Transcript kin260_lec10

Email & Web Searches
Kin 260
Jackie Kiwata
Overview

Email
– Message Transfer Agents
– User Agents
– Envelope & Contents

Web Searches
– Search Engines
– Key Words
– Operators
– CSLA Library Research
Electronic Mail

Use of email by general public exploded in
the 1990s
 Prior to 90’s, used mostly in academia

Email systems composed of 2 subsystems
– User Agents
– Message Transfer Agents

Key idea behind email system: envelope
and contents
– Separate routing information from message
Message Transfer Agents
Move messages from source to destination
 Use daemons

– Computer Science definition: processes that
run in the background
– NOT:
Daemons

Purpose:
– Establish connection to destination
– Reliably transfer message
– Close connection
– Perform steps automatically without bothering
user
Daemon Example
from <[email protected]>
to
[email protected],
date Nov 8, 2007 1:42 PM
Subject: Delivery Status Notification (Failure)
This is an automatically generated Delivery Status
Notification
Delivery to the following recipient failed permanently:
[email protected]
Technical details of permanent failure:
PERM_FAILURE: SMTP Error (state 13): 550
<[email protected]> recipient rejected
User Agents
Normally a program
 Accepts a variety of commands, including:

– Composing messages
– Receiving messages
– Replying to messages
– Manipulating mailboxes

e.g. Outlook, Gmail, Hotmail
Email - Envelope

Read by Message Transfer Agents
– Not seen by person reading email
Encapsulates the message
 Similar to paper envelopes transported by the
post office
 Contains all the information needed to transport
the message

– Destination Address
– Priority
– Security Level
Email - Content

Content consists of two parts
1.
Header
-
2.
contains information for User Agents
Body
- Contains the message read by the human
recipient
Anatomy of an Email message
Header
Return-Path: <[email protected]>
Received: from roche.bath.ucla.edu ([138.38.32.21]
ident=yalrla9a1j69szla2ydr) by serena.bath.smtp.gmail
with esmtp; Sat, 07 Jun 2007 20:17:35 +0100
Date: Sat, 7 Jun 2001 12:35:58 -0700
From: Jane Martin<[email protected]>
To: Bob Richards <[email protected]>
Subject: Athletic Director Position
Message-ID:
<[email protected]>
User-Agent: Mutt/1.2.5.1i
Body
Dear Mr. Richards:
Please find my resume attached.
Sincerely,
Jane Martin
Transfer Protocols
How User Agents talk to Message Transfer
Agents
 Daemons will speak one of the following
protocols:

– SMTP: Simple Mail Transfer Protocol
– POP3: Post Office Protocol 3
– IMAP: Internet Message Access Protocol

e.g. Gmail uses POP3 to receive mail and
SMTP to send mail
Web Searches
Web is a terrific place to obtain info on
any topic
 But all too often, waste time on reviewing
useless web site results
 There has to be a better way!

Making Searches Better
1. Use a sophisticated search engine
i.e. Google
2. Choose key words wisely
i.e. “Exercise Science programs” instead
of “Exercise”
3. Refine search query with Operators
i.e. +, -, “”
Web Search Engines



Provide an interface to search for pages,
images or other types of web files
Use algorithms
Work by:
1. Web crawling
2. Indexing
3. Searching
Web Crawling

Accomplished using web crawlers, or
spiders
– Automated programs that browse pages on
the WWW

Crawlers create a copy of visited pages for
use in later analysis
Indexing

Contents of stored pages are analyzed
– Words extracted from titles, headings, and
special fields called meta tags
Data about web pages are stored in an
index database
 When a user enters a search query, search
engine checks the index database

Searching & Results
Search engine returns results based on
search query
 Search engine will rank the results and
show most relevant higher in the list

– Most relevant = how closely key words match
on web page
– Issue: In 2006, spammers created websites
containing random sequences of high-traffic
keywords. Results were polluted with pages
that contained little or no relevance.
Choosing Key Words
Key to finding information quickly
 Get better results if use multiple search
terms that are specific
 E.g. “Sports” vs. “Sports medicine
programs in California”
 Note: Google will ignore capitalization and
common words like “and”, “or”, “how”

Basic Operators
Quotes “”
1.
- Will search for pages with exact phrase
- Good if know title of article
- E.g. “Expression of the bilateral deficit”
Positive Terms +
2.
-
-
If put + before a word, search engine must
return results that include the word
Use if search is omitting common words
essential to results
E.g. Star Wars Episode +1
Basic Operators, con’t.
3. Negative Terms –
- If put – before a word, search engine will
omit results containing word
- Use if search term has more than one
meaning
-e.g. vo2max test -cycle
-e.g. rehab -winehouse
Advanced Operators
1.
2.
3.
-
OR search
Find results that include either of 2 search
terms
e.g. vo2max test cycle OR treadmill
Domain search
Find results on one specific website
E.g. biomechanics site:www.usc.edu
Fill in the blanks search *
Ask Google to fill in the blank for you
Add an * at the part you want filled in
e.g. glycolysis discovered by *
Helpful Specialized Search Sites

CSLA Library
– http://www.calstatela.edu/library/

Google Scholar
– http://scholar.google.com
– Searches research publications, books

Google Image search
– http://images.google.com
– Only returns results that contain images
Practical Ex. – CSLA Library Search
Usually, will use Article search
Then can choose
database by Subject
(i.e. Kinesiology)
Or choose database
directly by name (i.e.
Medline)
Helpful Hints

Can access CSLA library databases from home
–
–

Must have NIS account
If use ERIC, can only access abstracts, not full text
Most efficient to least efficient searching terms:
1.
2.
3.
4.
5.
Title
Keyword
Author
Abstract
All text
Ex – Medline Search
You want to find studies on caffeine
supplementation during high-intensity
exercise bouts of varying duration on a
cycle ergometer.
 Use the MEDLINE database through the
CSULA library
 Must find the full text version (html or
pdf).

Extra Credit
In preparation for next lecture, do the
following:
1. Sign up for gmail (free)
2. Email me from your gmail account
3. Do this by 5:00 pm on Friday and I will
add 1 extra point to your overall lab
score
 If you already have a gmail account, just
do steps 2-3.
References
Google Search Guide
http://www.google.com/intl/en/help/basics.html
 Wiki Search Engine page

http://en.wikipedia.org/wiki/Web_search_engine
Email
Tanenbaum, A. S. (2003). Computer Networks.
Upper Saddle River, NJ: Prentice Hall
