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2010/03/30 1
Lecture 11 on Data Conversion
This lecture aims to describe the methodologies of converting relational database into object-oriented database, and converting relational database into XML document. Basically, the procedures are different due to their various data structures. Each data semantic conversion rule will be discussed in detail.
2010/03/30 2
Data Conversion: CUSTOMIZED PROGRAM APPROACH
• A common approach to data conversion is to develop customized programs to transfer data from one environment to another.
• However, the customized program approach is very extremely expensive because it requires a different program to be written for each M source files and N target.
• Furthermore, these programs are used only once.
• As a result, totally depending on customized program for data conversion is unmanageable, too costly and time consuming.
2010/03/30 3
N x M customerized conversion programs
:
:
:
:
:
:
:
:
:
:
:
:
:
:
1 1
n m
Source files Target files
Program(s)
2010/03/30 4
Data Conversion: INTERPRETIVE TRANSFORMER APPROACH
Definitions ofsource, target,and mapping
Interpretivetransformer
source target
Suppose that the database of a source nonrelational schema Ss is mapped to a target relational schema St. There are three distinct processes in this approach. One process accesses the source data(reading). Another process performs logical transformations on the data to place it into an internal form. A third process creates the target data (writing).
Descriptionof Source
RestructuringDescription
of Target
RestructureSource
ConverterTarget
converterSourceForm
normalForm
normalform
Targetform
Summary view
Detail architecture
2010/03/30 5
SDDL statements:Data Structure PERSON <NAME, AGE>Instance CARS <LIC#1, MAKE>N-tuples ACCIDENTS <LIC#2, NAME>Relationship PERSON-CAR <NAME, LIC#1>N-tuples CAR-ACCIDENT <LIC#1, LIC#2>
The TDL statements areFORM NAME FROM NAMEFORM LIC#1 FROM LIC#1:FORM PERSON IF PERSONFORM CARS IF CAR AND ACCIDENT
PERSON
NAME AGE CARS
LIC# 1 MAKE ACCIDENT
LIC# 2 NAME
Level 0
1
2
3
PERSON
NAME AGE CARS
LIC# 1 MAKE LIC# 2 NAME
Level 0
1
2
Example of Interpreter Statements
Source database Target database
2010/03/30 6
Data Conversion: TRANSLATOR GENERATOR APPROACH
The translator reads the source definition, the target definition, and the mapping definition, and then generates a specialized program that will reformat and map the stored data from source to target as illustrated below:
Translator generator
Definitions ofsource, target,and mapping
Specializedprogram
source target
Translatorgenerator
2010/03/30 7
DEFINE and CONVERT compile phase
Reader (S1)Reader (S2)
::
DEFINECompiler
DEF S1DEF S2
::
DEFINESource
Reader (DEFINE)compiler phase
PL/1Program
Convertcatalog
CONVERTprogram
Statement 1Statement 2
::
Restructurer(CONVERT)
compiler phase
DEFINECompiler
COP 1COP 2
::
PL/1Procedure
CONVERTCatalogue
ExecutionSchedule
2010/03/30 8
DEFINE and CONVERT statementsIts DEFINE statements:
GROUP DEPT:OCCURS FROM 1 TIMES;FOLLOWED BY EOF;PRECEDED BY HEX ‘01’;:END EMP;GROUP PROJ:
OCCURS FROM 0 TIMES;PRECEDED BY HEX ‘03’;
:END PROJ;
END DEPT;
CONVERT statement: T1 = SELECT (FROM DEPT WHERE BUDGET GT ‘100’);
will produce the following program:/* PROCESS LOOP FOR T1 */DO WHILE (not end of file);
CALL GET (DEPT);IF BUDGET > ‘100’
THEN CALL BUFFER_SWAP (T1, DEPT);END
2010/03/30 9
Logical level data conversion
We can download data from source database to a sequential file, and then upload the sequential file to a target database according to result of the pre-process schema translation.
The unload is done according to the source schema, and the reload is done according to the target schema.
In this case, there is no need for physical data type translation.
2010/03/30 10
Logical level data conversion from relational to object-orientedLogical level data conversion from relational to object-oriented
UnloadprocessRelational
database
Transfer
(optional)
Object-oriented
database
Uploadprocesssequential
files
Targetsequential
files
relationaldatabasetemplate
object-orientedschema
System flow diagram for data conversion from relational to object-oriented
2010/03/30 11
Methodology of data conversion from relational to object-oriented
Step 1 Translate relational schema into object-oriented schema.
Schema translation is done before data conversion. An relational schema can be translated into oodb schema by mapping relation into class, attributes an into attributes, foreign key into association attribute, and other constraints into method.
2010/03/30 12
Step 2 Unload relations’ tuples into sequential files
Step 2.1 Tuple insert statement
foreign key null value
The first substep is to unload each relation tuple into a file using insert statements (note: these statements will later be uploaded back to a target object-oriented database such that each class will be initially loaded from the tuples of a corresponding relation).
2010/03/30 13
Step 2.2 Foreign key Association Attribute update statement
Step 2.2 Foreign key Association Attribute update statement
For each foreign key, its referred parent relation tuple is unloaded into another file with update statements.
The referred child relation tuple is unloaded into the same file and use stored OID to replace foreign key.
The update statement is to place the correct value in the association attribute when they are uploaded to a target object-oriented database.
2010/03/30 14
Step 2.3 Superclass attribute subclass attribute Update statement
In the third substep, for each subclass relation, its referred superclass relation tuple is loaded into a third file with update statements.
It makes use of the stored OID when uploading the insert statement in the first substep.
2010/03/30 15
Step 3 Reload file to object oriented database
After unloading insert and update statements into sequential files, which can then be uploaded into object-oriented database according to the translated object-oriented schema.
In the process, OID will be generated for each tuple, and the generated OID(stored OID) is used to associate objects within each other.
2010/03/30 16
The pseudo code for this process can be described as follows:
Begin
Get all relation R1, R2….Rn within relational schema;
For i = 1 to n do /* first substep: load each class with corresponding relation tuple data */
begin
while Rj tuple found do
output non-foreign key attribute value to a sequential file Fi with insert statement;
end;
For j = 1 to n do /* second substep: update each loaded class with its association attribute value */
begin
while Rj tuple with a non-null foreign key value found do
begin
Get the referred parent relation tuple from Rp where Rp is a parent relation to Rj;
Output the referred parent relation tuple to a sequential file Fj with update statement;
Get the referred child relation tuple from Rj;
Output the referred child relation tuple to the same file Fj with update statement;
end;
For k = 1 to n do /* third substep; update each subclass to inherit its superclass attribute value */
begin
while a subclass relation Rk tuple found do
begin
Get the referred superclass relation tuple from Rs where Rs is a superclass relation to Rk;
Output the referred superclass relation tuple to a sequential file Fk with update statement;
end;
end.
2010/03/30 17
Case study of data conversion from relational to object-orientedCase study of data conversion from relational to object-oriented
Student
isa
GraduateStudent
enrol
Prereq
Student#student_namesex
Student#degree_to_be
Coursecourse_titlelocation
Inst_nameInst_addr
Section#lecture_hour
CoursePrerequisiteprereq_title
Prerequisite
n
m
n
Instructor section Coursem n
1
yeargrade
An EER model for the modified university enrollment systemAn EER model for the modified university enrollment system
2010/03/30 18
Record COURSE
COURSE
#
COURSE_LOCATION COURSE-TITLE LOCATION
IS101
IS201
IS301
LECTURE THEATRE 1
LECTURE THEATRE 2
ROOM P7818
INTRO TO COMPUTER SCIENCE
SYSTEM ANALYSIS
DECISION SUPPORT SYSTEM
LECTURE THEATRE 1
LECTURE THEATRE 2
ROOM P7818
Record PREREQUSITE
PREREQUISITE# PREREQUISITE_TITLE *COURSE#
IS201 SYSTEM ANALYSIS IS301
Record GRADUATE_STUDENT
*STUDENT# DEGREE_TO_BE
012880
120008
M.PHIL
PH.D
Record INSTRUCTOR
INSTRUCTOR_NAME INSTRUCTOR_ADDRESS
A.B. ADAMS
J.S. FINK
A.M. JONES
WHITE PLAINS
BROOKLYN
LONG ISLAND
Record SECTION
COURSE# INSTRUCTOR_NAME SECTION# HOURS
IS101
IS101
A.B. ADAMS
J.S. FINK
SECTION 1
SECTION 2
30
30
Record STUDENT
STUDENT# STUDENT_NAME SEX
012880
120008
117402
PAUL CHITSON
IRENE KWAN
JOHN LEE
M
F
M
Record ENROL
INSTRUCTOR_N
AME
SECTION# COURS
E#
STUDE
NT#
GRAD
E
YEAR
A.B. ADAMS
J.S. FINK
Section 1
Section 2
CS101
CS101
025056
312788
A
P
1995
1996
Source Relational Database Data
2010/03/30 19
Translated object-oriented schema in uni-direction association attribute Translated object-oriented schema in uni-direction association attribute
Class Student Class Graduate student attr student#: integer inherit Student attr student_name: string attr degree_to_be: string attr sex: string association attr register_by: set(enrol)End end
Class Section Class Instructor attr section#: integer attr inst_name: string attr lecture_hour: integer attr inst_addr: string association attr divided_by: course association attr teach: set(section) association attr taught_by: instructor end association attr provided_by: set(enrol)end
Class Course Class Prerequisite attr course: string attr course: string attr course_title: string attr prerequisite: string attr location: string attr prereq_title: string association attr prer_by: set(prerequisite) association attr prer: course assoication attr divide: set(section) endend
Class Enrol attr year integer attr grade: string association attr register ref graduate_student association attr provide ref sectionend
2010/03/30 20
Content of Fi for generated objectsinsert into student (student#, student_name, sex) values (‘012888’, ‘Paul Chitson’, ‘M’)
insert into student (student#, student_name, sex) values (‘120008’, ‘Irene Kwan’, ‘F’)
insert into student (student#, student_name, sex) values (‘117402’, ‘John Lee’, ‘M’)
insert into graduate_student (student#, degree_to_be, register) values (‘012888’, ‘M.Sc.’, null)
insert into graduate_student (student#, degree_to_be, register) values (‘120008’, ‘Ph.D.’, null)
insert into section (section#, lecture_hour, taught_by, divide, provide) values (1, 30, null, null, null)
insert into section (section#, lecture_hour, taught_by, divide, provide) values (2, 30, null, null, null)
insert into enrol (year, grade, register_by, provide_by) values (1995, ‘A’, null, null)
insert into enrol (year, grade, register_by, provide_by) values (1996, ‘B’, null, null)
insert into instructor (inst_name, inst_addr, teach) values (‘A.B.Adams’, ‘White Plains’, null)
insert into instructor (inst_name, inst_addr, teach) values (‘J.S.Fink’, ‘Brooklyn’, null)
insert into instructor (inst_name, inst_addr, teach) values (‘A.M.Jones’, ‘Long Island’, null)
insert into course (course, course_title, location, pre-by), values (‘IS101’, ‘Introduction to Computer Science’, ‘Lecture Theatre 1’, null)
insert into course (course, course_title, location, pre-by), values (‘IS201’, ‘System Analysis’, ‘Lecture Theatre 2’, null)
insert into course(course, course_title, location, pre-by), values (‘IS301’, ‘Decision Support System’, ‘Room P7818’, null)
insert into prerequisite (prerequisite, prereq_title, pre) values (‘IS201’, ‘System Analysis’, null)
2010/03/30 21
Content of file Fj for associated objectsupdate sectionset taught_by = (select {oid} from instructor where Instructor_name = ‘A.B.ADAM’)set divided_by = (select {oid} from course where course = ‘IS101’)set provided_by = (select {oid} from enrol where Instructor_name = ‘A.B.ADAM’ and course=‘IS101’)where course = ‘IS101’ and section# = 1
update sectionset taught_by = (select {oid} from instructor where instructor_name = ‘J.S.FINK’)set divided_by = (select {oid} from course where course = ‘IS101’)set provided_by = (select {oid} from enrol where Instructor_name = ‘J.S.FINK’ and course=‘IS101’)where course = S101’ and section# = 2)
update enrolset register_by = (select {oid} from graduate_student where student# = ‘012888’)set provide_by = (select {oid} from section where Instructor_name = ‘A.B.ADAM’ and course = ‘IS101’ and section# =1)where ss# = 415223641 and course = S101’ and section = 1 and year = 1995
update enrolset register_by = (select {oid} from graduate_student where student# = ‘120008’)set provide_by = (select {oid} from section where instructor_name = ‘J.S.FINK’ and course = ‘IS101’ and section# = 2)where course = ‘IS101’ and section = 2 and year = 1996
update courseset pre_by = (select {oid} from prerequisite where course = ‘IS301’)where prerequisite = ‘IS301’
update prerequisiteset prereq = (select {oid} from course where course = ‘IS301’)where prerequisite = ‘IS201’
2010/03/30 22
Content of file Fk for subclass objectsContent of file Fk for subclass objects
update graduate_student
set student_name = (select Student_name from student where student# = ‘012888’)
set sex = (select Student_sex from student where student# = ‘012888’)
where student# = ‘012888’
update graduate_student
set student_name = (select Student_name from student where student# = ‘120008’)
set sex = (select Student_sex from student where student# = ‘1200008’)
where student# = ‘1200008’
2010/04/02 23
Record COURSE
OID COURSE# COURSE_LOCATION COURSE-TITLE LOCATION
{001}
{002}
{003}
IS101
IS201
IS301
LECTURE THEATRE 1
LECTURE THEATRE 2
ROOM P7818
INTRO TO COMPUTER SCIENCE
SYSTEM ANALYSIS
DECISION SUPPORT SYSTEM
LECTURE THEATRE 1
LECTURE THEATRE 2
ROOM P7818
Record PREREQUSITE
OID PREREQUISITE# PREREQUISITE_TITLE STORED_OID
{014} IS201 SYSTEM ANALYSIS {003}
Record GRADUATE_STUDENT
OID STUDENT# DEGREE_TO_BE Student_name Sex
{004}
{005}
012880
120008
M.PHIL
PH.D
Paul Chitson
Irene Kwan
M
F
Record INSTRUCTOR
OID INSTRUCTOR_NAME INSTRUCTOR_ADDRESS
{007}
{008}
{009}
A.B. ADAMS
J.S. FINK
A.M. JONES
WHITE PLAINS
BROOKLYN
LONG ISLAND
Record SECTION
OID SECTION# HOURS STORDED_OID STORED_OID STORED_OID
{010}
{011}
SECTION 1
SECTION 2
30
30
{001}
{001}
{007}
{008}
{012}
{013}
Record STUDENT
OID STUDENT# STUDENT_NAME SEX
{004}
{005}
{006}
012880
120008
117402
PAUL CHITSON
IRENE KWAN
JOHN LEE
M
F
M
Record ENROL
OID INSTRUCTOR_NAME SECTION# COURSE# STUDENT# GRADE YEAR STORED_OID STORED_OID
{012}
{013}
A.B. ADAMS
J.S. FINK
Section 1
Section 2
CS101
CS101
025056
312788
A
P
1995
1996
{010}
{011}
{004}
{005}
Converted Object-Oriented Database
2010/03/30 24
DATA CONVERSION FROM RELATIONAL TO XML DOCUMENT BY USING INTERPRETIVE TRANSFORMER APPROACH
Begin While not end of element do Read an element from the translated target DTD; Read the tuple of a corresponding relation of the element from the source relational database; load this tuple into a target XML document; read the child elements of the element according to the DTD; while not at end of the corresponding child relation in the
source relational database do
read the tuple from the child relation such that the child’s corresponding to the processed parent relation’s tuple;
load the tuple to the target XML document; end while //end inner loop end while // end outer loopend
2010/03/30 25
Rule 1: Mapping weak entity from RDB to XML
Relational Schema
Relation A(A1, A2)Relation B(*A1, B1, B2)
Schema
Translation
DTD
<!ELEMENT A(B)*><!ATTLIST A A1 CDATA #REQUIRED><!ATTLIST A A2 CDATA #REQUIRED><!ATTLIST A id ID #REQUIRED><!ELEMENT B EMPTY><!ATTLIST B B1 CDATA #REQUIRED><!ATTLIST B B2 CDATA #REQUIRED><!ATTLIST B idref IDREF #REQUIRED>
DTD Graph
A1
id
Element A
Element B
*
A2
idref
B2
B1
Entity A
R
A1A2
A1B1B2
1
n
Entity B
EER Model
Data
Conversion
Relation AA1
a11
a12
A2
a21
a22
Relation B*A1
a11
B1
b11
B2
b21
<A A1="a11" A2="a21" id="1"> <B B1="b11" B2="b21" idref="1"></B></A>
<A A1="a12" A2="a22" id="2"></A>
XML Document
2010/03/30 26
Rule 2: Mapping cardinality from RDB to XML
Case 1:
Relational Schema
Relation A(A1, A2)Relation B(B1, B2, *A1)
DTD
<!ELEMENT A(B)><!ATTLIST A A1 CDATA #REQUIRED><!ATTLIST A A2 CDATA #REQUIRED><!ELEMENT B EMPTY><!ATTLIST B B1 CDATA #REQUIRED><!ATTLIST B B2 CDATA #REQUIRED>
Schema
Translation
Entity A
Entity B
R
A1A2
B1B2
1
1
EER Model
A1
A2
B1
B2
Element A
Element B
DTD Graph
b12 b22 a12
<A A1="a11" A2="a21"> <B B1="b11" B2="b21"></B></A>
<A A1="a12" A2="a22"> <B B1="b12" B2="b22"></B></A>
Relation AA1
a11
a12
XML DocumentA2
a21
a22
Relation BB1
b11
B2
b21
*A1
a11
Data
Conversion
2010/03/30 27
Rule 2: Mapping cardinality from RDB to XML
Case 2:
Relational Schema
Relation A(A1, A2)Relation B(B1, B2, *A1)
DTD
<!ELEMENT A(B)*><!ATTLIST A A1 CDATA #REQUIRED><!ATTLIST A A2 CDATA #REQUIRED><!ELEMENT B EMPTY><!ATTLIST B B1 CDATA #REQUIRED><!ATTLIST B B2 CDATA #REQUIRED>
Schema
Translation
Entity A
Entity B
R
A1A2
B1B2
1
n
EER Model
A1
A2
B1
B2
Element A
Element B
*
DTD Graph
b12 b22 a12
<A A1="a11" A2="a21"> <B B1="b11" B2="b21"></B></A>
<A A1="a12" A2="a22"> <B B1="b12" B2="b22"></B> <B B1="b13" B2="b23"></B></A>
Relation AA1
a11
a12
XML DocumentA2
a21
a22
Relation BB1
b11
B2
b21
*A1
a11
Data
Conversion
b13 b23 a12
2010/03/30 28
Rule 2: Mapping cardinality from RDB to XML
Case 3:
Entity A
Entity B
R
A1A2
B1B2
m
n
Relational Schema
Relation A(A1, A2)Relation B(B1, B2)Relation R(*A1, *B1)
A1
A2
B1
B2Element A Element B
Element X
Element R
DTD
<!ELEMENT A EMPTY><!ATTLIST A A1 CDATA #REQUIRED><!ATTLIST A A2 CDATA #REQUIRED><!ATTLIST A A_id ID #REQUIRED><!ELEMENT R EMPTY><!ATTLIST R A_idref IDREF #REQUIRED><!ATTLIST R B_idref IDREF #REQUIRED><!ELEMENT B EMPTY><!ATTLIST B B1 CDATA #REQUIRED><!ATTLIST B B2 CDATA #REQUIRED><!ATTLIST B B_id ID #REQUIRED>
Schema
Translation
EER Model DTD Graph
A_idref B_idref
A_id B_id
<A A1="a11" A2="a21" A_id="1"></A><B B1="b11" B2="b21" B_id="2"></B><R A_idref="1" B_idref="2"></R>
<A A1="a12" A2="a22" A_id="3"></A><B B1="b12" B2="b22" B_id="4"></B><R A_id="3" B_idref="4"></R>
XML Document
Data
Conversionb12 b22
Relation AA1
a11
a12
A2
a21
a22
Relation BB1
b11
B2
b21
a12 b12
Relation R*A1
a11
*B1
b11
2010/03/30 29
Rule 3: Mapping aggregation from RDB to XMLEntity A
R2
A1A2
1
n
Entity CC1C2
Entity B R1m nB1
B2
Relational Schema
Relation A(A1, A2)Relation B(B1, B2)Relation C(C1, C2)Relation R1(*B1, *C1, *A1)
EER Model
Schema
TranslationDTD
<!ELEMENT A(Group)+><!ATTLIST A A1 CDATA #REQUIRED><!ATTLIST A A2 CDATA #REQUIRED><!ELEMENT Group(B, R1, C)><!ELEMENT B EMPTY><!ATTLIST B B1 CDATA #REQUIRED><!ATTLIST B B2 CDATA #REQUIRED><!ATTLIST B B_id ID #REQUIRED><!ELEMENT R1 EMPTY><!ATTLIST R1 B_idref IDREF #REQUIRED><!ATTLIST R1 C_idref IDREF #REQUIRED><!ELEMENT C EMPTY><!ATTLIST C C1 CDATA #REQUIRED><!ATTLIST C C2 CDATA #REQUIRED><!ATTLIST C C_id ID #REQUIRED>
B1
B2
C1
C2Element B Element C
Element Group
Element R1
Element AA1
A2
DTD Graph
B_idref C_idref
B_id C_id
+
b12 b22
Relation AA1
a11
a12
A2
a21
a22
Relation BB1
b11
B2
b21
Data
Conversion
c12 c22
Relation CC1
c11
C2
c21
a12b12
Relation R1*A1
a11
*B1
b11
c12
*C1
c11
<A A1="a11" A2="a21"> <Group> <B B1="b11" B2="b21" B_id="1"></B> <R1 B_idref="1" C_idref="2"></R1> <C C1="c11" C2="c21" C_id="2"></C> </Group></A>
<A A1="a12" A2="a22"> <Group> <B B1="b12" B2="b22" B_id="3"></B> <R1 B_idref="3" C_idref="4"></R1> <C C1="c12" C2="c22" C_id="4"></C> </Group></A>
XML Document
2010/03/30 30
Rule 4: Mapping ISA relationship from RDB to XML
Relational Schema
Relation A(A1, A2)Relation B(*A1, B1)
Entity A
Entity B
isa
A1A2
A1B1
DTD
<!ELEMENT A(B)?><!ATTLIST A A1 CDATA #REQUIRED><!ATTLIST A A2 CDATA #REQUIRED><!ELEMENT B EMPTY><!ATTLIST B B1 CDATA #REQUIRED>
EER Model
Schema
Translation
DTD Graph
A1
A2
B1
Element A
Element B
?
Relation AA1
a11
a12
A2
a21
a22
Relation B*A1
a11
B1
b11
Data
Conversion
<A A1="a11" A2="a21"> <B B1="b11" ></B></A>
<A A1="a12" A2="a22"></A>
XML Document
2010/03/30 31
Rule 5: Mapping generalization from RDB to XMLCase 1:
Entity AA1A2
Entity CA1C1
Entity BA1B1
d
Relational Schema
Relation A(A1, A2)Relation B(*A1, B1)Relation C(*A1, C1)
B1 C1
A1
A2Element A
Element CElement B
|
DTD
<!ELEMENT A(B | C)><!ATTLIST A A1 CDATA #REQUIRED><!ATTLIST A A2 CDATA #REQUIRED><!ELEMENT B EMPTY><!ATTLIST B B1 CDATA #REQUIRED><!ELEMENT C EMPTY><!ATTLIST C C1 CDATA #REQUIRED>
EER Model DTD Graph
Schema
Translation
<A A1="a11" A2="a21"> <B B1="b11"></B> </A>
<A A1="a12" A2="a22"> <C C1="c11"></C></A>
Relation AA1
a11
a12
XML DocumentA2
a21
a22
Relation B*A1
a11
B1
b11
Data
Conversion
Relation C*A1
a12
C1
c11
2010/03/30 32
Rule 5: Mapping generalization from RDB to XMLCase 2: Overlap Generalization
Entity AA1A2
Entity CA1C1
Entity BA1B1
o
Relational Schema
Relation A(A1, A2)Relation B(*A1, B1)Relation C(*A1, C1)
B1 C1
A1
A2Element A
Element CElement B
?
DTD
<!ELEMENT A(B?, C?)><!ATTLIST A A1 CDATA #REQUIRED><!ATTLIST A A2 CDATA #REQUIRED><!ELEMENT B EMPTY><!ATTLIST B B1 CDATA #REQUIRED><!ELEMENT C EMPTY><!ATTLIST C C1 CDATA #REQUIRED>
EER Model DTD Graph
Schema
Translation
Relation AA1
a11
a12
A2
a21
a22
Relation B*A1
a11
B1
b11
Data
Conversion
Relation C*A1
a11
C1
c11
a12 c12
<A A1="a11" A2="a21"> <B B1="b11"></B> <C C1="c11"></B> </A>
<A A1="a12" A2="a22"> <C C1="c12"></C></A>
XML Document
2010/03/30 33
Rule 6: Mapping n-ary relationship from RDB to XML
Relational Schema
Relation A(A1, A2)Relation B(B1, B2)Relation C(C1, C2)Relation R(*A1, *B1, *C1)
Entity CC1C2
Entity BB1B2
Entity AA1A2
Rm:n
m:n
m : n
B1
A1
A2
C1
C2Element A Element C
Element Group
Element B
B2
DTD
<!ELEMENT Group(A, B, C)><!ELEMENT A EMPTY><!ATTLIST A A1 CDATA #REQUIRED><!ATTLIST A A2 CDATA #REQUIRED><!ELEMENT B EMPTY><!ATTLIST B B1 CDATA #REQUIRED><!ATTLIST B B2 CDATA #REQUIRED><!ELEMENT C EMPTY><!ATTLIST C C1 CDATA #REQUIRED><!ATTLIST C C2 CDATA #REQUIRED>
EER Model DTD Graph
Schema
Translation
b12 b22
Relation AA1
a11
a12
A2
a21
a22
Relation BB1
b11
B2
b21
Data
Conversion
c12 c22
Relation CC1
c11
C2
c21
c12a12
Relation R*C1
c11
*A1
a11
b12
*B1
b11
<Group> <A A1="a11" A2="a21"></A> <B B1="b11" B2="b21"></B> <C C1="c11" C2="c21"></C></Group>
<Group> <A A1="a12" A2="a22"></A> <B B1="b12" B2="b22"></B> <C C1="c12" C2="c22"></C></Group>
XML Document
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Case Study:Convert the following relational database into an XML
document
AB
D
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Schema translation
Department
Trip
Car Rental
Department_IDSalary
Trip_ID
Car ModelStaff_ID
*
*
Department
Trip
Car Rental
Department_IDSalary
Trip_ID
Car ModelStaff_ID
R1
R2
1
1
n
n
===============è
Entity Relationship Model DTD Graph
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Mapped XML document
<ROOT><DEPARTMENT DEPARTMENT_ID = “AA001” SALARY = ‘35670”>
<TRIP TRIP_ID = “T0001”><CAR_RENTAL CAR_MODEL=”MZ-18” STAFF_ID=”A002”/><CAR_RENTAL CAR_MODEL=”R_023” STAFF_ID=”B004”/><CAR_RENTAL CAR_MODEL=”SA_01” STAFF_ID=”A002”/>
</TRIP><TRIP TRIP_ID = “T0002”>
<CAR_RENTAL CAR_MODEL=”MZ-38” STAFF_ID=”B001”/></TRIP>
</DEPARTMENT><DEPARTMENT DEPARTMENT_ID = “AB001” SALARY = ‘30010”>
<TRIP TRIP_ID = “T0003”><CAR_RENTAL CAR_MODEL=”SA-38” STAFF_ID=”A001”/>
</TRIP></DEPARTMENT><DEPARTMENT DEPARTMENT_ID = “AB001” SALARY = ‘30010”> <TRIP TRIP_ID = “T0004”>
<CAR_RENTAL CAR_MODEL=”R-023” STAFF_ID=”C001”/> </TRIP></DEPARTMENT>
</ROOT>
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Lecture Summary
Schema translation must be done before data conversion. In converting relational database into object-oriented database, OID and Stored OID must be mapped from parent and child relations. In converting relational database into XML document, the parent child relations must be mapped into the hierarchical structure of XML document.
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Review question 11
What is the advantage of logical level data conversion when compared with physical level data conversion?
What is the procedure of converting a relational database into an XML document?
What is the procedure of converting an XML document into a relational database?
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Make-up Tutorial question 11Convert the following relational database into an XML document based on the selection of XML view on Department:Relation Car
Car_modelSize Description
SA-38 165 Long car (Douglas)
MZ-18 120 Small sportier
R-023 150 Long car (Rover)
Relation Car_rental
Car_modelStaff_ID *Trip_ID
MZ-18 A002 T0001
MZ-18 B001 T0002
R-023 B004 T0001
R-023 C001 T0004
SA-38 A001 T0003
SA-38 A02 T0001
Relation Trip
Trip_ID*Department_ID
T0001 AA001
T0002 AA001
T0003 AB001
T0004 BA001
Relation Department
*Department_IDSalary
AA001 35670
AB001 30010
BA001 22500
Relation People
Staff_IDName DOB
A001 Alexander 07/01/1962
A002 April 05/24/1975
B001 Bobby 12/06/1984
B002 Bladder 01/03/1980
B003 Brent 12/15/1979
B004 Belandar 08/18/1963
C001 Calvin 04/03/1977
C002 Chevron 02/02/1974
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Reading Assignment
Chapter 4 Data Conversion of “Information Systems Reengineering and Integration” by Joseph Fong, Springer Verlag, 2006.
