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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
