Transcript Providing information on the WWW

Web Interfaces and Data
Portals
John Porter
Department of Environmental Sciences
University of Virginia
Roadmap
 Goals
for web data access
 The web interface "tool box"
 Putting the pieces together
 Content management systems
 Exercises
Goals for Ecological Databases
Easy to use – no specialized training
required
 Able to locate/discover data
 Able to produce data in desired forms

» Data files
» Graphs and Maps
» Specialized formats

Users can understand and use data
Circa 1994- The World Wide Web
 Availability
nearly universal
» access rapidly increasing
to use – point and click
 Difficult to update source
documents
 Easy
» Need to edit static text documents
Circa 1994 - Databases
 Difficult
and specialized interfaces
 Powerful capabilities
» Query
» Update
» Output
Suitable for “about 10%” of ecological data
management problems (Gorentz, pers. comm.)
Now!
Web
+
Database
New Power!



ubiquitous
easy to use
easy to query and
update
Examples

An early use, in the Internet Movie
Database (http://www.imdb.com) links
movies with actors and vis versa
» Search for a movie
» Get a list of actors
» Click on actor’s name to get list of movies
they were in
Retrieve customized data via a web
form linked to a database
The Web Portal Toolkit
We have all seen (and used) web pages
that were linked to databases
 But, HOW IS IT DONE?

» Actually there are MANY ways to link
databases and web pages using a wide
variety of tools
Piece #1 Web Forms
<H1>A Simple Form</H1>
<FORM ACTION=“/cgi-bin/test.cgi" METHOD=get >
<H2>Simple input of a string</H2>
<P>Input a sentence:
<INPUT NAME=inputstring SIZE=60> </P>
<INPUT TYPE=SUBMIT>
</FORM>
Tools: Stand-alone Computer
Languages

Visual Basic
» PC’s only

C & C++
» powerful (but with power comes
responsibility)

Pattern Extraction and Regular
expression Language – PERL
» Strong search and parsing capabilities
JAVA – object oriented
 Many more (Python, etc.)

Tools: Computer Languages you
can Insert in a Web Page

Active Server Pages – ASP
» Works primarily with Microsoft products
» Insert Microsoft Visual Basic into web
pages

PHP
» open source
» Works on a wide number of platforms

Specialized languages associated with
specific products (e.g., LITE)
Tools: Languages that Run on
your Browser

Active X
» Microsoft Internet Explorer only

JAVAscript
» Lightweight programs

JAVA
» Full-featured object-oriented programs
Tools: Relational Databases

Commercial Databases
» Oracle
» Microsoft SQL Server

Open Source Databases
» MySQL
» SQLite (lightweight, limited functions)

All provide:
» Structured Query Language (SQL)
» Application Programming Interfaces (APIs) to
interact with computer languages
Putting the Pieces Together

Web forms Interface
» Web authoring tools like DREAMWEAVER
can automate linking web forms to
databases

Computer Programs
» Stored & run on Web Server
» Stored in web page & run on Web Server
» Stored on Web Server & run on Server
» Stored in web page & run on Client

Database
Client-Server Architecture
WWW Server
WWW Server
Software
WWW Client
Internet
WWW Browser
JAVA
HTML
file
HTML
file
HTML
HTMLfile
file
CGI-BIN
Scripts
CGI or SCRIPTS

Apache and others
» If you see /cgi-bin/ in a web address, it is running a
program stored in the cgi-bin directory of the
server
» CGI stands for “Common Gateway Interface”
» it defines the ways to communicate information
between the server and the client

Microsoft IIS
» Uses the “scripts” directory on the server to store
programs
Client-Server Architecture
WWW Server
WWW Server
Software
HTML
file
HTML
file
HTML
HTMLfile
file
WWW Client
Internet
WWW Browser
Basic
configuration for
serving static
documents
Adding a Database
WWW Server
WWW Server
Software
HTML
file
HTML
file
HTML
HTMLfile
file
CGI-BIN
Scripts
WWW Client
Internet
WWW Browser
Database
Database Programs in HTML
Documents

Usually webmasters do NOT allow users to
add programs to the cgi-bin directory
» Dangerous – programs run on the server so only
trusted programs should be in cgi-bin

So, instead a general CGI program (such as
PHP) is used to read specific database
programs that are integrated into a web page
Adding a Database
WWW Server
WWW Server
Software
HTML
file
HTML
file
HTML
HTMLfile
file
CGI-BIN
Scripts
WWW Client
Internet
WWW Browser
Database
Example Program
This example program uses PHP to talk
to a MYSQL relational database
 The details of each step will differ
between databases and languages, but
will share many similarities
 Here we insert information from a web
form into a database and retrieve an
observation number for later use.

/* Connecting, selecting database */
$link = mysql_connect("data.vcrlter.virginia.edu", “myID")
or die("Could not connect");
mysql_select_db("www") or die("Could not select database");
Open
connection
Select
database
/* Performing SQL query */
$query = "insert into waiver
(date_req,station,name,isVert,healthtype)
values('" . date("Y-m-d") . ','$_REQUEST[station]',
‘$_REQUEST[fullname]','Y', $_REQUEST[health])";
Set up
insert
$result = mysql_query($query) or die("Unable to log waiver
creation, Query failed");
Run Insert
Query
$query = "select max(waiver_num) as waiver_num from
waiver";
$result = mysql_query($query) or die("Unable to get waiver
number, Query failed");
extract(mysql_fetch_assoc($result));
mysql_close($link);
Set up query
Run Query
Store result
as PHP
variable
DON’T PANIC!
By now, you may be swamped with new
information, so keep in mind:
» There are good tutorials or books to walk
you through the intricacies of SQL, PHP,
etc.
» Example programs can frequently be
adapted for your use
» Some tools for creating database-enabled
web pages can automate many of the
basic tasks (e.g., Dreamweaver has basic
web form and database interfaces)
Web Portals Made Easy –Content
Management Systems

Content Management Systems (CMS)
» Store ALL the web content in a database (not just
data and metadata)
» Provide pre-written “modules” containing
– Web form-based interfaces
– Associated database programs
» These modules are designed to be easy to use by
even novice webmasters to provide specific
functions on a web page

Examples are PostNuke, SlashDot,
OpenCMS, WIKI
A sample web site developed using POSTNUKE
Administration Page for PostNuke Web Site
Content Management Systems

Advantages
» Easy to configure and use
» Allow input from users (subject to login)
» Many pre-existing modules

Disadvantages
» Existing modules may not meet your needs
» May be difficult to extract content or
transition to other systems
System Requirements for CMS

To use a CMS, you will need
» A Relational Database (e.g., Oracle,
MySQL)
» A computer language (JAVA, PHP etc.)
» A web server

For example, PostNuke, by default,
requires PHP and a MySQL database
Web Services

For some applications your “user” is not
a person, it’s a program on another
computer
» E.g., Provide data to run a model or
graphical package, without human
intervention

Web pages work fine for people, but are
hard for programs to interpret. For this
reason Web Services have developed
Features of Web Services
A Web Service provides the following functions:
 It “advertises” its methods (it tells you what it
can do for you)
 Once you select a method to invoke, the Web
Service does the required processing (often
accessing a database)
 It returns the result as a structured eXtensible
Markup Language (XML) document, suitable
for use with many types of software
Web Services


Web services tools and techniques are still
undergoing rapid development and evolution.
Here are some tools and standards related to
that development:
SOAP – Simple Object Access Protocol
» A “envelope” for packaging requests and receiving
results

WSDL – Web Services Description Language
» A language for describing web services and their
methods
Useful References & Tutorials
PHP – http://www.php.net
 MySQL – http://mysql.com
 HTML Forms, Web Services (SOAP,
WSDL), SQL, XML http://www.w3schools.com/html/
 SQL – http://sqlcourse.com
 Dreamweaver –
http://www.macromedia.com

Exercises
Learn Structured Query Language at:
http://www.sqlcourse.com
 Learn to Administer a real PostNuke
web site at:
http://mareo.org/~jhp7e/ESA04
