1. 數位圖書館 – XML 系統應用 Jian-hua Yeh ( 葉建華 ) 真理大學資訊科學系助理教授 au4290@email.au.edu.tw

2. 2 Outline XML language introduction XML server architecture XML query language design issues

3. 3 XML Introduction What is XML? Why XML? The XML power XML and the enterprise

4. 4 What is XML? Proposed by W3C at the end of 1996 SGML-derived A meta-language for new tagging language XML1.0 Recommendation released at Feb. 1998 Supporting –Sun, Microsoft, Netscape, Adobe, ArborText, etc.

5. 5 What is XML? (2) eXtensible Markup Language Tag-based Open and cross-platform Structural data representation As data and as document Suitable for data exchange

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7. 7 Why XML? HTML is not enough, no structural data handling capability Recommended by W3C, an open standard The push of enterprise integration To break the stovepipe system, from vertical to horizontal The need of B2B, B2C integration Platform independent

8. 8 Traditional Data Exchange Handling Private protocol for stovepipe system Open standard for data exchange –RPC –RMI –CORBA –COM

9. 9 New Strategy of Data Exchange Text-based Tag-oriented Self-descriptive Data Type Definition

10. 10 XML Details Components –DTD –XML content Processing models –Event driven model: SAX A document is treated as a set of events –Structural model: DOM A document is represented as a tree structure

11. 11 XML Server Introduction Why XML server? –Comply with enterprise service model: client/middle/EIS structure Common components can consists of 3 rd party software vendors –XML parser, XSL processor, etc.

12. 12 XML Server Architecture

13. 13 XML Server Architecture (2) Key aspects –Client PDA, browser, Web server, other XML server, etc. –Communication protocol Email, HTTP, FTP, EJB, RMI, IIOP, COM, etc. –Key services –Data object Relational database, object data source, etc.

14. 14 XML Server Components Client Communication service Document handler Data object access module XML core service

15. 15 An Operation Example

16. 16 XML support in Java technology XML processing Data binding Remote communication Service registry Messaging

17. 17 Java for XML Processing JAXP (Java API for XML Processing) –SAX (Simple API for XML) parser Event-based XML parsing –DOM (Document Object Model) parser Model-based XML parsing –XSLT (XML Stylesheet Language for Transformations) processor Support SAX, DOM, stream-specific processing

18. 18 Java for XML Data Binding JAXB (Java Architecture for XML Binding) –Schema-based –Validation –Representing XML content

19. 19 Java for XML Communication JAX-RPC (Java API for XML-based RPC) –RPC-based Web service –SOAP-based (Simple Object Access Protocol) –Discoverable by using JAXR (*later*)

20. 20 Java for XML Registries JAXR (Java API for XML Registries) –Service registration –Service lookup

21. 21 Java for XML Messaging JAXM (Java API for XML Messaging) –Message provider SAAJ (SOAP with Attachments API for Java) –Message population with attachment

22. 22 XML Processing, How? Locating: XPath Querying: XQL, XQuery Storage: XMLDB

23. 23 What is XPath? W3C standard A syntax for defining parts of an XML document Uses paths to define XML elements Defines a library of standard functions A major element in XSLT

24. 24 Sample XML Empire Burlesque Bob Dylan 10.90 Hide your heart Bonnie Tyler 9.90 Greatest Hits Dolly Parton 9.90 Path –/catalog/cd/price Function –/catalog/cd[price>10.80]

25. 25 XPath: The Syntax

26. 26 Path Syntax: Locating Nodes /catalog/cd/price //cd /catalog/cd/* /catalog/*/price /*/*/price //* Empire Burlesque Bob Dylan 10.90 Hide your heart Bonnie Tyler 9.90 Greatest Hits Dolly Parton 9.90

27. 27 Path Syntax: Selecting Branches /catalog/cd[1] /catalog/cd[last()] /catalog/cd[price] /catalog/cd[price=10.90] /catalog/cd[price=10.90]/p rice Empire Burlesque Bob Dylan 10.90 Hide your heart Bonnie Tyler 9.90 Greatest Hits Dolly Parton 9.90

28. 28 Path Syntax: Selecting Several Paths /catalog/cd/title | /catalog/cd/artist //title | //artist //title | //artist | //price Empire Burlesque Bob Dylan 10.90 Hide your heart Bonnie Tyler 9.90 Greatest Hits Dolly Parton 9.90

29. 29 Path Syntax: Selecting Attributes //@country //cd[@country] //cd[@*] //cd[@country='UK'] Empire Burlesque Bob Dylan 10.90 Hide your heart Bonnie Tyler 9.90 Greatest Hits Dolly Parton 9.90

30. 30 XPath: Location paths

31. 31 Formal Syntax axisname::nodetest[predicate] –child::price[price=9.90]

32. 32 Axes and Node Tests

33. 33 Abbreviated Syntax

34. 34 Location Paths Examples

35. 35 XPath: The expressions

36. 36 Expression Types Numerical expressions Equality expressions Relational expressions Boolean expressions

37. 37 Numerical Expressions

38. 38 Equality Expressions

39. 39 Relational Expressions

40. 40 Boolean Expressions

41. 41 XPath: The functions

42. 42 XPath Function Library Node Set Functions String Functions Number Functions Boolean Functions

43. 43 Node Set Functions

44. 44 String Functions

45. 45 Number Functions

46. 46 Boolean Functions

47. 47 XQL: XML Query Language XQL problem domains Queries, search contexts, and result sets Result sets vs. result documents

48. 48 XQL Introduction Developers –Texcel, webMethods, Microsoft Traditional query processing Features of XML documents

49. 49 Traditional Query Processing Structured query –For relational database –For object-oriented database Unstructured full-text query –For text documents

50. 50 Features of XML Documents As documents As data sources With structure feature

51. 51 XQL Problem Domains Queries within a single document(in a browser or editor) Queries in collections of documents(document assembly in an XML repository) Addressing within or across documents XSL Patterns

52. 52 The Role of a Query Language Different problem domain has different input/output and processing model Common thing –assertion(name,content,value,relationship) Tradeoff –design separate query language for each problem domain –a general-purpose query language for all problem domains

53. 53 SQL vs. XQL SQLXQL The database is a set of tables.The database is a set of one or more XML documents. Queries are done in SQL, a query language that uses tables as a basic model. Queries are done in XQL, a query language that uses the structure of XML as a basic model. The FROM clause determines the tables which are examined by the query. A query is given a set of input nodes from one or more documents, and examines those nodes and their descendants. The result of a query is a table containing a set of rows. The result of a query is a set of XML document nodes, which can be wrapped in a root node to create a well-formed XML document.

54. 54 Simple Query Example Search Context The Heart of Darkness Joseph Conrad Querynovel Result Set The Heart of Darkness Joseph Conrad

55. 55 Why result documents? An XML document is easily parsed with a standard XML parser, so it can be transmitted as a single ASCII stream and parsed by the receiving application. An XML document can be displayed in a standard XML browser. An XML document can be stored in an XML repository. An XML document can be passed on to an XSL processor to perform transformations or do formatting.

56. 56 XML Database

57. 57 What is Native XML Database? Defines a (logical) model for an XML document –The database is specialized for storing XML data Has an XML document as its fundamental unit of (logical) storage –Documents in, documents out Is not required to have any particular underlying physical storage model –May not actually be a standalone database at all

58. 58 Native XML Database Features XML storage Collections –Allow you to query and manipulate those documents as a set Queries –XPath, XQL Updates –Update portions of documents (XUpdate)

59. 59 Native XML Database Products eXist: proprietary/relational ozone: object-oriented Tamino: proprietary/relational Xindice: proprietary X-Hive: object-oriented/relational