dorit
Uploaded by
65 SLIDES
857 VUES
650LIKES

Chapter 3

DESCRIPTION

Chapter 3. Web Technology. Web Publishing. Static documents HTML, ASCII text, Postscript, PDF GIF, JPEG, MOV, Quicktime, AVI AU, WAV, MP3, RealAudio Dynamic documents executable content Java, Javascript, Active-X, Dynamic HTML Variable documents Dynamically-generated (on-the-fly)

1 / 65

Télécharger la présentation

Chapter 3

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 3 Web Technology

  2. Web Publishing • Static documents • HTML, ASCII text, Postscript, PDF • GIF, JPEG, MOV, Quicktime, AVI • AU, WAV, MP3, RealAudio • Dynamic documents • executable content • Java, Javascript, Active-X, Dynamic HTML • Variable documents • Dynamically-generated (on-the-fly) • CGI, FastCGI, JSP, PHP

  3. HyperText Markup Language • Document structure description • (sub-)sections • headings • tables • No (?) layout information • style sheets • font mapping • Defined in SGML / XML (XHTML) • Document Type Definition (DTD)

  4. HTML Basic Elements • <HTML> • <HEAD> • <TITLE>Hello World</HTML> • </HEAD> • <BODY> • Oh, what a beautiful morning.... • </BODY> • </HTML>

  5. HTML Elements • physical text styles • logical test styles • test segmentation • tables • inline pictures • anchors/links • forms • specials • image maps (client/server) • background pic/audio, marquees

  6. HTML Development • Browser war (NS Navigator vs. MSIE) • World Wide Web Consortium (W3C) • rendering • internationalization • forms • active content • object models

  7. HTML History • HTML 2.0 • 1st version conforming to SGML • Core HTML (lists, forms, headings, fonts, image maps, ...) • HTML 3.2 (no HTML 3.0 & HTML 3.1) • many elements get additional attributes • font sizes, font faces, colors • form-based file upload • client-side image maps • tables, APPLET tag • STYLE and SCRIPT tags (placeholders, no exact mechanisms)

  8. HTML 3.2 • Script Tags • JavaScript, VBScript, Jscript • eventless • APPLET tag • Styles (CSS) • ALIGNs generalized • client-side image-maps • FONT • formulas • FORM based file upload

  9. HTML 4.0 • accessability • labels, legend, clusters • iterators, access keys • character encodings, language codes (lang) • bidrectional text (dir) • incremental rendering • tables, images • objects (nested) • scripts and events • frames

  10. HTML 4.0 (Frames) • TARGETs <A href="slide2.html" target="dynamic">slide 2.</A> • IFRAMEs <IFRAME src="foo.html" width="400" height="500" scrolling="auto" frameborder="1"> [Your user agent does not support frames] </IFRAME>

  11. HTML 4.0 (Scripts) • client-side execution at • loading • user input (focus, pointer movement) • language selection • <META http-equiv="Content-Script-Type" content="type"> • <SCRIPT type="text/vbscript" src="http://someplace.com/progs/vbcalc"> • </SCRIPT> • evaluation order, object modification (DOM)

  12. HTML 4.0 (Events) • Loading • onload, unload • Pointer • onmousemove, onmousmoveover, ... • Keyboard • onkeypress, onkeydown, ... • Form handling • onsubmit, onreset, onselect, onchange • <INPUT NAME="userName" onblur="validUserName(this.value)">

  13. HTML 4.01 • Common attributes for many elements: Id, Title, Style, Class • Improved tables (Thead, Tbody, Tfoot, column handling, formatting), Incremental rendering of tables • Improved forms • STYLE element now encloses style sheet instructions (CSS) • Style sheets: separation of content and styles (CSS)

  14. HTML 4.01 • Frames, Embedded documents (IFRAME) • APPLET element deprecated (OBJECT) • Intrinsic events (onclick, ondblclick, onmouseover, onmouseout, ...) • OBJECT element (IMAGE, APPLET, IFRAME) • SCRIPT element (client-side scripting - JavaScript, VBScript, ...)

  15. <OBJECT data="http://some.server.com/me.png" type="image/png"> A picture of me. </OBJECT> <OBJECT codetype="application.java" classid="java:AudioItem.start codebase="http://some.server.com/java/AudioStuff/" width="15" height="15"> <PARAM name="sound" value="Welcome.au"> Play a welcoming sound. </OBJECT> <OBJECT data="embed_me.html"> Warning: embed_me.html could not be embedded. </OBJECT> OBJECT Element Examples

  16. More OBJECT examples <OBJECT data="canyon.png" type="image/png"> This is a <EM>closeup</EM> of the Grand Canyon. </OBJECT> <OBJECT classid="http://www.miamachina.it/clock.py"> An animated clock. </OBJECT> <OBJECT data="embed_me.html"> Warning: embed_me.html could not be included. </OBJECT>

  17. Client-side Scripting 1 • Languages: JavaScript, VBScript, Python, Tcl, ... • Security ?

  18. <SCRIPT type= " text/vbscript" src="http://someplace.com/vbcalc"> </SCRIPT> <INPUT NAME="userName" onblur="validUserName(this.value)"> <INPUT NAME="edit1" size="50"> <SCRIPT type="text/vbscript"> Sub edit1_changed() If edit1.value = "abc" Then button1.enabled = True Else button1.enabled = False EndIf EndSub </SCRIPT> Client-side Scripting 2

  19. <INPUT NAME="num" onchange="if (!checkNum(this.value, 1, 10)) { this.focus(); this.select(); } else {thanks()}" VALUE="0"> <BUTTON type="button" name="mybutton" value="10"> <SCRIPT type="text/javascript"> function my_onclick() { ... } document.form.mybutton.onclick = my_onclick </SCRIPT> </BUTTON> Client-side Scripting 3

  20. Cascading Style Sheets • Separation of content (HTML, XML documents) and presentation style (CSS) • simplified Web authoring • easier Web site maintenance • CSS vs. XSL • CSS was defined earlier • XSL is still a draft while CSS is already supported by browsers • XSL is more powerful => too complex for many users/applications

  21. <HTML> <HEAD> <STYLE TYPE="text/css"> H1 { color: yellow; font-style: italic; font-family: helvetica } .verde { color: #00FF00 } </STYLE> </HEAD> <BODY> <H1>Heading 1</H1> <H2 class="verde">Heading 2</H2> <P STYLE="color: red"> paragraph text </P> yet another paragraph </BODY> </HTML> Heading 1 Heading 2 paragraph text yet another paragraph Style and HTML

  22. <HTML> <HEAD> <TITLE>Document with Cascading Style Sheets</TITLE> <LINK rel="alternate stylesheet" title="compact" href="small-base.css" type="text/css"> <LINK rel="alternate stylesheet" title="compact" href="small-extras.css" type="text/css"> <LINK rel="alternate stylesheet" title="big print" href="bigprint.css" type="text/css"> <LINK rel="stylesheet" href="common.css" type="text/css"> </HEAD> <BODY> ... </BODY> </HTML> @import "fineprint.css" print; @import url("bluish.css") projection, tv; External CSS and Cascasding

  23. Without Style

  24. Better do it stylish !

  25. BODY { background: #def url("recbg.jpg"); color: black; margin: 0.5em; } A:link { color: #00ff00; } A:visited { color: #0000ff; } TABLE.navigation { border-style: none; } TD.navigation { background: black; text-align: center; font-weight: bold; font-family: helvetica, sans-serif; padding: 0.2em; vertical-align: top; } <HTML> <HEAD> <LINK rel="STYLESHEET" href="MyStyle.css" type="text/css"> </HEAD> <BODY> <TABLE class="navigation" COLS=4> <TR> <TD class="navigation"> <A HREF="...">Previous</A></TD> ... CSS by Example (1/3)

  26. H1, H2, H3, H4, H5, H6 { font-family: helvetica, sans-serif; text-align: left; font-weight: normal; font-style: italic; } H1 { font-weight: bold; font-style: normal; } DIV.quote { text-align: right; font-style: italic; color: blue; } LI { list-style: square; } <H1>Heading 1</H1> <DIV class="quote"> He brewed a song of love and ... </DIV> <H2>Heading 2</H2> <H3>Heading 3</H3> <UL> <LI>item 1</LI> <LI>item 2</LI> </UL> CSS by Example (2/3)

  27. DIV.listing { border: solid thin; margin-top: 0.5em; margin-right: 1.5em; margin-left: 1.5em; margin-bottom: 0.5em; background: white; } SPAN.ltitle { text-align: center; font-family: helvetica, sans-serif; font-style: normal; font-weight: bold; font-size: 100%; margin-top: 0.25em; } DIV.warning { border: solid thick; border-color: red; margin-top: 0.5em; margin-right: 1.5em; margin-left: 1.5em; margin-bottom: 0.5em; } CAPTION { text-align: center; color: #088; font-style: italic; font-weight: bold; font-size: 100%; } <DIV CLASS="listing"> <SPAN CLASS="ltitle">C shell</SPAN> <HR> <PRE> setenv CVSROOT /path/to/CVS cvs checkout Project </PRE> </DIV> <CAPTION>Figure 1: This ...</CAPTION> <DIV CLASS="warning"> This is a warning! </DIV> CSS by Example (3/3)

  28. Extensible Markup Language • XML (1998) is an application of SGML • Standard Generalized Markup Language (1986): ISO8879 • influenced by HTML (SGML Document Type Definifion) • Structure description language • Meta-language: language to describe other languages • Tags enclose identifiable parts of a document • markup (type-setting systems)

  29. XML Example <warning> <para>This substance is <emph>hazardous</emph> to health</para> <para>See procedure 12A.7 for information on protective clothing.</para> <image .../> </warning>

  30. XML Documents Document Document Unit Sub-unit

  31. <!ELEMENT warning (para*, image?)> <!ELEMENT para (#PCDATA | emph)*> <!ELEMENT image EMPTY> <!ATTLIST image url CDATA #REQUIRED> <!ELEMENT emph (#PCDATA)*> Document Type Definition • DTD defines the elements allowed • A parser compares the DTD rules against a given XML document => validation • XML DTDs can be applied for data-type definitions (XML-RPC), data exchange (EDI, push, RDBMS), etc.

  32. <warning> <para>This substance is <emph>hazardous</emph> to health</para> <para>See procedure 12A.7 for information on protective clothing.</para> <image .../> </warning> XML Document Presentation • Style sheets specify output format • 1 XML document, n alternative style sheets depending on audience, media, etc. WARNING: This substance is hazardous to health See procedure 12A.7 for information on protective clothing.

  33. <!-- DTD for user groups in JSEF --> <?xml encoding="US-ASCII"?> <!ELEMENT usergroups (user)*> <!ATTLIST usergroups lastChanged CDATA #REQUIRED changedBy CDATA #REQUIRED> <!ELEMENT user (addgroups | subgroups)*> <!ATTLIST user userName ID #REQUIRED> <!ELEMENT addgroups (group)+> <!ELEMENT subgroups (group)+> <!ELEMENT group EMPTY> <!ATTLIST group groupName CDATA #REQUIRED> XML by Example (1/2)

  34. <?xml version="1.0"?> <!DOCTYPE usergroups SYSTEM "usergroups.dtd"> <usergroups lastChanged="10/21/1999" changedBy="sysadmin"> <user username = "Charly Brown"> <addgroups> <group groupname = "User" /> <group groupname = "InternalUser" /> </addgroups> <subgroups> <group groupname = "Developer" /> </subgroups> </user> <user username = "Hugo Boss"> <addgroups> <group groupname = "Admin" /> </addgroups> </user> </usergroups> XML by Example (2/2)

  35. Extensible Stylesheet Language • XSL is a language for expressing stylesheets and consists of • a language for transforming XML documents (XSLT) • an XML vocabulary for specifying formatting semantics (Formatting Objects DTD - FO DTD) • CSS < XSL < DSSSL (SGML's Document Style Semantics and Specification Language) • Style sheets • target specific elements => closely related with DTDs

  36. XSL and XSLT Processing XSL processor XSLT stylesheet XSLT processor source DTD document new document FO DTD

  37. Document Reengineering • analysis • data sources, responsibilities and update dynamics • data model • EER (extended entity-relationship model) • mapping logical -> physical • reverse association: how to link back • forward association: how to link forward

  38. HTML Code Creation • Editors • Tags, Syntax • Validators • Halsoft, htmllint, .... • Converters • which HTML? DTD as parameter • how to map the document structure into HTML? • special symbols? mathematical formulas? • what happens with hyperlinks in original document?

  39. HTML Creation (cont'd) • Development Environments • versioning • staging • TODO database • link consistency • upload to server • integration of functionality • CGIs • backend applications, databases • client-side scripting

  40. Webserver State maintenance • HTTP interactions are "isolated", i.e., HTTP does not include means to hand over state information between interactions -> difficult • Advanced web applications, e.g. shopping basket, require that state can be shared between interactions (between web client and web server) • External apps have their own state space

  41. WWW Gateways HTTP Web browser Web server CGI (HTTP) WWW CGI gateway Gateway-specific protocol non WWW Application

  42. Stateful Gateways • A permanently running gateway process keeps up a connection with the external application and serves successive HTTP requests, i.e. the gateway maintains the session’s state. • Problem: state bookkeeping • client caches • back button • interrupted requests (recover ?) • time-out for follow-up requests (bound resources ?) • Example: DBs (expensive login)

  43. Stateless Gateways • Gateway or external application generate state-information which is stored at the client and sent with every request. • State can be stored in • URLs • hidden fields • Cookies • Solve state consistency problem ?

  44. http://some.host.org/gateway.pl?user=hugo&items=4711+0815+...http://some.host.org/gateway.pl?user=hugo&items=4711+0815+... <FORM METHOD="POST" ACTION="/gateway.pl"> <INPUT TYPE="HIDDEN" NAME="user" VALUE="hugo"> <INPUT TYPE="HIDDEN" NAME="items" VALUE="4711+0815+..."> ... State in URLs / Hidden Fields • State information can become large • User can change state information (reservation ?) • Sessions may have to be replayed until the state for the next step is reached • Unreadable URLs are no solution • Passwords ?

  45. Cookies • A cookie is a small data structure which holds name, value pairs which is sent back and forth between web client and web server for certain URLs • Several incompatible "standards" • original standard by Netscape (Set-Cookie) • RFC 2109 (Set-Cookie) • New Internet Draft (Set-Cookie2)

  46. Set-Cookie: Basket="4711+0815"; Version="1"; Max-Age="3600"; Path="/cgi-bin/order"; Domain=".supershop.com" Cookie: $Version="1"; Basket="4711+0815"; $Path="/cgi-bin/order"; $Domain=".supershop.com" Cookie example User shops around and gathers 2 items in his shopping basket (server -> client): User decides to buy the 2 items and selects http://www.supershop.com/cgi-bin/order/buy.pl (client -> server)

  47. .netscape.com TRUE / FALSE 946684799 NETSCAPE_ID 100103 More about Cookies • Cookies can enhance or break privacy • tracking vs. no user database • Cookies are kept in memory • Persistent cookies: cookies[.txt] file creator (domain) path expiration name value access for all hosts in domain ? require secure connection ?

  48. httpd.conf: AddType text/html .shtml AddHandler server-parsed Options ... Include ... Server-side Includes • .shtml files are parsed for special commands • executed before the file is sent to the client

  49. <!--#element attribute=value attribute=value ... --> SSI Syntax Main elements Variables (additionally to CGI environment variables) DATE_GMT, DOCUMENT_NAME, DOCUMENT_URI, LAST_MODIFIED Flow control <!--#if expr="test condition" --> <!--#elif expr="test condition" --> <!--#else --> <!--#endif -->

  50. SSI problems • Performance • parsing • command execution • Security • exec command, etc. • IncludesNoExec • Unreadable -> maintenance ?

More Related