A Layered View Model for XML with Conceptual and Logical Extensions, and its Applications Submitted by Rajugan Rajagopalapillai A thesis submitted in total fulfillment of the requirements for the degree of Doctor of Philosophy Faculty of Information Technology University of Technology, Sydney (UTS) Sydney, NSW 2007 Australia February 2006
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A Layered View Model for XML
with Conceptual and Logical Extensions,
and its Applications
Submitted by
Rajugan Rajagopalapillai
A thesis submitted in total fulfillment
of the requirements for the degree of
Doctor of Philosophy
Faculty of Information Technology
University of Technology, Sydney (UTS)
Sydney, NSW 2007
Australia
February 2006
CERTIFICATE OF AUTHORSHIP/ORIGINALITY
I certify that the work in this thesis has not previously been submitted for a
degree nor has it been submitted as part of requirements for a degree except as
fully acknowledged within the text.
I also certify that the thesis has been written by me. Any help that I have
received in my research work and the preparation of the thesis itself has been
acknowledged. In addition, I certify that all information sources and literature
used are indicated in the thesis.
Date:/£ leyl>oob
n
Acknowledgements
I am greatly indebted to my supervisors Professor Tharam Dillon, Professor Elizabeth
Chang and Associate Professor Ling Feng for their encouragement and advice, and for
providing constant direction and focus to my research. I owe my research
achievements to their experienced supervision and unconstraint support.
I thank Professor Tharam S. Dillon for his step-by-step guidance, many hours
of research discussions, suggestions, comments and kindhearted support during
difficult times. I owe a big thank you to Professor Elizabeth Chang for her many years
of unconstraint encouragement and support, patient discussions, motivating comments
and advice. 1 thank Associated Professor Ling Feng for her invaluable suggestions,
research discussions and comments on my research ideas and concepts. I am a much
better researcher because of my supervisors’ excellent guidance.
My thanks also go out to Associate Professor Wenny Rahayu for her help
during my research years. I owe special round of thanks to my friends and colleagues
at the Faculty of IT, UTS and at the Department of CS-CE, Latrobe University. I also
thank Bruna Pomella for commenting ambiguous sentences and correcting
grammatical mistakes.
Finally, I owe my success in life to the hard work and sacrifices of the two
most important people in my life; Amma and Appa, my parents. 1 thank them for their
unconstraint support and giving me the strength for letting my dream to come true.
Table of Contents
Certificate of Authorship / Originality ii
Acknowledgments iii
Contents iv
List of Figures X
List of Tables xii
Abstract xiii
List of Publications XV
1 GENERAL CONSIDERATIONS AND MOTIVATION............................................. 1
1.1 Introduction................................................................................................................ 11.2 Data Models...............................................................................................................2
1.2.1 Data Models and Schema........................................................................................ 31.2.2 The “Web” Data Model.......................................................................................... 41.2.3 The Semi-Structured Data Model & XML............................................................ 4
1.3 Data Modelling & Challenges............................................................................... 61.4 The View.................................................................................................................... 10
1.4.1 View Properties......................................................................................................101.4.2 Views and Data Models......................................................................................... 12
1.5 Motivation................................................................................................................151.6 Aim & Scope of Thesis............................................................................................... 191.7 Plan of the Thesis..................................................................................................... 21References..............................................................................................................................25
2 EVALUATION OF THE EXISTING LITERATURE ON VIEWS....................... 33
2.1 Introduction............................................................................................................. 332.2 The Notion of Views............................................................................................... 342.3 Views for Relational Model............................................................................... 352.4 Views for Object-Oriented Paradigm................................................................402.5 Views for Semi-Structtjred Data.......................................................................44
2.5.1 Declarative XML Views.........................................................................................462.5.2 View Mechanism in Xyleme...................................................................................472.5.3 Views in the ORA-SS Model..................................................................................482.5.4 Technology Specific View Formalisms.................................................................50
2.5.4.1 Active XML Views......................................................................................... 512.5.4.2 Views in the MIX System................................................................................51
2.6 The Semantic Web Paradigm and Views.............................................................52
2.6.1 RDF Views..............................................................................................................542.6.2 OWL Views.............................................................................................................562.6.3 Ontology Views in the MOVE System...................................................................57
2.7 Issues Associated with View Formalisms......................................................... 572.7.1 Alternative View Concepts.................................................................................... 582.7.2 Conceptual Semantics for Views........................................................................... 592.7.3 View Constraints..................................................................................................... 602.7.4 Remarks..................................................................................................................61
3.4 Extensible Markup Language (XML)................................................................ 893.4.1 Document Type Definition (DTD)..........................................................................923.4.2 XML Schema.......................................................................................................... 923.4.3 XML Schema Components.................................................................................... 943.4.4 Other Schemas for XML....................................................................................... 953.4.5 Schema Document and Instance Document...........................................................963.4.6 Namespaces......................................................................................................... 100
3.5 Documents, Schema, Operators & Query Expressions.................................1013.5.1 Root Node............................................................................................................ 1023.5.2 Edges....................................................................................................................1023.5.3 An XML Document..............................................................................................1043.5.4 An XML Schema Document................................................................................ 1053.5.5 Path......................................................................................................................1063.5.6 Operators............................................................................................................... 1093.5.7 Query Expression................................................................................................109
3.6 Views........................................................................................................................1103.7 Views for XML...................................................................................................... Ill
3.7.1 XML Document Structure and XML Views..........................................................1133.7.2 Data Model, Query and XML Views................................................................. 1143. 7.3 Applications and Integration of XML Views........................................................1183. 7.4 Properties of an Ideal View Mechanism for XML.............................................118
3.8 The Problem Definition...................................................................................... 1203.9 Evaluation of Feasible Solutions....................................................................1223.10 Conclusion............................................................................................................. 122References............................................................................................................................ 123
4 OVERVIEW OF THE SOLUTION...........................................................................130
4.1 Introduction......................................................................................................... 1304.2 An illustrative Case-Study Examples........................................................... 130
4.2.1 Illustrative Case-Study Example -1..................................................................... 131
V
4.2.2 An illustrative Case-Study Example - II.............................................................. 1324.3 Solution Outline...................................................................................................1354.4 Views for XML....................................................................................................... 138
4.4.1 Imaginary Document Terminology......................................................................1384.4.2 Imaginary XML Document.................................................................................. 140
4.11 The Framework: A Layered View Model for XML....................................... 1604.11.1 Modelling Conceptual Views in the Layered View Model (LVM)............... 161
4.11.1.1 The XSemantic Nets.................................................................................... 1634.11.1.2 OMG’s UML/OCL........................................................................................ 165
4.11.2 Specifying Conceptual View Constraints in the LVM................................... 1674.11.3 View Transformation Methodology in the LVM............................................169
5.3.4 Some Examples of the Conceptual Operators................................................... 2095.4 Modeling Conceptual Views............................................................................. 2105.5 Constraint Specification in Conceptual Views............................................2115.6 Conclusion............................................................................................................. 219References.......................................................................................................................... 219
6 MODELLING AND TRANSFORMATION I.........................................................222
6.4.2 Conceptual View Constraints........................................................................... 2386.4.2.1 Constraints Defined over an Edge................................................................... 2396.4.2.2 Constraints Defined over a Set of Edges.......................................................... 2426.4.2.3 Constraints Defined over a Node..................................................................... 244
6.5 Schemata Transformation of Conceptual Views to Logical Views......2486.5.1 Schemata Transformation of Nodes.................................................................. 249
6.5.1.1 Transformation of Basic Nodes.......................................................................2496.5.1.2 Transformation of Complex Nodes................................................................. 2506.5.1.3 Transformation of Semantic Relationships.......................................................2516.5.1.4 Conceptual Views.......................................................................................... 260
6.5.2 Schemata Transformation of Conceptual View Constraints............................2616.5.2.1 Uniqueness Constraint....................................................................................2626.5.2.2 OID Constraint...............................................................................................2626.5.2.3 Referential Constraints................................................................................... 2646.5.2.4 Ordered Composition.....................................................................................2656.5.2.5 Exclusive Disjunction.....................................................................................2666.5.2.6 Constructional Constraints..............................................................................267
6.6 Conceptual View Dynamic Properties............................................................ 2686.7 Declarative Transformation of Dynamic Properties into Document View'Expressions.......................................................................................................................... 270
6.7.1 Choice of Document View Query Languages....................................................2716.7.1.1 XPath............................................................................................................2716.7.1.2 XSI.T............................................................................................................ 2716.7.1.3 Non-query procedural language (e.g. Java, C++, etc.)...................................... 2726.7.1.4 XQuery......................................................................................................... 273
6.7.2 Transformation of Conceptual Operators to Document View Expressions 2746.7.2.1 Transformation of Conceptual Binary Operators to XQuery.............................2776.7.2.2 Transformation of Conceptual Unary Operators to XQuery............................. 279
6.7.3 Document Manipulation and Weak Encapsulation in the LVM Views.............2826.7.4 Example Transformation of Conceptual Operators to Document Views in the e-Sol 287
7 MODELLING AND TRANSFORMATION II.......................................................295
7.1 Introduction.........................................................................................................2957.2 Modelling with UML/OCL.................................................................................2967.3 Modelling with Conceptual Views using UML/OCL................................... 298
8 CASE STUDY & APPLICATIONS I: VIEW-DRIVEN XML DOCUMENTWAREHOUSE MODEL..........................................................................................................324
8.1 Introduction.........................................................................................................3248.2 Motivation.............................................................................................................3258.3 Data Warehouses................................................................................................ 327
8.4 Background........................................................................................................... 3308.5 Example Case Study.............................................................................................3328.6 The XML Document Warehouse Model (XDW).............................................. 333
8.6.1 XDW Conceptual Level...................................................................................... 3368.6.1.1 The XML FACT Repository............................................................................3378.6.1.2 View-Driven xFACT...................................................................................... 3388.6.1.3 Virtual Dimensions......................................................................................... 338
8.7 XDW Model Semantics....................................................................................... 3398.7.1 xFACT and View-Driven VDim..........................................................................3398.7.2 XDW Relationships...............................................................................................341
8.8 XDW Modelling and Transformation............................................................ 3428.9 View-Driven XML FACT Repository............................................................... 345
8.9.1 PIM: (fxFACTProperties................................................................................... 3468.9.2 Formal Semantic of (fxFA CT.............................................................................. 3488.9.3 Design Steps in Modelling gxFACT...................................................................3528.9.4 PSM: Implementation Choices for the QxFACT................................................ 354
9 CASE STUDY & APPLICATIONS II: VIEWS FOR SEMANTIC WEB, VIEW-DRIVEN ONTOLOGY EXTRACTION................................................................................362
9.1 Introduction..........................................................................................................3629.2 The Semantic Web.................................................................................................363
9.3 Background........................................................................................................... 3679.4 Motivation............................................................................................................. 3699.5 Case Study Example.............................................................................................3719.6 Views for Semantic Web..................................................................................... 372
9.7 Transformation Ontology View to the Materialized Ontology ViewExtractor (MOVE) System...............................................................................................3869.8 Conclusion............................................................................................................. 388References............................................................................................................................388
10 CASE STUDY & APPLICATIONS III: VIEW-DRIVEN WEBSITE & WEBPORTAL DESIGN.................................................................................................................... 394
10.1 Introduction..........................................................................................................39410.2 Web Engineering...................................................................................................39510.3 Motivation............................................................................................................. 39910.4 Background...........................................................................................................40010.5 Example Case Study............................................................................................ 40410.6 Extensible Web (xWeb)...................................................................................... 406
10.7 xWeb and xPortal Semantics............................................................................ 41010.7.1 xWeb Semantics..............................................................................................41010.7.2 xPortal Semantics...........................................................................................414
10.8 A Practical Walkthrough of the xWeb Design Methodology............... 41710.9 Conclusion.............................................................................................................429References........................................................................................................................... 429
11 RECAPITULATION, FUTURE WORK AND CONCLUSION.......................... 435
11.2 Recapitulation.......................................................................................................43511.3 Future Work Introduction.................................................................................440
11.3.1 Future Research Issues in the LVM for XML.............................................. 44011.3.2 Future Research in the Semantic Web Paradigm and its Applications 442
APPENDIX A SELECTED PUBLICATIONS.....................................................................448
List of Figures
Figure 1.1: Data modelling methodologies.......................................................................... 7Figure 1.2: Grouping of chapters...........................................................................................21Figure 1.3: Plan of chapters and their inter-relationships............................................23Figure 3.1: XSemantic net notations.....................................................................................86Figure 3.2: XSemantic net examples......................................................................................87Figure 3.3: Graphical representation of class, attributes, methods and visibility in
UML...................................................................................................................................... 88Figure 3.4: Graphical representation of 00 relationships in UML............................. 89Figure 3.5: an XML document - books.xmi........................................................................... 90Figure 3.6: A simple DTD - book.dtd...................................................................................... 92Figure 3.7: A simple XML Schema - book.xsd.......................................................................93Figure 3.8: A W3C XML Schema example...........................................................................100Figure 3.9: Views in traditional data engineering approach...................................... 115Figure 4. l: CPS simplified model (UML)............................................................................. 132Figure 4.2: CPS simplified model (XSemantic nets)......................................................... 133Figure 4.3: e-Sol context diagram (simplified).................................................................. 134Figure 4.4: A simplified e-Sol use-case diagram................................................................135Figure 4.5: Conceptual operators vs. XML query expressions (context diagram) .15!Figure 4.6: An overview of the Layered View Model (LVM)........................................ 160Figure 4.7: The Layered View Model (design steps)..........................................................162Figure 4.8: Transformation methodologies in the LVM................................................. 169Figure 4.9: Applications and utilization of the LVM and real-world scenarios.... 171Figure 5.1: Layered View Model for XML (context diagram).......................................181Figure 5.2: Transformation of conceptual views to logical views............................ 188Figure 5.3: Transformation of conceptual operators to document views................ 191Figure 5.4: CPS and examples of contexts (UML representation)................................195Figure 5.5: CPS and examples of contexts (XSemantic net representation).............196Figure 6.1: XSemantic net Notation.................................................................................... 235Figure 6.2: A conceptual view example in the e-Sol (“Income”)................................... 236Figure 6.3: Conceptual view semantic relationship examples (aggregation, of-
Manager)......................................................................................................................... 301Figure 7.6: A conceptual view example in the e-Sol (“Income”).................................. 302Figure 7.7: Conceptual view semantic relationship examples in the e-Sol...............303Figure 7.8: Aggregation relationships examples............................................................ 305Figure 7.9: A conceptual view package notation and an example (WMS-Users
PACKAGE)........................................................................................................................... 306Figure 7.10: Homogenous composition example................................................................ 308Figure 7.11: Ordered-Composition....................................................................................... 308Figure 7.12: Adhesion constraint........................................................................................ 309Figure 7.13: Ordered and adhesion constraint examples in e-Sol............................... 309Figure 7.14: Exclusd'e disjunction.......................................................................................310Figure 7.15: e-Sol domain objects and conceptual views (WMS)................................. 312Figure 7.16: Constructional constraints..........................................................................313Figure 8. l: XDW Model (context diagram).......................................................................334Figure 8.2: A VDim hierarchy in e-Sol-W case study (with UML stereotypes)........ 343Figure 8.3: AnxFACT example in the e-Sol-W (WMS-Warehouse)..............................345Figure 8.4: £XFACT context diagram.................................................................................348Figure 8.5: xFACTs and the view contexts (^xFACT).......................................................349Figure 9. l: A simple ontology in the e-Sol (UML)............................................................ 372Figure 9.2: A simple ontology example in f.-Sol............................................................... 373Figure 9.3: LVM for Semantic Web (ontology views)...................................................... 377Figure 9.4: Ontology conceptual view / sub-ontology example in e-Sol...................383Figure 9.5: Ontology conceptual view / sub-ontology examples in e-Soi.................. 384Figure 10.1: eXel web user hierarchy (UML)................................................................... 405Figure 10.2: xWeb context diagram.....................................................................................406Figure 10.3: xWeb/xPortal conceptual level dependencies (context diagram).....418Figure 10.4: Use-case analysis of the example case study (visitor, member).......... 419Figure 10.5: Use-case analysis of the case study (administrator, collaborative
PARTNER)...........................................................................................................................420Figure 10.6: Web repository model (conceptual level).................................................421Figure 10.7: View repository model (conceptual level).................................................422Figure 10.8: Portal repository model (conceptual level)............................................ 423Figure 10.9: Web repository logical model (graphical representation of the
resulted XML Schema)................................................................................................. 424Figure 10.10: View repository logical model (graphical representation of the
resulted XML Schema)................................................................................................. 424Figure 10.11: xWeb page example (http://exel.it.uts.edu.au/index.html)................... 426Figure 10.12: xWeb page example - member list (http://exel.it.uts.edu.au/people.php)
........................................................................................................................................... 426Figure 10.13: aWeb page example - publications
(http://exel.it.uts.edu.au/publications.php)............................................................426Figure 10.14: xPortal example - member profile (under development).......................429
List of Tables
Table 3.1: Different Terminologies for Different Paradigms.......................................96Table 3.2: Different Terminologies for Different Paradigms.......................................99Table 4.1: View Terminology for Different Paradigms................................................. 138Table 4.2: View Terminology/Representation for the Different Paradigms.......... 140Table 4.3: Imaginary XML Document Terminology and Representations at
Different Abstraction Levels..................................................................................... 142Table 6.1: Relationships and cardinality constraints.................................................. 239Table 6.2: Summary of the transformation between conceptual level and
document level concepts............................................................................................. 276Table 6.3 Summary of the transformation of conceptual operators to document
views (XQuery)................................................................................................................283Table 6.4: Summary of the generic operations permitted in the LVM........................286Table 6.5: Summary of the transformation of LVM generic methods to document
view expressions (XQuery)...........................................................................................287Table 7.1: Summary of conceptual views (UML/OCL) to logical views (XML Schema)