Information Systems Analysis and Design CSC340 XXII Website Design The Web Hypertext Data Independence Data Models for Hypertext Documents The Araneus Data Model ADM The Navigational Conceptual Model NCM The Araneus Methodology for Website Design 2001 Paolo Atzeni Web Design 1 Information Systems Analysis and Design CSC340 The Web The spread of World Wide Web hereafter Web technology is one of the most remarkable phenomena of the last few years in all areas of computing and communication The Web e g Web browsers is becoming a standard interface for the general public to access and exchange information The protocol is very simple and public The interface is uniform The content is extremely rich both in breadth and in depth Moreover the Web is becoming a standard interface for accessing many specialized services specifically information systems and databases of every type 2001 Paolo Atzeni Web Design 2 Information Systems Analysis and Design CSC340 Web Features and Open Problems The Web is a simple and powerful data integration tool Two basic approaches to Web based data integration Coarse grain pages of hypertext Fine grain unified interface for accessing different usually similar information systems available on the Web The Web is built out of semi structured HTML XML documents databases contain structured I e tuple record data Databases can be queried in a flexible way hypertext documents are easy to access but cannot be queried Web sites are often difficult to explore use and monitor Web sites are also difficult to design and maintain 2001 Paolo Atzeni Web Design 3 Information Systems Analysis and Design CSC340 Problems with Large Websites Information is often poorly organized and difficult to access It is often unclear what information is available on a given website The access structure of many websites is casual and idiosyncratic causing frequent dangling references The style of presentation is often heterogeneous Large websites are usually difficult to update or change their structure It is also difficult to change the presentation structure and or details 2001 Paolo Atzeni Web Design 4 Information Systems Analysis and Design CSC340 Data Independence for Hypertext Documents You might say that there are three facets to the Web Data what information is offered through the site and what are the conceptual details and the logical organization Hypertext how data is arranged in pages and what navigation links correlate them Presentation the appearance of each piece of information on each pages As much as possible we d like to decouple the three so that changes to one affect minimally the other two facets of the Web 2001 Paolo Atzeni Web Design 5 Information Systems Analysis and Design CSC340 An Example 2001 Paolo Atzeni Web Design 6 Information Systems Analysis and Design CSC340 Another 2001 Paolo Atzeni Web Design 7 Information Systems Analysis and Design CSC340 and Another 2001 Paolo Atzeni Web Design 8 Information Systems Analysis and Design CSC340 Design Issues Data choose the content Hypertext choose navigation paths Presentation define layout and graphics Maintenance Issues Data changing the content Hypertext changing navigation paths Presentation changing layout and graphics Components and Models Data Hypertext Presentation 2001 Paolo Atzeni ER and Relational HTML What is missing is a model for hypertexts Web Design 9 Information Systems Analysis and Design CSC340 Models for Hypertext Documents In data intensive Websites and often in general there are many pages with a similar or even the same structure Forty years ago people realized that in an application it is often the case that there are many records with the same structure files and file technology were invented to exploit this fact Likewise the notion of a schema for a database was later introduced as an overall description of the content of a database We need something similar for the Web 2001 Paolo Atzeni Web Design 10 Information Systems Analysis and Design CSC340 A Web Page 2001 Paolo Atzeni Web Design 11 Information Systems Analysis and Design CSC340 A Page Schema ProfessorPage ProfessorPage Name Position Address EMail ResearchList Area ToResP 2001 Paolo Atzeni Text elements List element Web Design 12 Information Systems Analysis and Design CSC340 ADM Araneus Data Model A Logical Model for Hypertext Documents Developed at the University of Rome III Universita di Roma Tre by Paolo Atzeni Paolo Merialdo Giansalvatore Mecca and colleagues Its features include Page schemas Simple attributes text images link anchor URL Complex attributes such as lists possibly nested A heterogeneous union operation Forms as virtual lists over form fields and links to a result 2001 Paolo Atzeni Web Design 13 Information Systems Analysis and Design CSC340 Another Web Page Containing a List of Links 2001 Paolo Atzeni Web Design 14 Information Systems Analysis and Design CSC340 A Page Schema for ProfessorListPage ProfessorListPage ProfessorList Name ToProfP 2001 Paolo Atzeni Web Design 15 Information Systems Analysis and Design CSC340 An ADM Schema ProfessorListPage ProfessorList Name ToProfP 2001 Paolo Atzeni ProfessorPage Name Position Address EMail ResearchList Area ToResP Web Design 16 Information Systems Analysis and Design CSC340 Heterogeneous Union and Forms 2001 Paolo Atzeni Web Design 17 Information Systems Analysis and Design CSC340 Heterogeneous Union and Forms Form element SearchProfPage Name Submit ProfessorListPage ProfessorList Name ToProfP ProfessorPage U Name Position Address EMail ResearchList Area ToResP 2001 Paolo Atzeni Web Design 18 Information Systems Analysis and Design CSC340 Data Models Again Database Conceptual Schema entities relationships ER Hypertext Logical Schema page schemas links ADM There is considerable conceptual distance between the two 2001 Paolo Atzeni Web Design 19 Information Systems Analysis and Design CSC340 A Simple ER Schema 2001 Paolo Atzeni Web Design 20 Information Systems Analysis and Design CSC340 An ADM Schema 2001 Paolo Atzeni Web Design 21 Information Systems Analysis and Design CSC340 The Navigational Conceptual Model NCM ER NCM ADM Database Conceptual Schema entities relationships Hypertext Conceptual Schema macroentities directed relationships aggregations Hypertext Logical Schema page schemas links NCM fills the gap between the two 2001 Paolo Atzeni Web Design 22 Information Systems Analysis and Design CSC340 Macroentities and Directed Relationships Name Name Professor Room
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