1. How the World Wide Web works
Barend Köbben
International Institute for Geo-information Science and Earth Observation (ITC)

2. History of the Web (1969) start of ARPAnet
(1983) ARPAnet, USEnet en EUnet adopt TCP/IP communication: birth of the Internet
many protocols run “on top of” TCP/IP (telnet, ftp, smpt)
because of IP-adressing all networks can can be seen as one big network
(1991) definition of the WWW-protocols:
HTTP: HyperText Transfer Protocol
HTML: HyperText Markup Language

3. IP-adressing & DNS (domain name servers)
INTERNET
SURFNET
admin nl-domain: xx.xx.nl
DNS aliasing
ITC router
admin ITC- domain: xx.itc.nl
NVK server
= kartoweb.itc.nl

4. (Explorer, Netscape, Opera)
HTTP communication
Client-server architecture
Client
Server
Can I have that file?
Webserver
(IIS, Netscape, HTTPd)
Browser
(Explorer, Netscape, Opera)
Here it is...

5. HTML code
<P>Hello<B>World</B><HR>How are<I>you</I>?<P><A HREF= ”otherfile.html”>Click here</a> to go.
Looks like:
Hello World
How are you?
Click here to go.

6. Standard configuration
GET file.gif
GET file.html
PUT file.gif
PUT file.html
<img src = “file.gif”> <br> <i>STATIC </i> MAP
file.gif
/file.html
STATIC MAP

7. Constraints Standard configuration offers: HTTP communication-protocol
HTML–, GIF– en JPEG–formats
Static maps only
No interactivity (except “clickable maps”)
Overcoming the constraints:
Only possible by adding data-formats and protocols
Possible loss of platform independency

8. Plugins (client-side)
PDF-READER
<img src = “file.pdf”> <br><i> interactive </i> map
file.pdf
interactive map

9. Java applets (client-side)
Java Virtual Machine
map applet
Java- applet
code
map.class
<applet src = “map.class”> <br> map applet

10. JavaScript (client-side)
Java Virtual Machine
<script >
<!--
Document.write(“map”); }
//-->
</script>
map

11. CGI–applications (server-side)
/CGI?makemap &title=“itc”
itc
CGI- APPLI-CATION

12. Active Server Pages (server-side) handles JavaScript or VBscript
Microsoft IIS
database stuff
HTML
in memory
<img src = map.gif> <br>database stuff
server-plugin (asp.dll)
<img src = <% foundrecords.image %> <br>database stuff a

13. Java servlets (server-side)
Java Virtual Machine
map applet
Java- applet
code
map.class
<%applet src = “map.class”%> <br> map applet

14. server-plugin (esrimap.dll)
ArcView-IMS: a mixed solution
server-plugin (esrimap.dll)
Java Virtual Machine
arcview map
Java- applet
code
mapcafe. class

15. Internal server (itcnt07 student sites)
Only available within ITC (within “firewall”)
administrator
special dir “www” on personal drive M:
authors
windows network
IIS server itcnt07.itc.nl
Web-browsers
Anonymous access (Web)
http

16. External Web server (eg. Kartoweb)
administrator
Kartoweb server
authors
ftp
username/password privileges
Web-browsers
Anonymous access (Web)
http