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Association Relationship Transformation of XML Schemas to Object–Relational Databases

Association Relationship Transformation of XML Schemas to Object–Relational Databases. Bandung, 11 September 2002. Nathalia Devina Widjaya, David Taniar Wenny Rahayu, Eric Pardede. Structure of Presentation. Background Objectives Association Relationship Related Work

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Association Relationship Transformation of XML Schemas to Object–Relational Databases

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  1. Association Relationship Transformation of XML Schemas to Object–Relational Databases Bandung, 11 September 2002 Nathalia Devina Widjaya, David Taniar Wenny Rahayu, Eric Pardede

  2. Structure of Presentation • Background • Objectives • Association Relationship • Related Work • Proposed Transformation Methodology • Conclusion and Future Work

  3. 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.

  4. 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

  5. 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

  6. 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

  7. 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

  8. 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

  9. 1 HAS 1 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

  10. 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 … <complexType> <sequence> <element ref=”office” minOccurs=”0” maxOccurs= “1” /> <element ref=”lecture” minOccurs=”0” maxOccurs=“unbounded”/> </sequence> …

  11. One-to-One Relationship (3) • … • </element> • <element name = “office”> • <attribute name = “officeid” type = “string” use = “required”/> • </element>… CREATE OR REPLACE TYPE Office_T AS OBJECT (office_id VARCHAR2(10));

  12. 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 <element name = “lecture”> … <attribute name = “lectureid” type = “string” use = “required” /> <attribute name = “lectureName” type = “string” use = “optional” />… CREATE OR REPLACE TYPE Lecture_T AS OBJECT (lecture_id VARCHAR2 (10), lecture_name VARCHAR2 (50), lecture_office REF office_T)

  13. 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));

  14. 1 HAS * One-to-Many Relationship • The example that is used in this section is the relationship between customer and order

  15. 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 <xs:element name = “customer” type = “customerType” / > … <xs:complexType name = “customerType”> … </xs:complexType>

  16. One-to-Many Relationship (3) • <xs:complexType name = “customerType”> • <xs:attribute name = “customerName” type=“xs:string”/> • <xs:attribute name = “shippingAddress” type=”xs:string”/> • <xs:attribute name = “shippingCity” type=”xs:string”/> • <xs:attribute name = “shippingState” type=”xs:string”/> • <xs:attribute name = “shippingPostalCode” • type=”xs:integer”/> • </xs:complexType>… • 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)

  17. 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 • … • <xs:sequence> • <xs:element name = “order” type= “ orderType” • minOccurs= “1” max Occurs = “unbounded” / > • … • <xs:complexType name = “orderType”> • …

  18. One-to-Many Relationship (5) … <xs:complexType name = “orderType”> <xs:attribute name =”orderID” type=”xs:integer”/> <xs:attribute name = “orderDate” type= “xs:date”/> </xs:complexType> CREATE OR REPLACE TYPE Order_T AS OBJECT (order_id VARCHAR2(10), order_date DATE, order_customer REF Customer_T)

  19. 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));

  20. * ENROLLS_IN * Many-to-Many Relationship • The example that is used is the relationship between student and course

  21. 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 … <xs:complexType> <xs:sequence> <xs:element name = “students” minOccurs =”1” maxOccurs =“unbounded”> <xs:complexType> … <xs:element name = “course” minOccurs =”1” maxOccurs = “unbounded”> <xs:complexType> …

  22. Many-to-Many Relationship (3) <xs:element name = “student”>… <xs:attribute name =”refCourseID” type= “xs:string” />… <xs:attribute name = “studentid” type = “xs:string” />… … <xs:element name = “course”>… <xs:attribute name =”refstudentID” type= “xs:string” />… <xs:attribute name = “courseid” type = “xs:string” />… … 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))

  23. 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 • … • <xs:attribute name =”refCourseID” type= “xs:string” />… • … • <xs:attribute name =”refstudentID” type= “xs:string” />… 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));

  24. 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);

  25. 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

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