Jon Bosak, Sun MicrosystemsJon Bosak, Sun MicrosystemsLast revised 1997.03.10Last revised 1997.03.10

XML, Java, and the future of the Web

XML, Java, and the future of the Web

Presented and Annotated by Presented and Annotated by

Byung-Hoon KangByung-Hoon Kang

(hoon@cs.berkeley.edu)(hoon@cs.berkeley.edu)

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

HTML and SGML SGMLSGML allows documents to describe their own grammar

HTML HTML hardwires a small set of tags: a single SGML specification

HTML SGML HTML SGML

Extensibility: new tag ? Yes Yes

application change? Needed Independent

Structure: deep nested ? No Yes

Validation: structural validity ? No Yes

SGML and XMLSGML 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 SGML’s extensibility, structure, and validation

DTD is optionally needed for validation

SGML vs. XML vs. HTML HTML SGML XML 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

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

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.

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.

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.

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

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 ?

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

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.

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

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

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