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Why XML and Web Technologies

Why XML and Web Technologies. Speaker: 呂瑞麟 國立中興大學資管系教授 Email: jllu@nchu.edu.tw URL: http://web.nchu.edu.tw/~jlu. Two Facts Millions of computers are inter-connected We are overwhelmed by data One Question Are they fully utilized?.

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Why XML and Web Technologies

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  1. Why XML and Web Technologies Speaker: 呂瑞麟 國立中興大學資管系教授 Email: jllu@nchu.edu.tw URL: http://web.nchu.edu.tw/~jlu

  2. Two Facts • Millions of computers are inter-connected • We are overwhelmed by data • One Question • Are they fully utilized?

  3. Distributed Systems or Distributed Computing • A distributed system is one in which components located at networked computers communicate and coordinate their actions only by passing messages (依據 Coulouris et al. 的定義) • A distributed system is a collection of independent computers that appears to its users as a single coherent system (依據 Tanenbaum and Steen的定義) • In traditional distributed systems, the number of participating nodes is much smaller and controlled, compared to Internet-scale systems such as Web.

  4. Goals • Distributed Computing 解決第一個問題 • Sharing of resources including files, printers, processing power, memory, etc. • Well-integrated (as one system or service) • intelligent • Secured • … • How about data? • DATA (information, knowledge) • Examples: the Web

  5. Examples of Distributed Systems • The Internet • Computers interact by message passing • Services (WWW, FTP, emails) can be added, replaced, or removed freely • Intranets, P2P, Mobile and Ubiquitous Computing • World Wide Web • Cloud Computing

  6. The Web • 不論從系統的角度，或者是資料的角度，似乎都無法忽略，甚至與 Web 緊緊相連 • 讓我們從 WWW 的發展過程，看看能不能找出一些端倪！

  7. World Wide Web (I) • History: ftp  gopher  WWW • Tim Berners-Lee at European Center for Nuclear Research (CERN) in 1998 • Driven forces: • sharing (collaboration), • publishing (easy to find), • simplicity (HTML), • Openness • Links (hypertext structure) Linked Open Data

  8. Hypertext • An approach to information management in which data are stored in a network of documents connected by links. • The promise of hypertext lies in its ability to produce large, complex, richly connected, and cross-referenced bodies of information. • The needs for hypertext • Information in enterprises is seldom located on one node or server • Accessing and retrieving large monolithic documents is time consuming. A good strategy is to split them into smaller pieces to reduce user waiting and network utilization time. • Reuse of document fragments for composing new documents

  9. Hypertext vs. Hypermedia • Hypermedia • Often, the terms hypertext and hypermedia are used interchangeably, causing confusion. Think of hypermedia as hypertext and more (a sort of like hypertext++) and referring to the ability to use several media (text, graphics, sound, video) in a single document.

  10. Is WWW = Hypermedia? • Bieber et al. described many hypermedia features lacking or poorly supported on the Web. (M. Bieber, F. Vitali, H. Ashman, V. Balasubramanian, and H. OinasKukkonen, “Fourth generation hypermedia: some missing links for the World Wide Wed,” Journal of Human Computer Studies, vol. 47, 1997, pp. 31-65) • Bi-directional Links, one-to-many links, etc. • Many believe that the current Web implementation of hypermedia inhibit the true potential for hypermedia’s relationship management and navigation to augment WIS.

  11. World Wide Web (II) • Design Problems: • Link integrity: ‘dangling links’ • The nodes being linked may be owned and changed independently of the nodes linking to them. (lack of standard mechanisms for notifying remote sites about changes to local sites) • First-class links, Meta-level links, XLink, etc. • Referencing pages from a disparate collection of sources • lacks of reliability

  12. World Wide Web (III) • Design Problems : • Too many search results • lacks of metadata • Google annotation(?) • Web data is for human, what about for machines? • Semantic Web: an extension of the current web in which information is given well-defined meaning, better enabling computers and people to work in cooperation

  13. World Wide Web (IV) • Challenges: • Viewing WISs as DB applications • Extract structure/schema information from heterogeneous sources such as files, WAIS, HTML, … • Indexing and mining • Create indexes when data structure is unknown. • Query (for end users, query languages are hard) • WebOQL (G. Arocena and A. Mendelzon, “Viewing WISs as Database Applications,” CACM, vol. 41, no. 7, 07/1998, pp. 101-102) • Do not require pre-defined schema which makes it possible to query

  14. World Wide Web (V) • Challenges: • Better Browser Support • (partly answered by Google Chrome?) • Today, most of what we use the Web for on a day-to-day basis aren’t just web pages, they’re applications. • DIFFERENT FROM WHAT THEY WERE FIRSTLY CREATED. • Major changes: • Better Javascript engine • Better Integration • Service-Oriented Architecture (SOA): for example, Web services

  15. Summary • A tremendous amount of resources is available on WWW. • WWW is also a kind of distributed systems. • XML is a great enabling technology • message passing (or data interchange) • good for describing resources

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