Web Information Systems. Sistemi Informativi Aziendali A.A. 2012/2013

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1 Web Information Systems

2 Sommario 1. Definizione 2. Ambiti applicativi 3. Architetture di riferimento 2

3 Definizione Web Information Systems

4 Definizione Web Information System (WIS) La comunicazione tra macchine e utenti avviene sulla rete Internet pubblica o su una rete privata basata sugli standard Internet (VPN) L accesso alle informazioni e ai servizi è supportato da programmi per la gestione dell interfaccia utente noti come browser. Cap. 3 Pag. 93 4

5 Attori Company Company Public service User User 5

6 Modelli di collaborazione B2B (business to business ): collaboration among companies B2C (business to consumer ): on-line shops C2C (consumer to consumer ): auctions, buy-sell notices Government to business : on-line taxes, services to companies Government to citizens : on-line taxes 6

7 Ambiti applicativi Web Information Systems

8 Esempi On-line shops of consumer goods On-line auctions Thematic portal (links, user community, latest news) Distribution of components or raw materials Services (bank, finance, insurance, travel, consultancy, ) Publications (newspapers, encyclopedias, press agencies, ) 8

9 Complessità organizzativa e di sistema Una possibile classificazione Negoziazione automatica Integrazione catena del valore - marketspace Monitoraggio workflow evoluti e condivisi CRM - SCM Aste on-line Siti e portali standard B2C Tipo di relazione B2B p

10 Livelli di complessità Siti informativi Chi siamo / Prodotti / Servizi / Contatti Newsletter, Giornale, Blog, Siti dispositivi Scelta prodotto, configurazione, acquisto Sistemi gestionali CRM, SCM, ERP, MRP, Sistemi autonomi Negoziazione, transazione, monitoraggio Portali, marketplace, marketspace Aggregazione di più aziende/prodotti correlati 10

11 Architetture di riferimento Web Information Systems

12 Evoluzione delle architetture web 12 Architetture Web Percorso 7

13 Architettura ad N livelli Browser Internet infrastructure Web Server Application Server Database Server Client Ciascun livello ha un ruolo ben definito Uno o più server implementano ciascun livello I server possono condividere lo stesso hardware La comunicazione tra i livelli avviene attraverso meccanismi di rete 3 rd party services 13 Architetture Web Percorso 7

14 Architettura generale Internet Server(s) Client Storicamente, un browser web Ma anche: Applicazione Mobile Applicazione Desktop Altra applicazione server 14 Architetture Web Percorso 7

15 General Architecture 15

16 Components One or more connections to the Internet by means of an Internet Service Provider (ISP). One or more servers implementing each tier/level of the architecture. One or more physical networks for interconnecting the servers. One or more network devices (router, firewall, switch) which implement communication and security policies. 16

17 Definition Server may be defined as: Logical definition: A process that runs on a host that relays information to a client upon the client sending it a request. Physical definition: A host computer on a network that holds information (eg, Web sites) and responds to requests for information 17

18 Web server Manages the HTTP protocol (handles requests and provides responses) Receives client requests Reads static pages from the filesystem Activates the application server for dynamic pages (server-side) Provides an HTML file back to the client One HTTP connection for each request Multi-process, Multi-threaded or Process pool 18

19 Example Internet Web server HTML files Client URL http request path display page http response send HTML browser TCP/IP server file system 19

20 Adopted standards URL (uniform resource locator) for finding web pages HTML (hyper text markup language) for writing web pages GIF (graphics interchange format) for images HTTP (hyper text transfer protocol) for client-server interaction TCP/IP (transmission control protocol over internet protocol) for data transfer 20

21 URL RFC DNS URI Rewriting TCP /home/corno/public_html/index.html File system Contact server HTML file contents 21

22 URI Basics Scheme Hostname Query Scheme Hostname Query Scheme Userinfo Hostname Port Scheme Hostname Query Fragment Architetture Web Percorso 7 22

23 HTTP protocol RFC 2616, RFC GET /~corno/index.html HTTP/1.0 Accept: text/html Accept: image/gif User-Agent: CornoSoft SuperBrowser 9.45 HTTP/ OK Date: Monday, 01-Jan :00:00 GMT Server: Apache MIME-Version: 1.0 Last-Modified: 31-Dec-2000 Content-type: text/html Content-lemgth: 3021 <HTML>... 23

24 Performance measures Latency: time required for providing a 0 byte http page. Includes the server activation time, the request decoding time, the file access time, the transmission time and the time for closing the connection. Unit of measure: http/s or s/http Throughput: maximum speed at which infinite-sized pages can be sent. Unit of measure: Bytes (Mbytes)/s #Requests / s 24

25 Delay time T = Latency + ByteHTML / Throughput This equation is valid if: The other architecture elements (I/O subsystem, network,...) are not overloaded The web server has not yet reached its maximum workload Example: Latency: 0,1s ByteHTML: 100kBytes Throughput: 800kBytes/s T= 0,1s+ 100KBytes / 800KBytes/s =0,225s 25

26 Static web transaction Browser Web server t 0 t 1 t 2 t 3 t 6 t 7 t 8 t 9 t 0 t 1 Disk access t 4 t 5 26 server response time network transfer time total response time user think time

27 Architettura generale del web Server web (Apache, IIS) HTM File HTML Schermo Browser Mouse/ Tastiera i n t e r n e t File Immagini IMG Applicazione web (ASP, PHP, JSP, ) Motore Layout IMG HTM 27

28 The most adopted web servers Source: Architetture Web Percorso 7 28

29 Application server Dynamic page generation Manages the site business logic It's the middle tier between the client browser and the data residing on a database Implements the session mechanisms Different technologies and architectures are available 29

30 Dynamic web transaction Internet Web server Application Client URL display page http request & POST data http response command send parameters HTML logic browser TCP/IP server application 30

31 Adopted standards HTTP-POST for sending user-specified data CGI (common gateway interface), ISAPI (internet information server application programming interface), server-side script, java servlet for integrating application logic into web servers ASP (active server pages), PHP, PERL as new languages for application development 31

32 URL (HTTP GET) Application Parameters CPU Disk Libraries HTML 32

33 Dynamic web transaction Browser Web server t 0 t 1 t 2 t 3 t 6 t 7 t 8 t 9 t 0 t 1 Application server t 4 t 5 33 application time total server time total response time

34 Database server Stores the data on which the application server works. Executes the queries issued by the application server: Updates the stored data Inserts new data Provides back query results The most frequent/complex queries can be implemented internally as stored procedures (pre-compiled queries with parameters) 34

35 Example Internet Web server Application Database Client URL http & POST command parameters query display page http send HTML data browser TCP/IP server application database 35

36 Adopted standards Cookies for storing the state of a session Java, JavaScript, ActiveX, Flash to program the user interface on the browser SQL (structured query language), ODBC (open database connectivity) to access data bases 36

37 Database server Queries are almost always in SQL SELECT * FROM table;... Often adopts the relational database model Other models can be used Object model Triple model The most advanced/complete solutions are called Transaction servers 37

38 Database-driven transaction Browser Web server Application server Database server 38 t 1 t 8 t 0 t 9 t 3 t 6 t 2 t 7 t 4 t 5 application time database time total server time total response time t 0 t 1

39 Example (PHP) The application composes the query <?php $query = SELECT doc_id FROM key_doc_index, keywords WHERE key_doc_index.key_id = keywords.id AND keywords.key = $_REQUEST[ query ]; ; The query is sent to the db-server and a rowset containing the results is returned $rowset = mysql_query($query); { while($row = mysql_fetch_row($rowset)) //elaborate data }?> The application elaborates the data 39

40 Architettura generale del web Server web (Apache, IIS) HTM File HTML Schermo Motore Layout Browser Mouse/ Tastiera i n t e r n e t File Immagini IMG Applicazione web (ASP, PHP, JSP, ) SQL Server database DBMS IMG HTM Data base 40

41 Architettura generale del web Server web (Apache, IIS) HTM File HTML IMG Schermo Motore Layout CSS Browser DOM HTM Mouse/ Tastiera Motore Javascript HTM JS i n t e r n e t File Immagini IMG Fogli di stile CSS CSS Javascript JS Applicazione web (ASP, PHP, JSP, ) SQL Server database DBMS Data base 41

42 Web 2.0 Web applications support social interaction models Peer exchange and user-contributed content instead of rigid publisher/reader pattern Online communities Rich, dynamic, interactive user interfaces Integration of contents across web sites (mashups) 42

43 Rich-Client Asynchronous Transactions Internet Web server Application Database Client-side Application Client http URL DOM display page events runtime browser 43 XML/JSON http & POST http TCP/IP command send server application database parameters HTML query data

44 Adopted standards Dynamic HTML: DOM, Javascript, CSS JavaScript, Flash to handle a runtime environment on the browser DOM (XHTML Document Object Model) to allow on-the fly modification of the web page CSS 2.1 to modify attribute and handle objects AJAX: Asynchronous Javascript and XML XMLHttpRequest for asynchronous communication to the server Data transfer formats: JSON, XML, RDF, RSS, Atom, FOAF,... Mash-up technology 44

45 Rich-client transaction Browser t 0 t 1 t 8 t 9 t 0 t 1 Runtime Web server t 2 t 3 t 6 t 7 Application server t 4 t 5 Database server 45

46 Architettura generale del web Server web (Apache, IIS) Dati XML, JSON HTM File HTML IMG Schermo Motore Layout CSS Browser DOM HTM Mouse/ Tastiera Motore Javascript HTM JS XML, JSON i n t e r n e t File Immagini IMG Fogli di stile CSS CSS Javascript JS Applicazione web (ASP, PHP, JSP, ) SQL Server database DBMS Data base 46

47 Architettura generale del web Server web (Apache, IIS) Dati XML, JSON HTM File HTML IMG Schermo Motore Layout CSS Browser DOM HTM Mouse/ Tastiera Motore Javascript HTM JS i n t Questo è e sufficiente per il sito di ricette r di cucina della nonna n ma nella File e realtà mondo enterprise Javascript è Immagini t molto più complesso XML, JSON IMG Fogli di stile CSS CSS JS Applicazione web (ASP, PHP, JSP, ) SQL Server database DBMS Data base 47

48 The real word is different... The users Functionality Flexibility Portability Reliability Security Integrity Maintenance Performance Scalability Costs Maintenance Development times Interactions with existing systems Interactions with the physical world 48

49 E-business architectures Web Servers Application Servers Database Servers N-tier Site Third-party services Ads Payment Authorization Certification The Internet 49

50 Sito informativo completo 50

51 Ricordiamo i sistemi legacy 51

52 Sito dispositivo schema tipico 52

53 Interagire con altri fornitori L Application Server deve richiamare funzionalità presenti su un sito esterno Servizi dispositivi (es. pagamenti) Servizi informativi (es. stock quotes) Servizi di sicurezza (es. autenticazione) La pagina web contiene delle sezioni provenienti da siti diversi Approccio a portale, le sezioni sono indipendenti (es. igoogle) Approccio applicativo, le sezioni interagiscono e condividono dati (mashup) 53

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