1. A Unified Framework for the Semantic Integration of XML Databases
First  IEEE International Conference on Digital Information Management (ICDIM)
A Unified Framework for the Semantic Integration of XML Databases
Doan Dai Duong and Le Thi Thu Thuy
{Duong_Dai.Doan, The University of New Brunswick, Fredericton, NB, Canada
Presented by
Virendrakumar C. Bhavsar
December 06-08, 2006

2. Agenda Introduction XML Declarative Description (XDD)
Modeling of Data Components
Modelling of Processing Components
Conclusion

3. Introduction General model of XML database integration
Step 1: Schema Integration
convert
RDS
OODS
Integrated XML schema
Set of mappings
XML Database Schema
Integration System
XML schema1
XML schemaN
XML schema2
Ontology

4. Step 2: Query Processing
Integrated data
<studenewrrwerr">
<Fname>>
<room/rrrrrrrrrrr>
<national/rrewe>
</studeerewrewnt> s n r c
xxx xx x
Integrated schema
Users
query
<Fname>>
<national/>
</student>
<student source=“A">
<Fname> Xuan</Fname>
<room>G26</room>
<nationality>Vietnam</nationality>
</student>
<student source="B">
<Fname>Phuoc</Fname>
<room>A12</room>
<nationality>Campuchia</nationality>
Local data
<student source="B">
<Fname> Xuan</Fname>
<room>G26</room>
<nationality>Vietnam</nationality>
</student>
<Fname>Phuoc</Fname>
<room>A12</room>
<nationality>Campuchia</nationality>
Local data
<student source=“C">
<Fname> Xuan</Fname>
<room>G26</room>
<nationality>Vietnam</nationality>
</student>
<student source="B">
<Fname>Phuoc</Fname>
<room>A12</room>
<nationality>Campuchia</nationality>
Local data 4

5. XDD as underlying model
Proposed Integration Framework
XDD as underlying model
XMLSchema
XML database
XML data
XML query
Integration
system
Integrated schema
Database sources
Metadata
User query
Integrated data
Powerful
XDD supports for all tasks of framework
Input XML query, input XML data, output XML data
Rules, constraints, mappings
Metadata
Based on XML standard format, XDD combines all tasks of framework tightly and makes it easily to manipulate data
Reduce time and effort of programmers and users and syntax errors
vbnbmnbm 5

6. XML Declarative Description*
XML Declarative Description (XDD) is XML-based information representation
Ordinary XML expressions (ground XML expressions)+ variables = Non-ground XML expressions
 Enhancement of expressive power and representation of implicit information
XML clauses of the form
H ← B1, … , Bm, C1, …, Cn
 Able to express conditions, constraints
*Wuwongse, V., Anutariya, C., Akama, K., and Nantajeewarawat, E. XML Declarative Description (XDD): A Language for the Semantic Web. IEEE Intelligent Systems, Vol. 16, No. 3, (2001) 54-65

7. Modeling of Data Components
XML Databases
Extension (actual data values): ground XML expressions
Intension (schemas, logical specifications, relationships, indexes and constraints): non-ground XML expressions
XML Queries
Include constructor, patterns, and filters
Correspond to three parts (H, Bi, Cj) of XDD rule
H  B1 …, Bm, C1,…,Cn

8. Modeling of Data Components
constructor
pattern
filter
Query modelled by XDD

9. Data source Query Query Execution Example result1 result2
<Student>
<name>John</name>
<nationality>Canadian
</nationality>
<GPA>4</GPA>
</Student>
<name>Duong</name>
<nationality>Vietnamese
<GPA>4.2</GPA>
<phone> <phone>
<ID> <ID>
<phone> <phone>
Data source
Query
result1
result2

10. Modeling of Data Components
Mappings
Describes correspondence between object in integrated schema and its corresponding objects in local schemas
Supports decomposing XML queries and converting data
Modeled by non-ground XML expressions

11. Sample of Mappings Object in integrated schema Object in schema A
Object in schema B

12. Modelling of Processing Components
Schema Integration Component
The main task is to resolve conflicts between schemas of participating databases
Conflict resolution between various schemas is done at one time (one-shot strategy)
Each local schema is big non-ground XML expression ($E_variable)

13. Schema Integration Component
XDD can interactively process all schemas as $E expressions
<Integrating_schema>
<schema name="1">…</schema>
<schema name="2">…</schema> …
<schema name="n">…</schema>
</Integrating_schema>
<schema name="1">
</schema>
<schema name="2">
<schema name="n">
$E expression

14. Schema Conflict Classification
Conflicts between schemas can be classified into four main kinds
Naming conflicts
Synonyms
Acronyms
Homonyms
Structural conflicts
Missing items conflicts
Internal path discrepancy conflicts
Aggregation conflicts
Generalization/specification
Constraint conflicts
Occurring numbers of elements
Fixed vs. default values
Constraints of attributes
Data type conflicts
Disjoint or incompatible data types
Compatible data types
IDREF and IDREFS

15. New data type is created
Aggregation
conflict
Professor
FName
MName
LName
Name
Union rule
Aggregation checking and
data type constructing rule
New data type is created 14

16. Query Decomposition
The main task  yield n local subqueries from global query
<student id =“$S:id”>
<name>$S:name</name>
<country>$S:country</country>
</student>
student
country
field
name
position id
Integrated schema
SATstudent
country
fieldStudy
fullname
key
<SATstudent key =”$S:id” source=”B”>
<fullname> $S:name </fullname>
<country>$S:country</country>
</SATstudent>
Schema for source B
SOMstudent
nation
program
name
position id
<SOMstudent id=”$S:id” source=”A”>
<name> $S:name </name>
<nation>$S:country</nation>
</SOMstudent>
Schema for source A

17. Mappings from global to local
Query Decomposition
Mappings from global to local
A. Brief view
Sub query for local source
query
Query Decomposition
Sub query for local source
B. Solution
Input XML query
<student id =”$S:id”>
<name>$S:name</name>
<country>$S:country</country>
</student>
XML metadata
XDD rules for
transformation
<name> $S:name</name>
<fullname> $S:name </fullname>
<SATstudent key =”$S:id” source=”B”>
<country>$S:country</country>
</SATstudent>
<SOMstudent id =”$S:id” source=”A”>
<nation>$S:country</ nation>
</SOMstudent>
Output XML queries 16

18. Query Decomposition Example
<answer>
<SATstudent source=”B”>
<country>$S:country</country>
</SATstudent>
<SOMstudent source=”A”>
<nation>$S:country</nation>
</SOMstudent>
</answer>
Local query for source A 4
results in
Local query for source B
<answer>
$E:expression
</answer> 
<Mapping>
<student>
<country>$S:country</country>
</student>
<local>$E:expression</local>
</Mapping> 3
infers to
matches with 1
<Mapping>
<student>
<country>$S:country</country>
</student>
<local>
<SATstudent source=“B">
</SATstudent>
<SOMstudent source=“A">
<nation>$S:country</nation>
</SOMstudent>
</local>
</Mapping>
bounds to 2

19. Query Decomposition
Using special structure of mapping and applying XDD rules for query decomposition
Subqueries for distributed data sources are simultaneously produced
Similarly for data conversion, extracted data are simultaneously converted to global schema format

20. Conclusion
XDD is used to model all data components and processing components of XML database integration framework
Components of system modeled by XDD can communicate and exchange data easily
Special structure for XDD-based bidirectional mappings is designed. Information is produced efficiently for both query decomposition and data conversion, avoiding data redundancy
The framework can
Integrate n participating schemas
Decompose a query into n subqueries at a time.

21. Thank you !