Audio – Reception, Play-back � large amount of data � 1 Minute ~ 10MB raw (44,1kHz * 2 Byte * 60 s * 2) Web Engineering (frequency * bit-depth * time * channels) � long download times Prof. Dr. Dr. h.c. mult. Gerhard Krüger, Albrecht Schmidt � optimizing the file size � length of the audio clip � number of channels Universität Karlsruhe � bit-depth Fakultät für Informatik � sampling rate Institut für Telematik � Play-back during reception, buffering Wintersemester 1999/2000 � Streaming Formats � Alternative formats, e.g. RealAudio, Quicktime Audio Prof. Dr. Dr. h.c. mult. Gerhard Krüger, Albrecht Schmidt: Web Engineering, WS00/01 page 1 Prof. Dr. Dr. h.c. mult. Gerhard Krüger, Albrecht Schmidt: Web Engineering, WS00/01 page 3 Streaming, e.g. RealAudio � link: <A HREF="musik.ram"> here you get live music!</a> � SMIL – selection of bandwidth Synchronized Multimedia Integration Language Web Engineering � meta file: musik.ram pnm://129.13.170.22/live/musik.ra � data transmission � UDP � back-channel, scalability Chapter 3: The Web – An Information System <smil> <body> <switch> <ref src=“myclipcm.rm” system-bitrate=”220000”/> <ref src=“myclip56.rm” system-bitrate=”32000”/> <ref src=“myclip28.rm” system-bitrate=”20000”/> </switch> </body> </smil > Prof. Dr. Dr. h.c. mult. Gerhard Krüger, Albrecht Schmidt: Web Engineering, WS00/01 page 2 Prof. Dr. Dr. h.c. mult. Gerhard Krüger, Albrecht Schmidt: Web Engineering, WS00/01 page 4
Table of Contents Collections 1. Introduction and History � set (without order) 2. Media and Information � classification based on criteria defined implicitly by the collector 3. Organizing Information � Systems and Classifications � Structuring Information � motivation � Hypertext � Complete or representative acquisition within a limited � Organizing Information in the WWW domain 4. Access to Information and Navigation 5. Describing and coding Information Prof. Dr. Dr. h.c. mult. Gerhard Krüger, Albrecht Schmidt: Web Engineering, WS00/01 page 5 Prof. Dr. Dr. h.c. mult. Gerhard Krüger, Albrecht Schmidt: Web Engineering, WS00/01 page 7 Systematic Approaches Index, Catalog � Indexed information � Collect and Summarize � Collection � explicit classification based on categories or according to to keywords � Indexing � Catalog � motivation � Library � classification of information across different domains � Connections based on Content � examples � Hypertext � Encyclopedia � The Library of Congress Classification System http://lcweb.loc.gov/catdir/cpso/lcco/lcco.html � The ACM Computing Classification System http://www.acm.org/class/1998/ Prof. Dr. Dr. h.c. mult. Gerhard Krüger, Albrecht Schmidt: Web Engineering, WS00/01 page 6 Prof. Dr. Dr. h.c. mult. Gerhard Krüger, Albrecht Schmidt: Web Engineering, WS00/01 page 8
LIBRARY OF CONGRESS Structuring Information CLASSIFICATION OUTLINE � linear A -- GENERAL WORKS L -- EDUCATION B -- PHILOSOPHY. M -- MUSIC AND BOOKS ON PSYCHOLOGY. RELIGION MUSIC � hierarchical C -- AUXILIARY SCIENCES OF N -- FINE ARTS HISTORY P -- LANGUAGE AND � grid D -- HISTORY: GENERAL AND LITERATURE OLD WORLD Q -- SCIENCE E -- HISTORY: AMERICA R -- MEDICINE � graph / web F -- HISTORY: AMERICA S -- AGRICULTURE G -- GEOGRAPHY. T -- TECHNOLOGY ANTHROPOLOGY. U -- MILITARY SCIENCE RECREATION V -- NAVAL SCIENCE H -- SOCIAL SCIENCES Z -- LIBRARY SCIENCE J -- POLITICAL SCIENCE K -- LAW Prof. Dr. Dr. h.c. mult. Gerhard Krüger, Albrecht Schmidt: Web Engineering, WS00/01 page 9 Prof. Dr. Dr. h.c. mult. Gerhard Krüger, Albrecht Schmidt: Web Engineering, WS00/01 page 11 Connections based on Content Linear Structures I � using links/relations between the content of � pure linear information chunks � direct association instead of indirect association according to a classification � strict guidance � „like humans organize there knowledge“ � little choices for the user � pre-caching possible Prof. Dr. Dr. h.c. mult. Gerhard Krüger, Albrecht Schmidt: Web Engineering, WS00/01 page 10 Prof. Dr. Dr. h.c. mult. Gerhard Krüger, Albrecht Schmidt: Web Engineering, WS00/01 page 12
Linear Structures II Linear Structures IV � linear with options � linear with side branches � guidance � some choices for the user active interaction � additional information on side path � different levels of detail � guidance on main path � scenarios: different level of expertise, profiles Prof. Dr. Dr. h.c. mult. Gerhard Krüger, Albrecht Schmidt: Web Engineering, WS00/01 page 13 Prof. Dr. Dr. h.c. mult. Gerhard Krüger, Albrecht Schmidt: Web Engineering, WS00/01 page 15 Linear Structures III Circular Structure � closed guided path � linear with alternatives � Variants / side paths � entry � guidance � some choices for the user � E.g. Web Rings active interaction http://dir.webring.yahoo.com � scenarios: questionnaires Prof. Dr. Dr. h.c. mult. Gerhard Krüger, Albrecht Schmidt: Web Engineering, WS00/01 page 14 Prof. Dr. Dr. h.c. mult. Gerhard Krüger, Albrecht Schmidt: Web Engineering, WS00/01 page 16
Information Grid Hierarchical Information Structure � deep hierarchy � flat hierarchy � ordered on two � Lookup table (A-Z) orthogonal criteria � more the 6-10 is questionable (cognitive psychology) � user get a „feeling of space“ � e.g. product catalog Prof. Dr. Dr. h.c. mult. Gerhard Krüger, Albrecht Schmidt: Web Engineering, WS00/01 page 17 Prof. Dr. Dr. h.c. mult. Gerhard Krüger, Albrecht Schmidt: Web Engineering, WS00/01 page 19 Example Linked Information Structures Grid Information Structure � pure webs � catalog M4 M6 M8 screws nut M4 M6 M8 � difficult for orientation discs 4mm 6mm 8mm � extremely expressive Prof. Dr. Dr. h.c. mult. Gerhard Krüger, Albrecht Schmidt: Web Engineering, WS00/01 page 18 Prof. Dr. Dr. h.c. mult. Gerhard Krüger, Albrecht Schmidt: Web Engineering, WS00/01 page 20
Information Mapping Hypertext � information mapping � components � mapping of information onto an abstract structure � mapping the structure to web pages � classification � Trade Offs � reference model � expressive vs. pre-defined structure � guidance vs. confusion � practical design expressiveness pure web grid hierarchy linear fixed structure guidance no guidance Prof. Dr. Dr. h.c. mult. Gerhard Krüger, Albrecht Schmidt: Web Engineering, WS00/01 page 21 Prof. Dr. Dr. h.c. mult. Gerhard Krüger, Albrecht Schmidt: Web Engineering, WS00/01 page 23 Organizing Information in the WWW Hypertext � based on a open hypertext system � concept to organize information � motivation � information can be organized in any way � “knowledge” is not linear, it is associative � partly „real“ hypertext with links based on content � authoring a document = � partly indexed documents and catalogs making knowledge linear � Partly simple collections of resources � reading a document = reproduce the non-linear structure of the knowledge � navigation � information is structured very differently � often mixture of linear and hierarchy � hypertext links are often not associative, but just to build a Authoring Reading linear hierarchical navigation structure � previous/next � hypertext-documents: � up/down/home � keep the inherent association of information in a document Prof. Dr. Dr. h.c. mult. Gerhard Krüger, Albrecht Schmidt: Web Engineering, WS00/01 page 22 Prof. Dr. Dr. h.c. mult. Gerhard Krüger, Albrecht Schmidt: Web Engineering, WS00/01 page 24
Roots of Hypertext Hypertext Components � “Memex” � structure � Vannevar Bush: “As we may think”, 1945 � hypertext document: directed graph � “Memory Expander”-Machine � associative storage/access � components � personal annotation linked to documents � node: information unit � anchor: Information chunk within a node, � Xanadu target for a link � Ted Nelson, 1965/1981 � link: connections between nodes � term Hypertext � Docuverse: global hypertext system, Pay per View anchor � Augment/NLS (oNLine System) link � Douglas Englebart, 1968 � Shared Hypertext Document Spaces Prof. Dr. Dr. h.c. mult. Gerhard Krüger, Albrecht Schmidt: Web Engineering, WS00/01 page 25 Prof. Dr. Dr. h.c. mult. Gerhard Krüger, Albrecht Schmidt: Web Engineering, WS00/01 page 28 Hypertext – Example I Node � single media nodes � only one media type per node � mixed media nodes � different media types possible per node � alternatives, combination � systems with limited content size � no internal navigation � e.g. HyperCard � systems with unlimited content size � internal navigation necessary � e.g. Scrolling Prof. Dr. Dr. h.c. mult. Gerhard Krüger, Albrecht Schmidt: Web Engineering, WS00/01 page 26 Prof. Dr. Dr. h.c. mult. Gerhard Krüger, Albrecht Schmidt: Web Engineering, WS00/01 page 29
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