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Evaluation, RP = Retirement Plan, F = Full time instructor, P = Part time instruc-
tor, I = Instructor, D = Department, H = Head, LT = Lecture, and LB = Lab. In this
example, we have redundant repeating data values 65 in the attribute Age of ele-
ment Retirement Plan.
When we design an XML schema in tree structure, we must start at root element.
Under the root element, we can implement data semantic of user requirements in a
vertical fragment connected to the root element. Each one of data requirements can
be implemented by a fragment under the root element. These fragments use refer-
ence pointers to implement the required data semantics according to the template in
Fig. 9.17 such that each data semantic is implemented by a fragment under the root
element in bracket.
The following are the description of how each data semantic can be specified
in FD (functional dependency) and ID. These data dependencies are mapped into
DTD Graph, and DTD. This section describes how to reduce data redundancy, and
improve performance by reducing reference pointers among the elements in XML
schema. The method is to introduce DTD Graph as XML conceptual schema, which
are mapped into DTD as XML logical schema with minimum reference pointers and
no data redundancy, and above all, with many data semantics such as cardinality,
participation, isa, generalization, categorization, aggregation, n-ary relationships,
and u-ary relationship as shown in Fig. 9.17 .
Step 1: The initial Semantic template and its data for each semantic is shown in
Fig. 9.18 as follows:
Teaching
*
*
*
*
*
*
idref
*
*
*
*
id0
sname
(j)
Lecturer
(a)
Employee
(c,h)
Instructor
(b)
Department
(i,j)
Tutor
(j)
Professor
(d,f)
Part Time
(g,i)
Course
(h,i)
Student
id8
(d,e)
Full Time
id5
id3
id1
id9
idref
910
id10
id
idref
?
?
|
id4
+
*
+
|
(k)
Artifact2
(b)
Head
(e)
Retirement
Plan
(k)
Artifact1
(f)
Hourly
Rate
(h,i)
Artifact5
(g)
Lab
(g)
Lecture
(d)
Artifact4
(d)
Artifact3
id2
Age
*
idref
1
idref
2
HW
lbname
ltname
idref
4
idref
3
(h)
Artifact
evaluation
idref
5
Fig. 9.18 XML document with data redundancy and many fragments
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