Web Engineering Web Engineering

Transcription

News to discuss?
Internet May Be Just A Fad, Says European Body
http://www.newsbytes.com/news/00/158904.html
Web Engineering
Prof. Dr. Dr. h.c. mult. Gerhard Krüger, Albrecht Schmidt
An interim report for the Economic and Social Research Council
(ESRC), says that the development of the Internet over the last
decade may not be the epoch -making event that many have
said....
... The report stems from the results of a two-year investigation
into the use of the Internet, undertaken by the University of
Warwick, which claims that there is already some evidence that
the Net may be a passing fad, as usage among British
teenagers is already starting to fall from its previously high
levels.
Universität Karlsruhe
Fakultät für Informatik
Institut für Telematik
The report speculates that as many as 2 million users of the
Internet in the UK have stopped using it regularly because of
the vast amounts of data online and the need to spend time on
the Web to research that information....
Wintersemester 2000/2001
Prof. Dr. Dr. h.c. mult . Gerhard Krüger, Albrecht Schmidt: Web Engineering, WS00/01
(04-Dez-00)
page 1
page 3
Table of Contents
1. Introduction and History
2. Media and Information
Web Engineering
3. Organizing Information
4. Access to Information and Navigation
Chapter 3: The Web – An Information System
§ Methods for Information Access
§ Hypertext Navigation
§ Access Strategies for the Web
5. Describing and coding Information
page 2
page 4
Methods for Information Access
¨
addressing pages directly
¨
search/browse in catalogs
¨
search for keywords
¨
associative
¨
navigation
Quality of Search Results
¨
recall = the ratio of documents retrieved versus the
number of available documents relevant to the query,
i.e., the fraction returned out of all desirable
documents
¨
precision = the ratio of the number of relevant
documents retrieved versus the total number of
documents retrieved, or the useful fraction of what
was actually retrieved
¨
see information retrieval
page 5
Search / Browse in Catalogs
Addressing Pages Directly
¨
¨
¨
requires unique addresses
¨
§ URL: Uniform Resource Locator
¨
¨
¨
how to get the address?
§ external channel, e.g. TV, radio, press, print, email, etc.
§ guessing the DNS-name, e.g.
www.uni-karlsruhe.de, www.oracle.com, www.linux.org
conventions
¨
address of the catalog must be known
examples
§
§
§
§
§
§
§ E.g. index.html, default.htm , robots.txt
browse predefined classes
search if classes/subclasses are unknown
less directed, open search strategy
if you can not specify what you are looking for ...
How to get listed in a catalog?
§ automatically (submit in a certain category)
§ pages are manually selected, reviews, and added
¨
¨
page 7
page 6
yahoo.com
web.de
lycos.de
netcenter.com
dmoz.org open directory project
and many others ...
page 8
Search for Keywords
¨
Incremental Search
§ refine search results
§ search within results
specific WWW server
§ parts of a search engine
¨
¨
¨
¨
¨
¨
source:
www.altavista.com
www.northernlight.com
§ concept map
§ categorizing results
robot/crawler
indexer
analyzer module
database
retrieval component
recommendation system
§ other user rank content
§ number of links to a page
§ how often is the page
opened when displayed
§ etc ...
page 9
Advanced Search Concepts I
Search using a Query Language
¨
¨
mechanisms to search for keywords
¨
¨
¨
¨
Boolean operators
“fuzzy operators” e.g. NEAR
search for values of certain attributes
examples: www.altavista.com
+domain:com
specify search by
§
§
§
§
§
§
§
§
§ keyword matching
§ query language
+Netscape
page 11
search term
term exclusion
date
top level domain
domain
hostname
language
country
§ matching (exact, fuzzy)
§ search term in:
¨
¨
¨
¨
title
body
domain
link
+ url:Java +applet:*
+host:www.ibm.com
+image:sharon *
+confidential
+title:stone
link:www.teco .uni- karlsruhe.de
(image:bill NEAR clinton ) OR
(image:clinton NEAR bill) OR
title:"Bill Clinton"
source:
www.google.com
page 10
page 12
Advanced Search Concepts II
¨
Multimedia Search
searching for similar pages
¨
¨
¨
§ images
§ video
§ audio
searching for pages that link to a page
searching within a certain domain
à specialized search engines
¨
¨
¨
cached pages – no 404
source:
www.google.com
content
based on
text/keywords
next to content
e.g.
§
§
§
§
page 13
Natural Language Search
¨
www.altavista.com
www.ditto.com
music.lycos.com
multimedia.lycos.com
page 15
Associative
query a search engine in „plain“ English
¨
semantic links in hypertext
§ links in text (related content)
§ icons and images
§ maps
¨
different types of links
¨
different semantics
source:
www.askjeeves.com
page 14
page 16
Search Functionality
¨
¨
¨
Hypertext – Navigational Patterns
providing a search function to visitors of a specific site
(company web site, university site)
when a users is on the site you want to help him to find
what he/she is looking for
two approaches
§ search engine or directory
for the specific site
¨
¨
customized interface
detailed inclusion
and exclusion rules
¨
¨
¨
navigational structure within the content
e.g. www.useit.com
e.g.: www.sun.com
e.g.: www.amazon.de
z.B.: www.iflyswa .com, www.hagebau.de
http://www8.org/w8-papers/5b- hypertext-media/improving/improving.html
page 17
Hypertext - Navigation
links beyond content and semantic
¨
§ landmark
„Provide direct access to critical sub -systems in the Web
Information System“
§ set-based navigation
„Organize the information in Sets of related information items.
Provide intra-set navigation capabilities.“
§ often combined landmark & set-based navigation
§ metaphorical navigation
also useful instead
of a missing page
¨
§ text based
¨
embedded in
the site
Navigational Design Patterns [Rossi et al. 98]
¨
§ using a „public“ search engine
with attributes to restrict the
search to this site
¨
¨
page 19
Text Based Navigation
§ up, down, next, ...
§ often based on icon
§ author builds/defines this structure
¨
tools for navigation
§ history, back/forward, home
§ bookmarks
§ in the user interface of the web client
¨
navigational patterns
Source: http://www.useit.com
page 18
page 20
Landmark & Set-based Navigation I
Source: http://www.amazon.de
page 21
Landmark & Set-based Navigation II
Source: http://www.wapforum.org
page 22
Metaphorical Navigation I
Source, 1998: http://www.iflyswa.com
page 23
Metaphorical Navigation II
Source: http://www.hagebau.de
page 24
Table of Contents
Markup
¨
roots: computerized typesetting
1. Introduction and History
§ typesetting macros embedded in ASCII
2. Media and Information
§ presentational markup
¨
¨
3. Organizing Information
¨
layout directives, e.g. TEX
commands to define the layout
semantic markup
4. Access to Information and Navigation
§ authors put annotations into their texts to help the publisher to
understand what type of text this is (e.g. „this is a heading“)
§ annotations are agreed between author and publisher
5. Describing and coding Information
§ publisher decides on the layout
§ descriptive markup
§
§
§
§
Markup
SGML
XML
HTML
¨
describing content not the layout
§ markup to support search in documents
¨
¨
Coding Documents
\twocolumn[
\begin{center}\Large { A Modular Neural
Network Architecture with Additional
Generalization Abilities for High
Dimensional Input Vectors}
tex
\end{center}
page 25
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<td><font face="Arial, Helvetica">
<P> In 1995/1996 I did an MSc inHTML
computing at the <A
HREF="http://www.mmu.ac.uk">Manchester
Metropolitan University</A> in the
<A HREF="http://www.doc.mmu.ac.uk">
Department of Computing</A>. Studying
in <A REF="http://www.manchester.com/">
words in headings are more important than in footnotes
markup for machines vs. markup for humans
page 26
page 27
Markup - ISO-Definitions
¨
markup
§ text that is added to the data of a document in order to
convey information about it
¨
descriptive markup
§ markup that describes the structure and other attributes of a
document in a non-system-specific way, independently of
any processing that may be performed on it
¨
processing instruction (PI)
§ markup consisting of system -specific data that controls how
a document is to be processed
page 28
Descriptive Markup versus
Processing Instruction
¨
Editorial Structure II
¨
descriptive markup
§ editorial structure
§ content structure
¨
¨
processing instructions
§ layout
¨
descriptive markup
§ layout
¨
Example
Announcement
In the course Web Engineering
Albrecht Schmidt will talk about ...
Example
<main-title>Announcement</main-title>
<paragraph>In the course Web Engineering
Albrecht Schmidt will talk about ... </paragraph>
page 29
Editorial Structure
¨
Content Structure I
¨
descriptive markup
¨
¨
Example
In the course Web Engineering
Albrecht Schmidt will talk about ...
§ layout
§ layout
¨
descriptive markup
¨
page 31
page 30
Example
<paragraph>In the course <course>Web Engineering
</course> Albrecht Schmidt will talk about ...
</paragraph>
page 32
Layout II
Content Structure II
¨
¨
descriptive markup
¨
¨
¨
Example
<paragraph>In the course <course>Web Engineering
</course> <name>Albrecht Schmidt</name> will talk
about ... </paragraph>
processinginstructions
§ layout
§ layout
¨
descriptive markup
Example
<head columns=1>
<main-title><bold>Announcement</bold></main-title>
</head>
<content columns=2>
<paragraph>In the course <course>Web Engineering </course>
<name><italic>Albrecht Schmidt </italic> </name>
will talk about ... </paragraph>
</content>
page 33
Layout I
¨
Generic vs. Specific Markup
¨
descriptive markup
processinginstructions
¨
§ layout
¨
Example
<head columns=1>
</head>
<content columns=2>
<paragraph>In the course <course>Web Engineering </course>
<name>Albrecht Schmidt</name> will talk about ... </paragraph>
</content>
layout structure
§ specific <italic>Web Engineering</ italic >
§ generic <emphasis>Web Engineering</emphasis >
¨
page 35
page 34
content structure
§ specific
§ generic
¨
<course-title>Web Engineering</course-title >
<keyword>Web Engineering</keyword>
publication structure
§ specific <verse> ... </verse>
§ generic <paragraph> ... </paragraph>
page 36
SGML
¨
Standard Generalized Markup Language
§ ISO-Standard [ISO/IS 8879, 1986]
§ developed from GML, IBM 1969 (Goldfarb, Mosher, Lorie)
§ distinction between content and presentation
¨
dilemma of specific markup language:
§ What is an appropriate set of tags?
¨
generalized markup
§ documents are desribed in three parts
¨
¨
¨
SGML declaration:
mapping of the abstract SGML Syntax onto concrete characters
definition of STAGO e.g. '<' or TAGC e.g. '>' or charset
Document Type Definition, DTD:
definition of tags and their meaning
the document (content) in the markup define in the DTD
§ semantic of markup is context dependent
page 37

Web Engineering Web Engineering

Transcription

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