Full HTML for
Given by Tom Scavo at CPS616 Web Technologies on Spring 98. Foils prepared April 25 98
Outside Index
Summary of Material
| HTML: Limitations and Weaknesses |
| Extensible Markup Language (XML), including XSL and XLL |
Dynamic HTML
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Denote Foils where Image Critical
Denote Foils where Image has important information
Denote Foils where HTML is sufficient
denotes presence of Additional linked information which is greyed out if missing
XML and Dynamic HTML
Outline
References
Hypertext Markup Language
History of HTML
HTML Strengths
HTML Shortcomings
Other Weaknesses
Logical vs. Visual Design
Extensible Markup Language
What is XML?
What is SGML?
SGML Example
SGML Example (cont'd)
SGML Applications
XML Compared
XML Design Goals
XML Design Goals (cont'd)
Origins of XML
XML Characteristics
"Hello World!" in XML
XML Language Elements
Document Type Definition
Client/Server Responsibilities
XML Example
XML Example (cont'd)
XML Example (cont'd)
XML Example (cont'd)
Extensible Style Language
XSL Parsers
Extensible Link Language
Uses of XML
Software Tools
Conclusions
Dynamic Hypertext Markup Language
What is DHTML?
Advantages of DHTML
Disadvantages of DHTML
Components of DHTML
HTML 4.0
HTML DTDs
HTML 4.0 Features
Intrinsic Events
Deprecated Elements
The <OBJECT> Tag
Cascading Style Sheets
CSS1 Features
External Styles
Embedded Styles
Document Object Model
Scripting
Implementations of DHTML
Everywhere HTML
Outside Index
Summary of Material
HTML version of Basic Foils prepared April 25 98 
Full HTML Index
| Tom Scavo |
| Northeast Parallel Architectures Center |
| Syracuse University |
| 111 College Place |
| Syracuse, NY 13244-4100 |
HTML version of Basic Foils prepared April 25 98
Full HTML Index
| HTML: Limitations and Weaknesses |
| Extensible Markup Language (XML), including XSL and XLL |
Dynamic HTML
|
HTML version of Basic Foils prepared April 25 98
Full HTML Index
| XML Complete, Steven Holzner [McGraw-Hill, 1998, ISBN 0-07-913702-4] |
| "XML, Java, and the future of the Web", Jon Bosak, Sun Microsystems, 1997 |
| "Weaving a Better Web", S. Mace, U. Flohr, R. Dobson, T. Graham, Byte, March 1998, pp.58-68 |
| NPAC's HTML Resources page, http://www.npac.syr.edu/projects/tutorials/HTML/ |
HTML version of Basic Foils prepared April 25 98
Full HTML Index
HTML version of Basic Foils prepared April 25 98
Full HTML Index
HTML = Hypertext Markup Language
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| HTML 2.0 spec completed in Nov 95 |
| HTML+ and HTML 3.0 never released |
| HTML 3.2 (Jan 97) added tables, applets, and other capabilities (approx. 70 tags) |
| HTML 4.0 spec released in Dec 97 |
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| HTML is simple and thus easy to learn |
| Hyperlinks |
| It is relatively easy to write an HTML parser |
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| Extensibility: HTML does not allow users to define new tags and attributes |
| Structure: HTML can not be used to model hierarchical or object-oriented data structures, such as those found in databases |
| Validation: HTML does not support data validation or check for document structure |
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| HTML supports only the simplest links, that is, one-way links to physical web resources |
| HTML does little to facilitate indexing, searching, and data interchange |
| HTML has weak internationalization |
| HTML has no technical typesetting capability |
| HTML does a poor job of differentiating between presentation and content |
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| The logical design of a document (content) should be separate from its visual design (presentation) |
Separation of logical and visual design
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| HTML mixes the logical with the visual |
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HTML version of Basic Foils prepared April 25 98
Full HTML Index
| XML = eXtensible Markup Language |
| XML is a subset of Standard Generalized Markup Language, but unlike the latter, XML is specifically designed for the web |
| XML is used to define logical document structure |
| XML is not backward compatible with HTML, but the two will coexist for awhile |
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| SGML = Standard Generalized ML |
| A SGML document carries with it a grammar called a Document Type Definition (DTD). The DTD defines the tags and the meaning of those tags |
| Presentation is governed by a style sheet written in the Document Style Semantics and Specification Language (DSSSL) |
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| A simple SGML document with embedded DTD: <!DOCTYPE DOCUMENT [ <!ELEMENT DOCUMENT O O (p*,BIGP*)> <!ELEMENT p - O (#PCDATA)> <!ELEMENT BIGP - O (#PCDATA)> ]> <DOCUMENT> <p>Welcome to <BIGP>XML Style! </DOCUMENT> |
| Optional |
| closing tag |
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| A corresponding DSSSL style sheet: <!DOCTYPE style-sheet PUBLIC "-//James Clark//DTD DSSSL Style Sheet//EN"> (root (make simple-page-sequence)) (element p (make paragraph)) (element BIGP (make paragraph font-size: 24pt space-before: 12pt)) |
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| HTML is a SGML application |
| HTML's DTD is fixed (i.e., HTML is non-extensible) and can safely be ignored |
| XML is also a SGML application, but since XML is extensible, every XML document must be accompanied by its DTD |
| XML offers "80% of the benefits of SGML for 20% of its complexity" |
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| XML is a compromise between the non-extensible, limited capabilities of HTML and the full power and complexity of SGML |
| HTML < XML < SGML |
| (CSS) (XSL) (DSSSL) |
| XML is a kind of SGML Lite! |
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| 1) XML shall be usable over the Internet |
| 2) XML shall support a variety of applications |
| 3) XML shall be compatible with SGML |
| 4) It shall be easy to write programs that process XML documents |
| 5) Optional features in XML shall be kept to the absolute minimum, ideally zero |
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| 6) XML documents should be human-legible and reasonably clear |
| 7) Design of XML should be prepared quickly |
| 8) Design of XML shall be formal and concise |
| 9) XML documents shall be easy to create |
| 10) Terseness in XML markup is of minimal importance |
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| First draft of XML spec released by W3C in Nov 96 (four other drafts published in 1997) |
| The first XML parser (written in Java) released by Microsoft in July 97 |
| Microsoft released version 1.8 of its XML parser (which supports XML 1.0) in Jan 98 |
| W3C finalized the XML 1.0 spec in Feb 98 |
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| The key feature of XML is its extensibility |
XML has been designed for
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| XML is system and vendor independent |
| XML encourages web developers to concentrate on content via abstract markup |
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| An XML document with external DTD: <?xml version="1.0"?> <!DOCTYPE greeting SYSTEM "hello.dtd"> <greeting>Hello World!</greeting> |
| An XML document with embedded DTD: <?xml version="1.0"?> <!DOCTYPE greeting [ <!ELEMENT greeting (#PCDATA)> ]> <greeting>Hello World!</greeting> |
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| Document Type Definition (DTD), which defines the tags and their relationships |
| Extensible Style Language (XSL) style sheets, which specify the presentation of the document |
| Extensible Link Language (XLL), which defines link-handling details |
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| The DTD specifies the logical structure of the document; it is a formal grammar describing document syntax and semantics |
| The DTD does not describe the physical layout of the document; this is left to the style sheets and the scripts |
| It is no mean task to write a DTD, so most users will adopt predefined DTDs |
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| Scenario #1: the server offers the XML document without its DTD, the parser does a syntax check, and the DTD follows if the XML document is "well-formed" |
| Scenario #2: the server checks the XML document against its DTD ("validity") before sending the document to the client |
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| A logical definition of a hyperlink: <LINK> <TITLE>XML Recommendation</TITLE> <URL> http://www.w3.org/TR/REC-xml </URL> <DESCRIPTION> The official XML spec from W3C </DESCRIPTION> </LINK> |
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| A document may have many such links: <DOCUMENT> <LINKS> <LINK>...</LINK> <LINK>...</LINK> ... </LINKS> </DOCUMENT> |
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| Now write a DTD for this document: <!ELEMENT DOCUMENT (LINKS)> <!ELEMENT LINKS (LINK)*> <!ELEMENT LINK (TITLE,URL,DESCRIPTION)> <!ELEMENT TITLE (#PCDATA)> <!ELEMENT URL (#PCDATA)> <!ELEMENT DESCRIPTION (#PCDATA)> |
| PCDATA stands for "parsed character data" |
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| Store the DTD in a file (links.dtd) and write an XML document based on this DTD: <?XML version="1.0"?> <!DOCTYPE DOCUMENT SYSTEM "links.dtd"> <DOCUMENT> <LINKS> <LINK>...</LINK> <LINK>...</LINK> ... </LINKS> </DOCUMENT> |
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| XSL is to XML as Cascading Style Sheets (CSS) are to HTML |
| Like a CSS, an XSL style sheet describes the presentation of the XML document |
| Advanced layout features of XSL include: rotated text, multiple columns, and independent regions |
| Development of XSL lags behind XML |
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| XML |
| source |
| XSL |
| style |
| XSL |
| parser |
| HTML |
| source |
| Microsoft has released two XSL processors: 1) a command-line utility that takes an XML document and an XSL style sheet, and gives an HTML document; and 2) an ActiveX control for displaying XML in a browser (namely, IE4.0) |
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XLL supports simple links (like HTML) plus:
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| XLL components: XLink and XPointer |
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| Applications requiring client to mediate between two heterogeneous databases |
| Applications that attempt to redistribute processing load from server to client |
| Applications requiring client to present multiple views of same web document |
| Applications that perform or require detailed, domain-specific search results |
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| An XML parser (in Java or C++) and an XSL parser are available from Microsoft |
| Internet Explorer 4.0 supports XML |
| An HTML browser may be retrofitted with an XML plugin or applet, but if XML is to survive, full-fledged XML browsers must be developed |
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| Coupled with XSL, DOM, and a scripting language, XML provides a powerful alternative to HTML |
| Search engines may make better use of XML documents |
| Prediction: XML will replace HTML! |
| Few browsers support XML at this time, whereas DHTML is here now |
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HTML version of Basic Foils prepared April 25 98
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| DHTML = Dynamic HTML |
Capabilities of DHTML:
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| It is available now |
| It is an extension of HTML and therefore familiar |
| It addresses many of HTML's shortcomings |
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| There is no standard for DHTML (Netscape and Microsoft are pushing their respective implementations for W3C ratification) |
| In the long run, XML will most likely replace HTML, so why learn DHTML? |
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DHTML consists of the following:
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| The final spec for HTML 4.0 was released by W3C in December 1997 |
There are three flavors:
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| HTML 4.0 has 93 elements (10 deprecated) and 187 attributes (49 deprecated) |
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| Version 3.2 DTD: <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"> |
| Version 4.0 DTDs: <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN" "http://www.w3.org/TR/REC-html40/strict.dtd"> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" "http://www.w3.org/TR/REC-html40/loose.dtd"> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Frameset//EN" "http://www.w3.org/TR/REC-html40/frameset.dtd"> |
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| More multimedia options |
| Better printing facilities |
| Better table support, especially long tables |
| Internationalization and accessibility |
| Style sheets and scripting languages |
| Intrinsic events |
| Embedded and linked documents |
| A new <BUTTON> tag |
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| Most JavaScript 1.2 event handlers (except onAbort, onError, and the new window event handlers) are native to HTML 4.0 |
| The <SCRIPT> tag is fully supported |
| A <NOSCRIPT> tag has been added |
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| Some elements (tags) of HTML 3.2 have been deprecated in 4.0, including: <FONT>, <BASEFONT>, <CENTER>, <S>, and <U> |
| Numerous attributes have been deprecated, including: ALIGN, BACKGROUND, BGCOLOR, LINK, COLOR, and SIZE |
| The <APPLET> tag has been deprecated! |
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| Instead of <APPLET CODE="MyApplet.class" WIDTH=200 HEIGHT=300></APPLET> in HTML 4.0 we write <OBJECT CLASSID="MyApplet.class" CODETYPE="application/java" WIDTH=200 HEIGHT=300></OBJECT> |
| The <PARAM> tag is still supported |
| Nested objects are allowed |
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| Cascading Style Sheets (CSS1) allow more precise and consistent layout |
| Style sheets permit pages to inherit properties from other pages--in effect, they permit object-oriented document structure |
| CSS2 is coming, including aural rendering of web documents (for sight-impaired users, in-car applications, language instruction) |
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| Flexible placement of style information |
| Independence from specific style sheet languages |
| Cascading style sheets |
| Media dependencies |
| Alternate styles |
| Performance concerns |
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| A simple style sheet (in file "myStyle.css"): P.special { color: red; border: solid black; } |
| Now put a <LINK> tag in the <HEAD>: <LINK href="myStyle.css" rel="stylesheet" type="text/css"> |
| In the <BODY>, type: <P class="special">A special paragraph! |
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| Read in a style sheet and override a style: <HEAD> <STYLE type="text/css"> @import url(myStyle.css); H1 {text-align: center} </STYLE> </HEAD> |
| Color a paragraph (not recommended): <P STYLE="color: green">A green paragraph! |
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DOM defines a platform-independent programmatic interface to web documents:
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| Initially, DOM will be bound to ECMAScript |
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Current versions of scripting languages:
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ECMAScript is an ECMA standard (6/97)
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Differences between Microsoft and Netscape implementations of DHTML:
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| A wysiwyg HTML editor called NetObjects Fusion generates dynamic web pages in "Everywhere HTML" |
| By using a combination of HTML, CSS-positioning and JavaScript, pages written in Everywhere HTML work properly on both Internet Explorer 4.0 and Communicator 4.0 (or so it is claimed) |