Pengantar Teknologi Web 3
Teknologi Web Client
• Web browser
• HTML / XML / XHTML
• Javascript / VBScript
• CSS
• Flash player
• Java Applet
• ActiveX / Plugin: program yg terintegrasi dgn browser
• Helper: program yg terinstall di client
Pengembangan sisi client
• Local environment (prosesor, browser, memory, vga, dll)
• Tidak ada kontrol oleh web developer
• Memberikan saran kepada user
– Cth: resolusi 1024 x 768
• Memberi pilihan kepada user
– Cth: javascript harus aktif
• Client / user profiling
Pengembangan sisi client
Pilihan client
Pertimbangan Client
• Kebutuhan dan keinginan user berbeda satu dengan yang lain.
• Pengaruh gender, umur, pendidikan, hobi, pengalaman, latarbelakang, budaya, dll.
• User memiliki tujuan, tugas web developer adalah membantu user mencapai tujuannya (download program, akses jadwal, mencetak daftar harga, dll)
Pertimbangan jaringan
• Bandwidth
– Modem = 56KBps; T1 = 1.5MBps
• Latency: waktu yang diperlukan sebuah paket data untuk menempuh jarak yang menghubungkan dua buah sistem
• Utilization, lalu lintas data pada suatu jaringan.
Web Browser
• MS Internet Explorer (Windows)
• Netscape Navigator/Communicator (Windows & Linux)
• Mozila Firefox (Windows & Linux)
• Opera (Windows & Linux)
• Konqueror (Linux)
• lynx, berbasis teks (Linux)
HTML
• Hypertext Markup Language
• Text based
• Menggunakan tag (tanda) <>
• Tujuannya: untuk tampilan di halaman web
• Bahasanya baku
• Ekstensi : .html , .htm
HTML tag
Judul Halaman
Tags vs. elements
• HTML specifies a set of tags that identify structure and content type
– tags are enclosed in < >
•
specifies an image– most tags come in pairs, marking a beginning and ending
• and enclose the title of a page
HTML
Aligning text
• can specify how elements should be aligned (default is left-justified)
– utilize STYLE attribute of tag
• to justify more than one element as a group, use DIV tags
– ell elements enclosed in DIV are formatted similarly
Text styles
• can specify styles for fonts
– … specify bold
– … specify italics
– … specify typewriter-like (fixed-width) font
– … increase the size of the font
– … decrease the size of the font
– … specify a subscript
– … a superscript
–
…
for paragraphs–
… for inline text
• Note: if elements are nested, the order of opening/closing is important! (LIFO)
Font
Lists
• there are 3 different types of list elements
–
- …
•
• can set type of ordering, start index
–
- …
•
–
- …
•
•
Tabel 1 baris 2 kolom
Tabel 2 baris 2 kolom
URL
Hyperlinks
• perhaps the most important HTML element is the hyperlink, or ANCHOR
– …
• where URL is the Web address of the page to be displayed when the user clicks on the link
• if the page is accessed over the Web, must start with http://
• if not there, the browser will assume it is the name of a local file
– …
• causes the page to be loaded in a new window
Hyperlinks - anchor
• for long documents, you can even have links to other locations in that document
– …
• where ident is a variable for identifying this location
– …
• will then jump to that location within the file
– …
• can jump into the middle of another file just as easily
Images
• can include images using IMG
– by default, browsers can display GIF and JPEG files
– other image formats may require plug-in applications for display
•
• again, if file is to be accessed over the Web, must start with http:// (if not, will assume local file)
Frames
• frames provide the ability to split the screen into independent pages
– must define a FRAMESET that specifies the layout of the pages
– actual pages to be displayed must be in separate files
Frame controversy
• frames are probably the most controversial HTML feature
– some people love them, some people hate them
• 2 reasonable uses for frames
– as a navigational aid:
• can divide the screen into a static menu frame and the main frame for navigating a site
• e.g., www.creighton.edu/~davereed
– as a means of separating program input from output:
• can divide the screen into a static man input form frame and the main frame for displaying output
• e.g., www.creighton.edu/~davereed/csc551/JavaScript/story.html
Menu frame
• to create a menu, need to be able to direct links to the main frame
– name the frames in the FRAMESET
– specify the frame name as TARGET in the link
– specify _top as target to return to top level of browser
Content vs. presentation
• most HTML tags define content type, independent of presentation
– exceptions?
• style sheets associate presentation formats with HTML elements
– CSS1: developed in 1996 by W3C
– CSS2: released in 1998, but not fully supported by browsers
– HTML style sheets are known as Cascading Style Sheets, since can be defined at three different levels
• inline style sheets apply to the content of a single HTML element
• document style sheets apply to the whole BODY of a document
• external style sheets can be linked and applied to numerous documents
lower-level style sheets can override higher-level style sheets
Inline style sheets
• Using the style attribute, can specify presentation style for a single HTML element
– within tag, list sequence of property:value pairs
font-family:Courier,monospace
font-style:italic
font-weight:bold
font-size:12pt font-size:large font-size:larger
color:red color:#000080
background-color:white
text-decoration:underline
text-decoration:none
text-align:left text-align:center
text-align:right text-align:justify
vertical-align:top vertical-align:middle
vertical-align:bottom
text-indent:5em text-indent:0.2in
Inline style sheets (cont.)
• more style properties & values
margin-left:0.1in margin-right:5%
margin:3em
padding-top:0.1in padding-bottom:5%
padding:3em
border-width:thin border-width:thick
border-width:5
border-color:red
border-style:dashed border-style:dotted
border-style:double border-style:none
whitespace:pre
list-style-type:square
list-style-type:decimal
list-style-type:lower-alpha
list-style-type:upper-roman
Document style sheets
• inline style sheets apply to individual elements in the page
– can lead to inconsistencies as similar elements are formatted differently
• e.g., might like for all H1 elements to be centered
– inline definitions mix content & presentation
• violates the general philosophy of HTML
Document style sheets
• document style sheets ensure that similar elements are formatted similarly
– can even define subclasses of elements and specify formatting
p.indented defines subclass of paragraphs
• inherits all defaults of
• adds new features
to specify this newly defined class, place class="ID" attribute in tag
• note how "clean" the BODY is
External style sheets
• modularity is key to the development and reuse of software
– design/implement/test useful routines and classes
– package and make available for reuse
– saves in development cost & time
– central libraries make it possible to make a single change and propogate
Modularity & style sheets
• ideally, the developer(s) of a Web site would place all formatting options in an external style sheet
• all Web pages link to that same style sheet for a uniform look
– simplifies Web pages since only need to specify structure/content tags
Web rules of thumb
• HTML provides for lots of neat features,
but just because you can add a feature doesn't mean you should!
– don't add features that distract from the content of the page
use color & fonts sparingly and be careful how elements fit together
e.g, no purple text on a pink background, no weird fonts
use images only where appropriate
e.g., bright background images can make text hard to read
e.g., the use of clickable images instead of buttons or links can slow access
don't rely on window or font size for layout
e.g., font size may be adjusted by viewer, window constrained
don’t be annoying
e.g., no pop-up windows, excessive advertising, silly music
break large document into smaller or provide a menu (either internal or frame)
stick to standard features and test using both IE and Netscape
utilize style sheets to make changes easy & ensure consistency
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