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Applications of ORA-SS:Applications of ORA-SS:

An Object-Relationship-Attribute Model for Semistructured DataAn Object-Relationship-Attribute Model for Semistructured Data

Tok Wang Ling1

Mong Li Lee1

Gillian Dobbie2

1Department of Computer Science, National University of Singapore2Department of Computer Science, The University of Auckland, NZ

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ContentContent Part I ORA-SS: An Object-Relationship-Attribute

Model for Semistructured Data– Object class– Relationship Type– Attribute– Semistructured data instance– Functional dependencies and other constraints– Inheritance hierarchy

Part II Research Topics using ORA-SS Model– Normal form ORA-SS schema diagram– Storage schema for ORA-SS/XML databases– ORA-SS/XML views– Evaluating XML queries on ORA-SS databases– Translating relational schema into ORA-SS schema– Integration of XML documents

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MotivationMotivation

(a) OEM Diagram

Figure 1: Sample instance demonstrating OEM and dataguide

(B) Dataguide

▼♦ department

▼♦ student

▼♦ course

♦ name ♦ number

♦ student number ♦ name ♦ grade

♦ number ♦ name

department

cs

student

number name

computer science

&3

&1

course course

number

&20

name

&21 &22

number

grade

1234 B.Y.Smith 70 1235 C.U. Brown 60

cs4221 Database

&26

&7

student

&4

&2

name

&5

student

&6

student number

&23

name

&24

grade

&25

studentnumber

name

&27 &28

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Motivation (cont.)Motivation (cont.)

Student

Figure 2: ORA-SS instance diagram

Figure 3: ORA-SS schema diagram

Name: Computer

Science course course

Number: CS

department

Number:CS4221

Name:Database

student

Studentnumber:1234

Name:B.Y. Smith

Grade:70

student

Studentnumber:1235

Name:C.U. Brown

Grade:60

NumberName

studentnumber

department

course2, 1:n, 1:1

studentnumber name

name grade

cs

number namecs

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ORA-SSORA-SS

The Data ModelThe Data Model Object class

– attributes of object class– ordering on object class

Relationship Type– attributes of relationship type– degree of n-ary relationship type– participation of objects in relationship type– disjunctive relationship type– recursive relationship type– symmetric relationship type

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ORA-SSORA-SS

The Data Model (cont.)The Data Model (cont.) Attribute

– key attribute– degree of n-ary relationship type– composite attribute– disjunctive attribute– attributes with unknown structure– ordering on attribute– fixed and default values of attribute– derived attribute

Semistructured data instance

Functional dependencies and other constraints

Inheritance hierarchy

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The data model of ORA-SSThe data model of ORA-SS

Object ClassObject Class

student

number first name last nameFigure 4: Object class student with attributes

in an ORA-SS schema diagram

–attributes of object class

–ordering on object class

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The data model of ORA-SSThe data model of ORA-SS Relationship TypeRelationship Type– attributes of relationship type– degree of n-ary relationship type– participation of objects in relationship type– disjunctive relationship type– recursive relationship type– symmetric relationship typeproject

id namemember

name job title publication

number title

2, +, +

2, *, +

(a) ORA-SS Schema Diagram (b) Instance Relationship

♦ number ▼♦ publication

▼♦ project

▼♦ member ♦ name

♦ title

♦ job title

♦ name ♦ id

(c) Dataguide

Figure 5: Representing binary relationship type

p1

p2

p3

m1

m2

pub1

pub2

pub3

project member publication

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The data model of ORA-SSThe data model of ORA-SS

Relationship Type (cont.)Relationship Type (cont.)

project

id namemember

name job title publication

number title

2, +, +

3, *, +

(a) ORA-SS Schema Diagram

(b) Instance Relationship

(c) Dataguide

Figure 6: Representing ternary relationship type

p1

p2

p3

m1

m2

pub1

pub2

pub3

project member publication

♦ number ▼♦ publication

▼♦ project

▼♦ member ♦ name

♦ title

♦ job title

♦ name ♦ id

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The data model of ORA-SSThe data model of ORA-SS AttributeAttribute– key attribute– degree of n-ary relationship type– composite attribute– disjunctive attribute– attribute with unknown structure– ordering on attribute– fixed and default values of attribute– derived attribute

hobby

course

student*codetitle ANY

dept prefixD: comp

number *studentnumber

firstname

lastname

mark grade

cs cs

cs2, 4:n, 3:8

Figure 7: Object classes with relationship type and attributes in an ORA-SS schema diagram

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The data model of ORA-SSThe data model of ORA-SS OrderingOrdering

– the instances of an object class can be ordered,– the values of an attribute can be ordered, and– the set of attributes of an object class can be ordered

book

* content

chapter

paragraph

title author

preface toc

text

2, 1:1, 1:1<

<cc,3, 1:n, 1:1

4, 1:n, 1:1

Figure 8: Ordered object classes and attributes in an ORA-SS schema diagram

<

<

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The data model of ORA-SSThe data model of ORA-SS DisjunctionDisjunction

– disjunctive object class, and– disjunctive attribute.

Figure 9: Disjunctive attribute and relationship type in an ORA-SS schema diagram

code

numberstreetname

course

title

examvenue

lecture theatre laboratorystudent

hostel home

studentnumber

name grade

name

cs,2, 4:n, 3:8

address, 2, ?, +

cs

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The data model of ORA-SSThe data model of ORA-SS ReferencesReferences

Figure 10: Referencing an object class in an ORA-SS Schema Diagram

course

studentcode title

grade

student

faculty

facultyname

fs,2, 1:n, 1:n

*fs,

facultygradehistory

hostel home

cs,2, 4:n, 3:8

streetnumber

coursecode

student number

grade

name

cs

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The data model of ORA-SSThe data model of ORA-SS References (cont.)References (cont.)

course

code title course

2, 0:5, 1:n

Figure 11: Example of a recursive relationship type in an ORA-SS Schema Diagram

cs

course

studentcoursenumber

numberof students

cs,2, +, +

student

coursestudentnumber

name

2, +, +

grade

Figure 12: Symmetric relationship types in an ORA-SS schema diagram

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The data model of ORA-SSThe data model of ORA-SS Reference (cont.)Reference (cont.)

Figure 13: ORA-SS schema diagram

sct

student

name course

sc,2, 3:8, 4:n

code title grade

sc

tutor

sct,3, 1:1, 1:n

name office feedback

hostel home

name number street

tutor

ct,2, +, +

ct

hours

building room

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The data model of ORA-SSThe data model of ORA-SS Reference (cont.)Reference (cont.)

Figure 14: ER diagram of schema in Figure 13.

student sc course

ctfeedback sct hours

tutor

name office

building room

hostel home

name number street

name grade code title

3:8 4:n

1:11:n

1:n1:n

UNION

addressta

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The data model of ORA-SSThe data model of ORA-SS Functional DependenciesFunctional Dependencies

student, course tutor

tutor course

1/n

n/1n/_student course

tutor

sct

Figure 15: Functional dependencies diagram

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The data model of ORA-SSThe data model of ORA-SS Inheritance HierarchyInheritance Hierarchy

staffnumber

studentnumber

3,+,+3,+,+gradetitle

sc,2,+,+student

number

course

student

faculty tutor

ssn ssn payratedegree

(a) ORA-SS Schema Diagram

staffnumber

person

payratedegree

student

tutor

ssn

studentnumber

faculty

(b) Inheritance Diagram

Figure 16: ORA-SS schema diagram and inheritance diagram

ssn

Studentnumber

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The data model of ORA-SSThe data model of ORA-SS ConstraintsConstraints Inclusion dependency Semantic dependencies

(a) Date of employee joined company (b) Date of employee joined department

Figure 17: Modeling join date (jdate) ORA-SS schema diagram

ed,2,1:1,1:n

jdatenamessn

department

employee

?

departmentnumber

ed

name2,1:1,1:n

jdatenamessn

department

employee

?

departmentnumber

name

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Research Topics for ORA-SS ModelResearch Topics for ORA-SS Model Normal form ORA-SS schema diagram

– remove redundant data– resolve class hierarchy conflicts

Storage schema for ORA-SS/XML databases– use Object Relational Model

ORA-SS/XML Views– derived information from references and class hierarchy– defining views– materialized view maintenance– view updates

Evaluating XML queries on ORA-SS databases– XML schema to ORA-SS Schema– XML document to ORA-SS database

Translating relational schema into ORA-SS schema Integration of XML documents

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Research Topics for ORA-SS ModelResearch Topics for ORA-SS Model Normal Form ORA-SS Schema DiagramNormal Form ORA-SS Schema Diagram Schema may have a lot of redundant data Update anomalies Normal Form schema is needed

titleauthorISBN

2

2

professor

textbook

staff#name

course

C.Code title

+

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Research Topics for ORA-SS ModelResearch Topics for ORA-SS Model NF ORA-SS Schema Diagram (cont.)NF ORA-SS Schema Diagram (cont.) Some better solutions: Redundancies are removed, in normal form

staff#

ISBNtitle

titleauthor

professor

textbookstaff# name

course

C.Code

course textbook

+

C.Code titleISBN titleauthor

professor

textbookname

professor

course textbook

+

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Research Topics for ORA-SS ModelResearch Topics for ORA-SS Model Storage Schema for ORA-SS/XML DatabasesStorage Schema for ORA-SS/XML Databases

Main Rules– Each object class together with its attributes form a nested

relation (object relation)– Each relationship type together with its attribute form a

nested relation (relationship relation)

Nested relations can be handled by Object Relational model, e.g. ORACLE 8i.

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Research Topics for ORA-SS ModelResearch Topics for ORA-SS Model Storage Schema for ORA-SS/XML DatabasesStorage Schema for ORA-SS/XML Databases

Object Relations

Supplier (S#, Name, (City))

Part (P#, Name, color)

Project(J#, Name, Loc)

Relationship relations

SP (S#, P#, price)

SPJ (S#, P#, J#, Qty)

Constraint:

SPJ[S#, P#] SP[S#, P#]

PriceSP

SPJ3

Loc

City

NameJ#

SP2

Supplier

Project

Name

Part

Name

+

Color

Qty

SPJ

S#

P#

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Research Topics for ORA-SS ModelResearch Topics for ORA-SS Model ViewsViews What information can be directly derived from

references and class hierarchy

code

facultygradehistory

fs

grade

cs

fs,2,1:n,1:nfaculty

nametitle

cs,2,4:n,3:8

course

student

studentnumber

grade*

faculty

student

coursecode

number streetname

hostel home

|

Referencing an object class in an ORA-SS schema diagram

streetnumbername

cstitle

course

codestudent

grade |

hostel home

studentnumber

cs

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Research Topics for ORA-SS ModelResearch Topics for ORA-SS Model Views (cont.)Views (cont.) Valid views of an ORA-SS schema Operations: selection, projection, join, up/down

Qty Qty

total_qty

32

3price

2

Supplier

Project

Part

3

2

price

2

Part

Project

Supplier

3price

Project

Supplier

Part

Qty

Project

Part

223

3

2

2

View 2 View 3View 1

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Research Topics for ORA-SS ModelResearch Topics for ORA-SS Model Views (cont.)Views (cont.) Views from ORA-SS storage schema

Main Rules– The order of the object classes in a relationship relation can be

changed.– Object classes can be dropped from a relationship relation. In

this case, the attributes of the relationships will have different cardinalities or change to some aggregate functions such as sum, max/min, average, etc.

Other Topics on Views– materialized views and maintenance– view update problem

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Research Topics for ORA-SS ModelResearch Topics for ORA-SS Model Evaluating XML queries on ORA-SS DatabasesEvaluating XML queries on ORA-SS Databases

Map XML schema to ORA-SS schema– Extra information is needed

Map ORA-SS schema to storage schema (OR model) Map XML documents to ORA-SS databases

(using object relational model DBMS) Map XML queries to queries on the ORA-SS

databases– Need to handle recursions and wildcard such as *(any), |(or), !

(not), etc.

Result construction, i.e. to XML documents

Related issues:

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Research Topics for ORA-SS ModelResearch Topics for ORA-SS Model Translating Relational Schema into ORA-SS SchemaTranslating Relational Schema into ORA-SS Schema

Extra information needed:• FDs and keys

• Inclusion dependencies

• Semantic dependencies

Main steps:• Identify object classes and their attributes from object

relations

• Identify relationship classes and their attributes from relationship relations

• Identify class hierarchy

• Identify non key constraint functional dependencies

• Generate ORA-SS/XML Views for applications.

• Similar to translating relational schema to OO schema

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Applications of ORA-SSApplications of ORA-SS SummarySummary Introduced ORA-SS model Briefly discussed research topics using

ORA-SS Model– Normal form ORA-SS schema diagram– Storage schema for ORA-SS/XML databases– ORA-SS/XML views– Evaluating XML queries on ORA-SS databases– Translating relational schema into ORA-SS

schema