1.4 Patterns in XML

   

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In order to effectively model information using XML, we must learn how to identify the natural patterns inherent to it. First, we must determine whether we have used XML elements properly. To do this we will analyze the XML fragment shown in Listing 1.2.

Listing 1.2 Example XML Fragment

<colorimeter_reading>
      <device> X-Rite Digital Swatchbook </device>
      <patch> cyan </patch>
      <RGB resolution=8>
            <red> 0 </red>
            <green> 255 </green>
            <blue> 255 </blue>
      </RGB>
</colorimeter_reading>

We examine each data element and ask the following question:

• Is this data, or is it actually metadata (information about another data element)?

We examine every attribute and ask the following questions:

• Does the attribute tell us something about or describe how to interpret, use, or present data elements?

• Is the attribute truly metadata, and not actually a data element?

• Does it apply to all data elements in its scope?

We examine every tag and ask the following question:

• Does this tag help describe what all data elements in its scope are?

We examine the groupings we have created (the sibling relationships) and ask:

• Are all members of the group related in a way the parent nodes describe?

• Is the relationship between siblings unambiguous?

If the answer to any of the preceding questions is "no," then we need to cast the offending components differently.

After insuring that information has been expressed using the components of XML appropriately, we examine how everything has been stitched together. To do this we create an information context list from the XML fragment. This is done by simply taking each data element and writing down every tag and attribute leading up to it. The resulting lines will give us a flattened view of the information items contained in the XML fragment. A context list for the example XML fragment in Listing 1.2 would look like the one shown in Listing 1.3.

Listing 1.3 Context List for Example XML Fragment

<colorimeter_reading><device> X-Rite Digital Swatchbook
<colorimeter_reading><patch> cyan
<colorimeter_reading><RGB resolution=8><red> 0
<colorimeter_reading><RGB resolution=8><green> 255
<colorimeter_reading><RGB resolution=8><blue> 255

If we convert these lines to what they mean in English, we can see that each information item, and its context, makes sense and is contextually complete:

1. This colorimeter reading is from an X-Rite Digital Swatchbook.

2. This colorimeter reading is for a patch called cyan.

3. This colorimeter reading is RGB-red and has an 8-bit value of 0.

4. This colorimeter reading is RGB-green and has an 8-bit value of 255.

5. This colorimeter reading is RGB-blue and has an 8-bit value of 255.

Next we examine the groupings implied by the tag hierarchy:

• "<colorimeter_reading>" contains "<device>", "<patch>", and "<RGB>" (plus its children).

• "<RGB>" contains "<red>", "<green>", and "<blue>".

"<colorimeter_reading>" represents the root tag, so everything else is obviously related to it. The only other implied grouping falls under "<RGB>". These are the actual readings, and the only entries that are, so they are logically related in an unambiguous way.

Finally, we examine the scope for each attribute:

• "resolution=8" has the items "<red>", "<green>", and "<blue>" in its scope.

"resolution=8" logically applies to every item in its scope and none of the items not in its scope, so it has been appropriately applied.

A self-constructing XML information system (like NeoCore XMS) will use the structure of and the natural patterns contained in XML to automatically determine what to index. Simple queries are serviced by direct lookups. Complex queries are serviced by a combination of direct lookups, convergences against selected parent nodes, and targeted substring searches. With NeoCore XMS no database design or indexing instructions are necessary?the behavior of XMS is driven entirely by the structure of the XML documents posted to it. Index entries are determined by inference and are built based on the natural patterns contained in XML documents. NeoCore XMS creates index entries according to the following rules:

• An index entry is created for each data element.

• An index entry is created for each complete tag context for each data element?that is, the concatenation of every tag leading up to the data element.

• An index entry is created for the concatenation of the two preceding items (tag context plus data element).

For the XML fragment in Listing 1.2, the following items would be added to the pattern indices (actually, this list is not complete because partial tag context index entries are also created, but a discussion of those is beyond the scope of this chapter):

1. X-Rite Digital Swatchbook

2. cyan

3. 0

4. 255

5. 255

6. <colorimeter_reading><device>

7. <colorimeter_reading><patch>

8. <colorimeter_reading><RGB><red>

9. <colorimeter_reading><RGB><green>

10. <colorimeter_reading><RGB><blue>

11. <colorimeter_reading><RGB resolution=8>

12. <colorimeter_reading><device> X-Rite Digital Swatchbook

13. <colorimeter_reading><patch> cyan

14. <colorimeter_reading><RGB resolution=8><red> 0

15. <colorimeter_reading><RGB resolution=8><green> 255

16. <colorimeter_reading><RGB resolution=8><blue> 255

Entries 1?5 are data only, entries 6?11 are tag context only, and entries 12?16 are both.

At this point it is important to consider how performance will be affected by the structure of the XML document. Because the inherent patterns inferred from the XML itself can be used to automatically build a database, the degree to which those patterns match likely queries will have a big effect on performance, especially in data-centric applications where single data elements or subdocuments need to be accessed without having to process an entire XML document.

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Top Title TOC Preface P.1 What Is XML? P.2 XML Concepts P.3 XML-Related Technologies P.4 XML Data Management P.5 How This Book Is Organized P.6 Who Should Read This Book P.7 Resources Acknowledgments Chapter 8 Chapter 12 Chapter 13 Chapter 14 Chapter 19 Part I: What Is XML? Chapter 1. Information Modeling with XML 1.1 Introduction 1.2 XML as an Information Domain 1.3 How XML Expresses Information 1.4 Patterns in XML 1.5 Common XML Information-Modeling Pitfalls 1.6 A Very Simple Way to Design XML 1.7 Conclusion Part II: Native XML Databases Chapter 2. Tamino-Software AG's Native XML Server 2.1 Introduction 2.2 Tamino Architecture and APIs 2.3 XML Storage 2.4 Querying XML 2.5 Tools 2.6 Full Database Functionality 2.7 Conclusion Chapter 3. eXist Native XML Database 3.1 Introduction 3.2 Features 3.3 System Architecture Overview 3.4 Getting Started 3.5 Query Language Extensions 3.6 Application Development 3.7 Technical Background 3.8 Conclusion Chapter 4. Embedded XML Databases 4.1 Introduction 4.2 A Primer on Embedded Databases 4.3 Embedded XML Databases 4.4 Building Applications for Embedded XML Databases 4.5 Conclusion Part III: XML and Relational Databases Chapter 5. IBM XML-Enabled Data Management Product Architecture & Technology 5.1 Introduction 5.2 Product and Technology Offering Summaries 5.3 Current Architecture and Technology 5.4 Future Architecture and Technology 5.5 Conclusion Notices Chapter 6. Supporting XML in Oracle9i 6.1 Introduction 6.2 Storing XML as CLOB 6.3 XMLType 6.4 Using XSU for Fine-Grained Storage 6.5 Building XML Documents from Relational Data 6.6 Web Access to the Database 6.7 Special Oracle Features 6.8 Conclusion Chapter 7. XML Support in Microsoft SQL Server 2000 7.1 Introduction 7.2 XML and Relational Data 7.3 XML Access to SQL Server 7.4 Serializing SQL Query Results into XML 7.5 Providing Relational Views over XML 7.6 SQLXML Templates 7.7 Providing XML Views over Relational Data 7.8 Conclusion Chapter 8. A Generic Architecture for Storing XML Documents in a Relational Database 8.1 Introduction 8.2 System Architecture 8.3 The Data Model 8.4 Creating the Database 8.5 Connecting to the Repository 8.6 Uploading XML Documents 8.7 Querying the Repository 8.8 Further Enhancements 8.9 Conclusion Chapter 9. An Object-Relational Approach to Building a High-Performance XML Repository 9.1 Introduction 9.2 Overview of XML Use-Case Scenario 9.3 High-Level System Architecture 9.4 Detailed Design Descriptions 9.5 Conclusion Part IV: Applications of XML Chapter 10. Knowledge Management in Bioinformatics 10.1 Introduction 10.2 A Brief Molecular Biology Background 10.3 Life Sciences Are Turning to XML to Model Their Information 10.4 A Genetic Information Model 10.5 NeoCore XMS* 10.6 Integration of BLAST into NeoCore XMS Conclusion Chapter 11. Case Studies of XML Used with IBM DB2 Universal Database 11.1 Introduction 11.2 Case Study 1: "Our Most Valued Customers Come First" 11.3 Case Study 2: "Improve Cash Flow" 11.4 Conclusion Notices Chapter 12. The Design and Implementation of an Engineering Data Management System Using XML and J2EE 12.1 Introduction 12.2 Background and Requirements 12.3 Overview 12.4 Design Choices 12.5 Future Directions 12.6 Conclusion Chapter 13. Geographical Data Interchange Using XML-Enabled Technology within the GIDB System 13.1 Introduction 13.2 GIDB METOC Data Integration 13.3 GIDB Web Map Service Implementation 13.4 GIDB GML Import and Export 13.5 Conclusion Chapter 14. Space Wide Web by Adapters in Distributed Systems Configuration from Reusable Components 14.1 Introduction 14.2 Advanced Concept Description: The Research Problem 14.3 Integration of Components with Architecture 14.4 Example 14.5 Future Generation NASA Institute for Advanced Concepts, Space Wide Web Research, and Boundaries 14.6 Advanced Concept Development 14.7 Conclusion Chapter 15. XML as a Unifying Framework for Inductive Databases 15.1 Introduction 15.2 Past Work 15.3 The Proposed Data Model: XDM 15.4 Benefits of XDM 15.5 Toward Flexible and Open Systems 15.6 Related Work 15.7 Conclusion Chapter 16. Designing and Managing an XML Warehouse 16.1 Introduction 16.2 Architecture 16.3 Data Warehouse Specification 16.4 Managing the Metadata 16.5 Storage and Management of the Data Warehouse 16.6 DAWAX: A Graphic Tool for the Specification and Management of a Data Warehouse 16.7 Related Work 16.8 Conclusion Part V: Performance and Benchmarks Chapter 17. XML Management System Benchmarks 17.1 Introduction 17.2 Benchmark Specification 17.3 Benchmark Data Set 17.4 Existing Benchmarks for XML 17.5 Conclusion Chapter 18. The Michigan Benchmark: A Micro-Benchmark for XML Query Performance Diagnostics 18.1 Introduction 18.2 Related Work 18.3 Benchmark Data Set 18.4 Benchmark Queries 18.5 Using the Benchmark 18.6 Conclusion Chapter 19. A Comparison of Database Approaches for Storing XML Documents 19.1 Introduction 19.2 Data Models for XML Documents 19.3 Databases for Storing XML Documents 19.4 Benchmarking Specification 19.5 Test Results 19.6 Related Work 19.7 Summary Chapter 20. Performance Analysis between an XML-Enabled Database and a Native XML Database 20.1 Introduction 20.2 Related Work 20.3 Methodology 20.4 Database Design 20.5 Discussion 20.6 Experiment Result 20.7 Conclusion Chapter 21. Conclusion References Contributors Editors Chapter 1: Information Modeling with XML Chapter 2: Tamino-Software AG's Native XML Server Chapter 3: eXist Native XML Database Chapter 4: Embedded XML Databases Chapter 5: IBM XML-Enabled Data Management Product Architecture and Technology Chapter 6: Supporting XML in Oracle9i Chapter 7: XML Support in Microsoft SQL Server 2000 Chapter 8: A Generic Architecture for Storing XML Documents in a Relational Database Chapter 9: An Object-Relational Approach to Building a High-Performance XML Repository Chapter 10: Knowledge Management in Bioinformatics Chapter 11: Case Studies of XML Used with IBM DB2 Universal Database Chapter 12: The Design and Implementation of an Engineering Data Management System Using XML and J2EE Chapter 13: Geographical Data Interchange Using XML-Enabled Technology within the GIDB System Chapter 14: Space Wide Web by Adapters in Distributed Systems Configuration from Reusable Components Chapter 15: XML as a Unifying Framework for Inductive Databases Chapter 16: Designing and Managing an XML Warehouse Chapter 17: XML Management System Benchmarks Chapter 18: The Michigan Benchmark: A Micro-Benchmark for XML Query Performance Diagnostics Chapter 19: A Comparison of Database Approaches for Storing XML Documents Chapter 20: Performance Analysis between an XML-Enabled Database and a Native XML Database Remember the name: eTutorials.org Copyright eTutorials.org 2008-2023. 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