Association Relationship Transformation of XML Schemas to ObjectRelational Databases

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Association Relationship Transformation of XML
Schemas to ObjectRelational Databases
Bandung, 11 September 2002

• Nathalia Devina Widjaya, David Taniar
• Wenny Rahayu, Eric Pardede

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Structure of Presentation

• Background
• Objectives
• Association Relationship
• Related Work
• Proposed Transformation Methodology
• Conclusion and Future Work

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Background

• The popularity of XML is growing and is gradually
  accepted as the standard for describing and
  interchanging data between various systems and
  databases on the Internet
• XML now offers XML Schema definition language as
  a substitution of DTD. It provides richer
  facilities for defining and constraining the
  content of XML documents
• With the wide acceptance of the OO conceptual
  models, more systems are modeled and expressed
  with OO notation. This situation suggests the
  necessity to integrate the OO conceptual models
  and XML.

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Objectives

• The goal of this work is to present a coherent
  way to transform the XML schema into ORDB using
  Oracle 9i features models
• This transformation is important so that all the
  data that are created using XML schema can be
  transformed to the database using Oracle format
  and features, without eliminating the object
  relational features

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Objectives (2)

• The emphasis of this paper is on the
  transformation of association relationship to
  help people conveniently generate Oracle database
• The work presented in this paper is actually part
  of a larger research project on Transformation
  from XML Schema to Object-Relational Databases.
• (i) transformation of aggregation and
  inheritance relationship from XML Schema to ORDB
• (ii) transformation of association relationship
  from XML Schema to ORDB

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Association Relationship

• ORDB was introduced to improve RDB performance
  and has become popular because it improves the
  limitations of RDB such as lack of support for
  new types and composite data values
• Since ORDB has OO features, it encapsulates the
  static (including association relationship) as
  well as dynamic aspects of objects
• The association relationship represents a
  connection between object instances. Basically,
  it is a reference from one object to another that
  provides access paths among objects in a system.
• The objects are connected through an association
  link. The link can have a specified cardinality
  one-to-one, one-to-many, many-to-many

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Related Work

• Most existing work has focused on methods to map
  RDB to an XML database for database
  interoperability. Some works still used DTD and
  some have used XML schema.
• The previous works include mapping referential
  integrity constraints from RDB to XML, semantic
  data modeling using XML schemas, hybrid database
  schema to map a subset of XML documents onto
  database structures, generic-transforming rules
  from the OOCM to XML schema, etc.
• The transformation of generalization and
  aggregation relationship from the XML Schema to
  ORDB has been done earlier as a first part of the
  project

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Proposed Transformation Methodology

• There are 3 parts of association relationships
  that will be transformed, one-to-one association,
  one-to-many association and many-to-many
  association
• The method that we use to implement the
  association relationship in Oracle is using
  object references (REF). Instead of connecting
  two tables through the values of the associated
  primary key and foreign key, this method allows
  one to directly connecting two tables through
  referencing attribute

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One-to-One Relationship

• The example that is used in this section is the
  relationship between lecturer and office
• For one-to-one association relationship, it is
  important to determine the participation of the
  objects to decide location of the foreign keys in
  relational system

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One-to-One Relationship (2)

• The Transformation steps
• 1. From the XML Schema, element with partial
  participation will be recognized by statement
  minOccurs 0 maxOccurs 1 . First, create an
  object for the one with partial participation
  (office) with its attributes

ltcomplexTypegt ltsequencegt ltelement refoffice
minOccurs0 maxOccurs 1 /gt ltelement
reflecture minOccurs0 maxOccursunbounded/
gt lt/sequencegt
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One-to-One Relationship (3)
lt/elementgt ltelement name officegt
ltattribute name officeid type string use
required/gt lt/elementgt
CREATE OR REPLACE TYPE Office_T AS OBJECT
(office_id VARCHAR2(10))
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One-to-One Relationship (4)
2. Create another object for the one with total
participation, lecture, with the attributes and a
REF that refers to office type
ltelement name lecturegt ltattribute name
lectureid type string use required
/gt ltattribute name lectureName type
string use optional /gt
CREATE OR REPLACE TYPE Lecture_T AS OBJECT
(lecture_id VARCHAR2 (10),
lecture_name VARCHAR2 (50),
lecture_office REF office_T)
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One-to-One Relationship (5)
3. Lastly, we create one table for Lecture and
another one for Office. Each table has its id
as well as the constraints
CREATE TABLE Office OF Office_T (office_id NOT
NULL, PRIMARY KEY (office_id)) CREATE TABLE
Lecture OF Lecture_T (lecture_id NOT NULL,
PRIMARY KEY (lecture_id))
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One-to-Many Relationship

• The example that is used in this section is the
  relationship between customer and order

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One-to-Many Relationship (2)

• The Transformation steps
• 1. An element with a complex type in XML Schema,
  which does not have reference inside it, is
  transformed by creating an object in ORDB with
  all the attributes

ltxselement name customer type
customerType / gt ltxscomplexType name
customerTypegt lt/xscomplexTypegt
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One-to-Many Relationship (3)
ltxscomplexType name customerTypegt ltxsattribu
te name customerName typexsstring/gt ltxsat
tribute name shippingAddress
typexsstring/gt ltxsattribute name
shippingCity typexsstring/gt ltxsattribute
name shippingState typexsstring/gt ltxsattr
ibute name shippingPostalCode
typexsinteger/gt lt/xscomplexTypegt
CREATE OR REPLACE TYPE Customer_T AS OBJECT
(customer_id VARCHAR2 (10),
customer_name VARCHAR2 (50),
shipping_address VARCHAR2 (100),
shipping_city VARCHAR2 (20),
shipping_state VARCHAR2 (20),
shipping_postalcode NUMBER)
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One-to-Many Relationship (4)
2. For another element in the complex type that
has reference to another element, create another
object and write all the attributes. The
minOccurs 1 and maxOccurs unbounded in
XML will be shown by using REF in Oracle
ltxssequencegt ltxselement name order type
orderType minOccurs 1 max Occurs
unbounded / gt ltxscomplexType name
orderTypegt
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One-to-Many Relationship (5)
ltxscomplexType name orderTypegt ltxsattribut
e name orderID typexsinteger/gt ltxsattribut
e name orderDate type xsdate/gt lt/xscomple
xTypegt
CREATE OR REPLACE TYPE Order_T AS OBJECT
(order_id VARCHAR2(10), order_date DATE,
order_customer REF Customer_T)
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One-to-Many Relationship (6)
3. Lastly, create a table for each type. Each
table has its id as well as the constraints
CREATE TABLE Customer OF Customer_T
(customer_id NOT NULL, PRIMARY KEY
(customer_id)) CREATE TABLE Order OF Order_T
(order_id NOTNULL, PRIMARY KEY (order_id))
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Many-to-Many Relationship

• The example that is used is the relationship
  between student and course

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Many-to-Many Relationship (2)

• The Transformation steps
• 1. All elements name that has minOccurs 1 max
  Occurs unbounded need to be created as object
  in ORDB and write all its attributes

ltxscomplexTypegt ltxssequencegt ltxselement
name students minOccurs 1 maxOccurs
unboundedgt ltxscomplexTypegt ltxselement
name course minOccurs 1 maxOccurs
unboundedgt ltxscomplexTypegt
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Many-to-Many Relationship (3)
ltxselement name studentgt ltxsattribute name
refCourseID type xsstring
/gt ltxsattribute name studentid type
xsstring /gt ltxselement name
coursegt ltxsattribute name refstudentID
type xsstring /gt ltxsattribute name
courseid type xsstring /gt
CREATE OR REPLACE TYPE Student_T AS Object
(student_id VARCHAR2 (10),
student_name VARCHAR2(30)) CREATE OR REPLACE
TYPE Course_T AS Object (course_id VARCHAR2(10
), course_name VARCHAR2(30))
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Many-to-Many Relationship (4)
2. In the XML Schema, each element will be linked
to another element by using the attribute name
that refers to another element ID. For those
elements create table for each of them in ORDB
and add the constraints for the attributes
ltxsattribute name refCourseID type
xsstring /gt ltxsattribute name
refstudentID type xsstring /gt
CREATE TABLE Student OF Student_T
(student_id NOT NULL, PRIMARY
KEY(student_id)) CREATE TABLE Course OF
Course_T (course_id NOT NULL, PRIMARY KEY
(order_id))
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Many-to-Many Relationship (5)
3. Create another table to keep the relationship
between the two connected tables in ORDB. This
table will have reference to the participating
objects
CREATE TABLE Enrolls_in (student REF
Student_T, course REF Course_T)
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Conclusion and Future Work

• In this paper, we have investigated the
  transformation from XML schema to the ORDB by
  using Oracle 9i, emphasis the transformation of
  association relationship
• This transformation is important because people
  tends to eliminate the object-oriented conceptual
  features when they transform XML schema to the
  database.
• Our future work is being planned to investigate
  more transformation from XML schema to ORDB for
  other XML Schema features that has not been
  discussed in this paper. Further research should
  be done to create a query from XML schema to get
  the data from the Oracle 9i databases