Jon%20Bosak,%20Sun%20Microsystems%20Last%20revised%201997.03.10 - PowerPoint PPT Presentation

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Jon%20Bosak,%20Sun%20Microsystems%20Last%20revised%201997.03.10

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For example, XSL can be used to transform XML data into HTML/CSS documents ... To render XML in XML-support-browser : CSS or XSL ... – PowerPoint PPT presentation

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Title: Jon%20Bosak,%20Sun%20Microsystems%20Last%20revised%201997.03.10


1
XML, Java, and the future of the Web
  • Jon Bosak, Sun MicrosystemsLast revised
    1997.03.10

Presented and Annotated by Byung-Hoon
Kang (hoon_at_cs.berkeley.edu)
2
RoadMap
  • Part1 Why XML ?
  • HTML and SGML
  • SGML and XML
  • SGML vs. XML vs. HTML
  • Part2 Example applications
  • Example applications envisioned in 1997
  • Database interchange problem
  • Why solution is not feasible in HTML
  • XML solution envisioned in 1997
  • Part3 Why CSS/XSL ?
  • What are style sheet and why?
  • Style sheet languages
  • Why two style sheets language for XML ?
  • Conclusion XML,DTD,CSS and XSL

3
HTML and SGML
  • SGML allows documents to describe their own
    grammar
  • HTML hardwires a small set of tags a single SGML
    specification

  • HTML SGML
  • Extensibility new tag ? Yes
    Yes
  • application change? Needed
    Independent
  • Structure deep nested ? No
    Yes
  • Validation structural validity ? No
    Yes

4
SGML and XML
  • SGML
  • Contains many optional features not needed for
    Web applications
  • Cost/benefit ratio unattractive to current
    vendors of Web browsers
  • DTD is required all the time
  • XML
  • A simplified subset of SGML for Web applications
  • Retain SGMLs extensibility, structure, and
    validation
  • DTD is optionally needed for validation

5
SGML vs. XML vs. HTML

  • HTML SGML XML
  • Extensibility new tag ? Yes/No
    Yes Yes
  • Structure deep nested ? No
    Yes Yes
  • Validation structural validity ? No
    Yes Yes
  • DTD is required for parsing ? No
    Yes Opt.
  • Browser dependency ? High
    Low Low
  • Cost/Benefit ?
    Good Poor Med
  • When were you born ? 92
    86 98

6
RoadMap
  • Part2 Example applications
  • Example applications envisioned in 1997
  • Database interchange problem
  • Why solution is not feasible in HTML
  • XML solution envisioned in 1997
  • Part3 Why CSS/XSL ?
  • What are style sheet and why?
  • Style sheet languages
  • Why two style sheets language for XML ?
  • Conclusion XML,DTD,CSS and XSL

7
XML applications envisioned in 1997
  • to mediate between two or more heterogeneous
    databases.
  • to distribute a significant proportion of the
    processing load from the Web server to the Web
    client.
  • to present different views of the same data to
    different users.
  • to tailor information discovery to the needs of
    individual users.

8
Database interchange the universal hub
  • The information tracking system for a home health
    care agency
  • Need to key-in all of patient medical histories
    and billing data from a variety of doctors,
    hospitals, pharmacies, and insurance companies.
  • 1. Log into the hospital's Web site.
  • 2. Become an authorized user.
  • 3. Access the patient's medical records using a
    Web browser.
  • 4. Print out the records from the browser.
  • 5. Manually key in the data from the printouts.

9
Database interchange the universal hub
  • A real solution would look more like this
  • 1. Log into the hospital's Web site.
  • 2. Become an authorized user.
  • 3. Access the patient's medical records in a
    Web-based interface that represents the records
    for that patient with a folder icon.
  • 4. Drag the folder from the Web application over
    to the internal database application.
  • 5. Drop it into the database.

10
Why solution is not feasible in HTML ?
  • HTML tag set is too limited
  • to represent or differentiate between the
    multitude of database fields
  • hard to automate the process
  • HTML is incapable of representing the variety of
    structures in those documents.
  • HTML lacks mechanism in checking the data for
    structural validity

11
XML solution envisioned in 1997
  • 1. Form a standards consortium for Health Care
    Markup Language and its HCML.DTD
  • 2. Adopt a single industry-wide interchange
    format that serves as the single output format.
  • 3. Use any standard application to validate and
    process HCML marked-up data with HCML.DTD
  • Similar to the steps in traditional SGML usage
  • Still have the same problem of standardization.
  • Is XML advantageous than SGML in doing steps 1, 2
    or 3 ?

12
RoadMap
  • Part3 Why CSS/XSL ?
  • What are style sheet and why?
  • Style sheet languages
  • Why two style sheets language for XML ?
  • Conclusion XML,DTD,CSS and XSL

13
What are style sheets and Why?
  • Style sheets
  • Describe how documents are presented on screens,
    in print or in audio.
  • Detach the formatting information from data
    source in document
  • Why want to influence the presentation of
    documents
  • without sacrificing device-independence or
  • adding new HTML tags.

14
Stylesheets
  • DSSSL (Document Style Semantics and Specification
    Language) for SGML
  • DSSSL-online the subset of DSSSL for SGML
    online.
  • CSS (cascading style sheets)
  • provides a style mechanism well suited to the
    relatively low-level demands of HTML
  • currently used a little bit
  • XSL (extensible style language)
  • needed to present XML document on the browser.
  • transformational functionality

15
Why two Style Sheet languages?
  • CSS
    XSL
  • Can be used with HTML? yes no
  • Can be used with XML ? yes yes
  • Transformation language? no yes
  • Syntax ? CSS XML
  • CSS need to be used to style HTML documents
  • XSL, on the other hand, is able to transform
    documents
  • For example, XSL can be used to transform XML
    data into HTML/CSS documents
  • Both languages can be used to style XML documents

16
Conclusion XML, DTD, CSS and XSL
  • To validate XML structural input DTD
  • To exchange data using XML None or DTD for
    structural validation
  • To standardize the data exchange model Still
    need to form a consortium
  • To render XML in XML-support-browser CSS or XSL
  • To render XML in HTML-support-browser Use XSL
    to transform XML into HTML/CSS
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