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语义网的逻辑基础 Logical Foundation of the S emantic Web

语义网的逻辑基础 Logical Foundation of the S emantic Web. 主讲： 黄智生 Zhisheng Huang Vrije University Amsterdam， The Netherlands huang@cs.vu.nl 助教： 胡伟 Wei Hu Southeast University whu@seu.edu.cn . 课程时间表 Schedule. 讲座4：语义网与逻辑 Lecture 4: The Semantic Web and its Logics. 语义网的基本思想 RDF/RDFS OWL 语言

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语义网的逻辑基础 Logical Foundation of the S emantic Web

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  1. 语义网的逻辑基础Logical Foundation of the Semantic Web 主讲： 黄智生 Zhisheng Huang Vrije University Amsterdam， The Netherlands huang@cs.vu.nl 助教： 胡伟 Wei Hu Southeast University whu@seu.edu.cn

  2. 课程时间表Schedule

  3. 讲座4：语义网与逻辑Lecture 4: The Semantic Web and its Logics • 语义网的基本思想 • RDF/RDFS • OWL语言 • OWL-DL及其与描述逻辑的关系

  4. 从Google谈起starting from Google

  5. 存在的问题Existing Problems

  6. 我们能不能做得更好？Can we do it better? • 基于语义的搜索Semantics-based search • 概念组合描述 concept combination specification • 指定特定领域 domain specific • 逼近搜索 approximate search • 搜索代理 search agent

  7. 语义网(Semantic Web) • 核心思想:给网络信息赋于确切定义的意义, 即语义。 • „ • The Semantic Web is an extension of the current web in which information is given well-defined meaning, better enabling computers and people to work inco-operation.“[Berners-Lee et al., 2001]

  8. 语义网想做什么？(What the Semantic Web wants to do) • 机器可自动处理 • 机器可理解 Content is machine-understandable if it is bound to some formal description of itself (i.e. metadata).

  9. 万维网: 影响和展望WWW: Its impacts and visions

  10. 网络1.0Web1.0

  11. 网络2.0Web2.0

  12. 对网络3.0的期待Expectations on Web3.0 从字面上看对Web3.0的特征期待： • 新颖性(Novelty)： 它不同于已有的Web1.0和Web2.0的技术，它能提供全新的一代网络服务模式(即为什么不是Web1.0或Web2.0） • 可行性(Achievability)：它在现有的网络环境下，经过努力是可能实现的， 它并不存在不可逾越的技术障碍（即为什么不是Web4.0或更高）。 • 迫切性(Urgency)：它提供网络服务是当前社会迫切需要的，它的技术引入是能够对社会产生重大影响。（即为什么只能是Web3.0）

  13. 网络3.0Web3.0

  14. 网络1.0 – 网络2.0 – 网络3.0Web1.0 – Web2.0 – Web3.0 • 网络1.0： 文件网 • Web1.0: Web of documents • 网络2.0： 人际/社会网 • Web2.0: Web of persons • 网络3.0： 数据网 • Web3.0: Web of data (semantics)

  15. 网络发展整体观

  16. 语义联接的好处：从一个实例说起Advantages of Linked Data

  17. 数据联接的好处：小结 • 现有的网页是供人们阅读的，不便于机器自动处理，数据联接便于机器自动处理 • 文件联接在局部文字上只允许一个链接，而数据联接对局部文字支持多重链接 • 文件联接只提供部分文字链接，而数据联接保证全文链接 • 基于关键词的搜索引擎如Google虽然看起来支持全文检索，但它不能区分同一个词的不同含义，这对于人名，地名等重复性频率较高的问题领域处理尤其困难，而且在许多具体应用领域一词多义的情形比比皆是。

  18. 数据联接的统一概念格式 • 三元组(Triple)方法: <subject, predicate, object> 例子：<zhishengHuang, isStaffof, VrijeUnivAm> • 提供网络资源的描述能力 例子：<http://wasp.cs.vu.nl/~huang, isStaffof, http://www.vu.nl> • 提供语义的唯一标识 • 让数据内容独立于表达形式 • 提供初步的语义推理能力

  19. 为什么推理支持是必要的？ 例子：从ZhishengHuang是自由大学的雇员和自由大学在阿姆斯特丹，能够推出ZhishengHuang在阿姆斯特丹工作。 <ZhishengHuang, isStaffof, VrijeUnivAm> <VrijeUniv, inCity,Amsterdam>, <?x, isStaffof, ?y>,<?y,inCity,?z> -><?x,worksin,?z> =》<ZhishengHuang, worksin, Amsterdam>

  20. 语义网与本体Semantic Web and Ontologies

  21. 五句话介绍语义网的主要思想：Why the Semantic Web？ • 任任何信息系统都需要数据； • 数数据表示要独立于具体的应用和平台，以保证最大程度地可重用； • 采用统一的数据概念表示以保证数据表示独立于具体系统（即可采用Triple/Tuple形式）； • 数数据应能描述网络资源（即要采用RDF/RDFS或其他类似的语言） • 数数据应提供初步的推理支持（即要采用OWL或其他知识表示语言） • （注意；RDF/RDFS/OWL均采用Triple语义模型）

  22. 发展趋势 根据美国著名市场研究公司Gartner的2007五月份报告， 到2012年，70%的公开网页将带有一定程度的语义标注，20%将使用更强的基于语义网的本体。 Gartner (May 2007): "By 2012, 70% of public Web pages will have some level of semantic markup, 20% will use more extensive Semantic Web-based ontologies”

  23. 海量语义数据的一部分Ontologies and Metadata: Billion Triples dataset（十亿三元组数据集） • 雅虎数据 • 东南大学数据 • 马里兰大学 • 英国open大学 • SemWebBase • （DERI) • 维基百科 • 地理名字 • 出版物 • 英文语义词典 • Freebase • 美国政府数据

  24. Linked Data 2009

  25. 一个具体的数据联接的实例http://sindice.com/apiv2/search?q=%22zhisheng%20huang%22&format=atom&page=1&qt=term一个具体的数据联接的实例http://sindice.com/apiv2/search?q=%22zhisheng%20huang%22&format=atom&page=1&qt=term

  26. 一个具体的数据联接的实例http://sindice.com/apiv2/search?q=%22zhisheng%20huang%22&format=atom&page=5&qt=term一个具体的数据联接的实例http://sindice.com/apiv2/search?q=%22zhisheng%20huang%22&format=atom&page=5&qt=term

  27. Falcons

  28. 让数据内容独立于表达形式

  29. More about the Semantic Web • 请见8月29日 星期六的导课 • 09:00-12:00导课1：Introduction to the Semantic Web（Ivan Herman）

  30. HTML标识(HTML Markup) …… <h2>Zhisheng Huang</h2> <b>Affiliation</b>: Department of Computer Science<br> Faculty of Sciences<br> Vrije University Amsterdam<p> <b>Email</b>: huang @ cs.vu.nl<br> <b>Phone</b>: 31-20-4447740(office) …… </html>

  31. XML标注 XML-Annotations <researcher><name>Zhisheng Huang</name> <affiliation> <department>Department of Computer Science</department> <faculty>Faculty of Sciences</faculty> <university>Vrije University Amsterdam</university> </affiliation> <email>huang @ cs.vu.nl</email> <phone id=“office”> (31)-20-4447740</phone> ……</researcher> </html>

  32. Data Structures • 结构化数据Structured Data: • Database • 半结构化数据Semi-structured Data: • HTML, XML, BibTex • 非结构化数据Non-structured Data: • Text

  33. 关系数据库的XML表示XML representation of a relational database <group name=“AI”> <member id=“001”> <name>John</name> <phone>1234567</phone> </member> <member id=“002”> <name>Mary</name> <phone>7654321</phone> </member> ….. </group> AI group

  34. 文件类型定义Document Type Definition(DTD) <!DOCTYPE researcher [ <!ELEMENT researcher (name, affiliation, email, phone)> <!ELEMENT name (#PCDATA)> <!ELEMENT email (#PCDATA)> <!ELEMENT phone (#PCDATA)> <!ATTLIST phone id CDATA #REQUIRED > <!ELEMENT affiliation (department, faculty, university)> … ]>

  35. 数据模型Data Model Name Department has n 1 Phone Researcher Affiliation Faculty eMail University

  36. XML模式XML Schema • The purpose of an XML Schema is to define the legal building blocks of an XML document, just like a DTD.

  37. Why XML Schemas • XML Schemas are extensible to future additions • XML Schemas are richer and more useful than DTDs • XML Schemas are written in XML • XML Schemas support data types • XML Schemas support namespaces

  38. 名字冲突Name Conflicts • Since element names in XML are not fixed, very often a name conflict will occur when two different documents use the same names describing two different types of elements. • If these two XML documents were added together, there would be an element name conflict because both documents contain a same element with different content and definition.

  39. XML名字空间XML NameSpace • Using Namespaces to solve Name Conflicts Examples: • xmlns:namespace prefix="namespace" • xmlns:xsd="http://www.w3.org/2001/XMLSchema"

  40. 可扩展标识语言模式 XML Schema <xsd:element name="reseracher"> <xsd:complexType> <xsd:element name="name" type="xsd:String"/> <xsd:element name="affiliation" type="affil" minOccurs="1" maxOccurs="unbounded"/> <xsd:element name="phone" type="xsd:String"/> <xsd:element name="email" type="xsd:String"/> </xsd:complexType> </xsd:element> <xsd:complexType name="affil"> <xsd:element name= " department" type="xsd:String"/> <xsd:element name= " faculty" type="xsd:String"/> <xsd:element name="university" type="xsd:String"/> </xsd:complexType>

  41. 资源描述框架Resource Description Framework(RDF) Triple: T(subject, attribute, values) Creator Zhisheng http://wasp.cs.vu.nl/sekt/dig/dig.pdf Cees Creator • Metadata is machine understandable information about web resources or anything that has an URI, it is represented as a set of independent assertions: <rdf:Description about="http://wasp.cs.vu.nl/sekt/dig/dig.pdf"> <dc:Creator rdf:ressource="http://www.cs.vu.nl/~huang"/> <dc:Creator rdf:ressource="mailto:ctv@cs.vu.nl"/> </rdf:Description>

  42. RDF: Dublin Core • The Dublin Core provides properties for describing network objects, suitable for use by network search engines. • The Dublin Core is a set of predefined properties for describing documents. • The first Dublin Core properties were defined at the Metadata Workshop in Dublin, Ohio in 1995 and is currently maintained by the Dublin Core Metadata Initiative.

  43. Dublin Core Metadata Initiative • The Dublin Core Metadata Initiative is an open forum engaged in the development of interoperable online metadata standards that support a broad range of purposes and business models. • http://dublincore.org/

  44. Annotating Metadata <rdf:Description rdf:about=…dc-rdf/"> <dc:title> Guidance on expressing the Dublin Core within the Resource Description Framework (RDF) </dc:title> <dc:creator> Eric Miller </dc:creator> <dc:creator> Paul Miller </dc:creator> <dc:creator> Dan Brickley </dc:creator> <dc:subject> Dublin Core; RDF; XML </dc:subject> <dc:publisher> Dublin Core Metadata Initiative </dc:publisher> <dc:contributor> Dublin Core Data Model Working Group </dc:contributor> <dc:date> 1999-07-01 </dc:date> <dc:format> text/html </dc:format> <dc:language> en </dc:language> </rdf:Description>

  45. 资源描述框架模式RDF Schema (RDFS) • RDFS defines vocabulary for RDF • Organizes this vocabulary in a typed hierarchy • Class, subClassOf, type • Property, subPropertyOf • domain, range

  46. RDFS Person subClassOf subClassOf range domain PhDStudent Professor hasSuperVisor type type Prof. Qu Hu，W

  47. Using A Blank Node • Here the blank node stands for the concept of "John Smith's address".

  48. Blank Node Identifiers • Blank nodes must have a name for triple usage. • Blank node identifiers have the form _:name • exstaff:85740 exterms:address _:johnaddress . • _:johnaddress exterms:street"1501 Grant Avenue" . • _:johnaddress exterms:city "Bedford" . • _:johnaddress exterms:state "Massachusetts" . • _:johnaddress exterms:zip"01730" . • If a node in a graph needs to be referenced from outside this context, a URIref is required. • Blank nodes make binary relationships out of an n-ary one (between John and the street, city, etc.).

  49. 资源描述框架模式RDF Schema (RDFS) • RDFS defines vocabulary for RDF • Organizes this vocabulary in a typed hierarchy • Class, subClassOf, type • Property, subPropertyOf • domain, range

  50. 4. Other RDF Capabilities • Containers • Collections • Reification • Structured Values

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