information about
Eco
department. The two fuzzy values.6/mod and.63/mod are α-resemblant but the tuples related with
Eco
department are not merged rather remain to be separate in the fuzzy query result. If the source option
[
anyDB
] is not important during the projection, the source option can be assigned to the SELECT clause
as shown in the next fuzzy query example.
As shown in result of the fuzzy query
Q
2, fuzzy tuples that are α-resemblant are merged using fuzzy
union
and the source value of the merged tuple is indicated by '*' if the parent tuples come from differ-
ent source.
If it is required to view the result source context with the result tuples, the WITH clause is used as
shown in the next example
Q
3.
It can be observed that the addition of WITH clause causes the source relation given in Table 3 to be
joined with the FTS relation(s) in the WHERE clause using the source attribute. When the tuple has '*'
as the source value, its source context will carry 'Null' values for the context attribute.
DISTRIBUTED FUZZY QUERY PROCESSING ARCHITECTURE
Fuzzy Query Mediator and Fuzzy Query Agents
The proposed distributed fuzzy query processor has a fuzzy query mediator and for each local database
there is one fuzzy query agent. The responsibilities of a fuzzy query mediator are:
1. to take the global queries as input given by multi-database applications, and decompose it into
multiple sub-queries to be evaluated by the fuzzy query agents of the respective local databases.
For this decomposition process it has to refer to Global Fuzzy Schema to Export Fuzzy Schema
Mapping information. This unique information is supposed to be stored in the FMDBS.
2. to forward the decomposed queries to respective local fuzzy query agents.
Figure 3.
