Chapter 1 Fundamentals

© 2006 Pearson Addison-Wesley. All rights reserved. 1-2 인터넷 응용프로그래밍 평가방법 – 중간고사 15%, 기말고사 10%, 실기시험 20% – 리포트 15% – 쪽지시험, 기타 5% – 과제 35% 과제 –ABEEK( 설계 1 학점 ) 과 삼성 트랙 – 각자 자신이 인터넷 상거래 사이트를 만든다고 생각하고, – 그에 대해 먼저 설계하고 차례로 만듦 – 채점기준 » 계획의 구체성 » 완성도 » 창의성 – 순서 »1-2 주 : 1 차 설계도 완성 ( 클라이언트와 서버를 구별하여 설계 ) »3 주 : 제시 내용에 따라 평가결과를 주면 그에 따라 재설계 »4-5 주 : XHTML 을 이용하여 구현 »6-7 주 : Java Script 를 이용한 확장 »8-9 주 : XML 을 이용한 재구현 »10-13 주 : 서버 사이트 구현 »14- 제출과 평가

© 2006 Pearson Addison-Wesley. All rights reserved. 1-3 인터넷 Internet & World Wide Web Protocols –network layers –TCP/IP »domain name system, IP addresses, routing protocols –HTTP »GET/POST, headers, caching, cookies Web2.0 Sematic Web Web Service 사이트 – ( 강의노트 ) – – – – -20-vs-semantic-web-vs-rdfhttp://ebiquity.umbc.edu/blogger/2006/05/12/web -20-vs-semantic-web-vs-rdf – 그 외에 상거래 사이트 등

© 2006 Pearson Addison-Wesley. All rights reserved. 1-4 자료조사 Google 의 다양한 기능 조사 Wikipidia 의 기능 조사 인터넷, 미래넷 – 생각이 바뀌어야 한다. » 소비자의 변화를 읽는다. 대량생산에 의한 가격 경쟁, 상표 경쟁에서 » 삼성전자 이건희폰, 블루블랙폰 » 모토롤라 레이저폰 – 끝은 없다. »Yahoo »Google – 틈새 시장이 크다. » 레코드 판매 » 분야에서 최고를 유지한다.

© 2006 Pearson Addison-Wesley. All rights reserved A Brief Intro to the Internet Origins – DoD ARPAnet - late 1960s and early 1970s » Network reliability »For ARPA-funded research organizations * Advanced Research Project Agency BITnet, CSnet - late 1970s & early 1980s – and file transfer for other institutions NSFnet –Originally for non-DOD funded places –Initially connected five supercomputer centers –By 1990, it had replaced ARPAnet for non-military uses –Soon became the network for all (by the early 1990s) –NSFnet eventually became known as the Internet What the Internet is: –A world-wide network of computer networks –At the lowest level, since 1982, all connections use TCP/IP »Transmission Control Protocol »Internet Protocol TCP/IP hides the differences among devices connected to the Internet

© 2006 Pearson Addison-Wesley. All rights reserved A Brief Intro to the Internet (continued) - Internet Protocol (IP) Addresses - Every node has a unique numeric address - Form: 32-bit binary number - New standard, IPv6, has 128 bits (1998) - Organizations are assigned groups of IPs for their computers - Domain names - Form: host-name.domain-names - First domain is the smallest; last is the largest - Last domain specifies the type of organization - Fully qualified domain name - the host name and all of the domain names - DNS servers - convert fully qualified domain names to IPs - Problem: By the mid-1980s, several different protocols had been invented and were being used on the Internet, all with different user interfaces (Telnet, FTP, Usenet, mailto

© 2006 Pearson Addison-Wesley. All rights reserved. 1-7 IP addresses IP addresses are 32 bits long ↓ written as a dotted sequence divided into 5 classes –class A: start with 0, then 7-bit code »2 24 = 16,777,216 hosts in subnetwork –class B: start with 10, then 14-bit code »2 16 = 65,536 hosts in subnetwork –class C: start with 110, then 21-bit code »2 8 = 256 hosts in subnetwork –class D: start with 1110 »used for multicasting –class E: start with »reserved for future use IPv6 extends address size to 128 bits –extensions support authentication, data integrity, confidentiality

© 2006 Pearson Addison-Wesley. All rights reserved. 1-8 Global addresses Question: What are the challenges? Wish List: Addresses are unique. Address structure makes routing/forwarding as easy as possible. CLASS A CLASS B CLASS C

© 2006 Pearson Addison-Wesley. All rights reserved. 1-9 TCP/IP

© 2006 Pearson Addison-Wesley. All rights reserved The World-Wide Web - A possible solution to the proliferation of different protocols being used on the Internet - Origins - Tim Berners-Lee at CERN proposed the Web in 1989 : Purpose: to allow scientists to have access to many databases of scientific work through their own computers * CERN: Conseil Européen pour la Recherche Nucléaire, or European Council for Nuclear Research - Document form: hypertext - Pages? Documents? Resources? : We’ll call them documents - Hypermedia – more than just text – images, sound, etc. - Web or Internet? - The Web uses one of the protocols, http, that runs on the Internet--there are several others ( telnet, mailto, etc.)

© 2006 Pearson Addison-Wesley. All rights reserved Web Browsers - Mosaic - NCSA (Univ. of Illinois), in early First to use a GUI, led to explosion of Web use - Initially for X-Windows, under UNIX, but was ported to other platforms by late 1993 * NCSA: National Center for Supercomputing Applications National Center for Supercomputing Applications - Browsers are clients - always initiate, servers react (although sometimes servers require responses) - Most requests are for existing documents, using HyperText Transfer Protocol (HTTP) - But some requests are for program execution, with the output being returned as a document 1.4 Web Servers - Provide responses to browser requests, either existing documents or dynamically built documents - Browser-server connection is now maintained through more than one request-response cycle

© 2006 Pearson Addison-Wesley. All rights reserved Web Servers (continued) - All communications between browsers and servers use Hypertext Transfer Protocol (HTTP) - Web servers run as background processes in the operating system - Monitor a communications port on the host, accepting HTTP messages when they appear - All current Web servers came from either 1. The original from CERN 2. The second one, from NCSA - Web servers have two main directories: 1. Document root (servable documents) 2. Server root (server system software) - Document root is accessed indirectly by clients - Its actual location is set by the server configuration file - Requests are mapped to the actual location -Virtual document trees - Virtual hosts

© 2006 Pearson Addison-Wesley. All rights reserved Web Servers (continued) - Proxy servers - Web servers now support other Internet protocols - Apache (open source, fast, reliable) - Directives (operation control): ServerName ServerRoot ServerAdmin, DocumentRoot Alias Redirect DirectoryIndex UserDir - IIS (Microsoft’s Internet Information Server) - Operation is maintained through a program with a GUI interface

© 2006 Pearson Addison-Wesley. All rights reserved URLs - General form: scheme:object-address - The scheme is often a communications protocol, such as telnet or ftp - For the http protocol, the object-address is: fully qualified domain name / doc path - For the file protocol, only the doc path is needed - Host name may include a port number, as in zeppo:80 ( 80 is the default, so this is silly) - URLs cannot include spaces or any of a collection of other special characters (semicolons, colons,...) - The doc path may be abbreviated as a partial path - The rest is furnished by the server configuration : : - If the doc path ends with a slash, it means it is a directory

© 2006 Pearson Addison-Wesley. All rights reserved Multipurpose Internet Mail Extensions (MIME) - Originally developed for - Used to specify to the browser the form of a file returned by the server (attached by the server to the beginning of the document) - Type specifications - Form: type/subtype - Examples : text/plain, text/html, image/gif, image/jpeg, video/mpeg, video/quicktime - Server gets implicitly type from the requested file name’s suffix (.html implies text/html ) - Browser gets the type explicitly from the server : MIME header - Experimental types - Subtype begins with x- e.g., video/x-msvideo - Experimental types require the server to send a helper application or plug-in so the browser can deal with the file

© 2006 Pearson Addison-Wesley. All rights reserved The HyperText Transfer Protocol - The protocol used by ALL Web communications : HTTP, RFC 2616 (June 1999, W3C) - Request Phase - Form: HTTP method domain part of URL HTTP ver. Header fields blank line Message body - An example of the first line of a request: GET /cs.uccp.edu/degrees.html HTTP/1.1 - Most commonly used methods: GET - Fetch a document POST - Execute the document, using the data in body HEAD - Fetch just the header of the document PUT - Store a new document on the server DELETE - Remove a document from the server

© 2006 Pearson Addison-Wesley. All rights reserved The HyperText Transfer Protocol (continued) - Four categories of header fields: General, request, response, & entity - Common request fields: Accept: text/plain Accept: image/gif Accept: text/* If-Modified_since: date - Common response fields: Content-length: 488 : POST 를 위해 필요 Content-type: text/html -Can communicate with HTTP without a browser > telnet blanca.uccs.edu http GET /respond.html HTTP/1.1 Host: blanca.uccs.edu

© 2006 Pearson Addison-Wesley. All rights reserved The HyperText Transfer Protocol (continued) - Response Phase - Form: Status line Response header fields blank line Response body - Status line format: HTTP version status code explanation - Example: HTTP/ OK (Current version is 1.1) - Status code is a three-digit number; first digit specifies the general status 1 => Informational 2 => Success 3 => Redirection 4 => Client error 5 => Server error - The header field, Content-type, is required

© 2006 Pearson Addison-Wesley. All rights reserved The HyperText Transfer Protocol (continued) - An example of a complete response header: HTTP/ OK Date: Tues, 18 May :45:13 GMT Server: Apache (Red-Hat/Linux) Last-modified: Tues, 18 May :38:38 GMT Etag: "841fb-4b-3d1a0179" Accept-ranges: bytes Content-length: 364 Connection: close Content-type: text/html, charset=ISO Both request headers and response headers must be followed by a blank line - HTTP/ Not Found

© 2006 Pearson Addison-Wesley. All rights reserved Caching browsers cache pages to save downloading –maintain temporary storage (cache) for recent pages –when a page is requested, check to see if already in cache –if not in the cache, issue GET request »when response message arrives, display page and store in cache (along with header info) –if already stored in the cache, send GET request with If-Modified-Since header set to the data of the cached page »when response message arrives, if status code 200, then display and store in cache if status code 304, then display cached version instead

© 2006 Pearson Addison-Wesley. All rights reserved Cookies Netscape ’ s solution: cookies –a cookie is a collection of information about the user –server can download a cookie to the client ’ s machine using the “ Set-cookie ” header in a response Set-cookie: CUSTOMER=Dave_Reed; PATH=/; EXPIRES=Thursday, 29-Jan-04 12:00:00 –when user returns to URL on the specified path, the browser returns the cookie data as part of its request Cookie: CUSTOMER=Dave_Reed HTTP message passing is transaction-based, stateless  many e-commerce apps require persistent memory of customer interactions e.g., amazon.com remembers your name, credit card, past purchases, interests

© 2006 Pearson Addison-Wesley. All rights reserved The Web Programmer’s Toolbox - XHTML - To describe the general form and layout of documents - An XHTML document is a mix of content and controls - Controls are tags and their attributes - Tags often delimit content and specify something about how the content should be arranged in the document - Attributes provide additional information about the content of a tag - Tools for creating XHTML documents - XHTML editors - make document creation easier - Shortcuts to typing tag names, spell-checker, - WYSIWYG XHTML editors - Need not know XHTML to create XHTML documents

© 2006 Pearson Addison-Wesley. All rights reserved The Web Programmer’s Toolbox (continued) - Plug ins - Integrated into tools like word processors, effectively converting them to WYSIWYG XHTML editors - Filters - Convert documents in other formats to XHTML - Advantages of both filters and plug-ins: - Existing documents produced with other tools can be converted to XHTML documents - Use a tool you already know to produce XHTML - Disadvantages of both filters and plug-ins: - XHTML output of both is not perfect - must be fine tuned - XHTML may be non-standard - You have two versions of the document, which are difficult to synchronize

© 2006 Pearson Addison-Wesley. All rights reserved The Web Programmer’s Toolbox (continued) - XML - A meta-markup language - Used to create a new markup language for a particular purpose or area - Because the tags are designed for a specific area, they can be meaningful - No presentation details - A simple and universal way of representing data of any textual kind - JavaScript - A client-side HTML-embedded scripting language - Only related to Java through syntax - Dynamically typed and not object-oriented - Provides a way to access elements of HTML documents and dynamically change them

© 2006 Pearson Addison-Wesley. All rights reserved The Web Programmer’s Toolbox (continued) - Java - General purpose object-oriented programming language - Based on C++, but simpler and safer - Our focus is on applets, servlets, and JSP - Perl - Provides server-side computation for HTML documents, through CGI - Perl is good for CGI programming because: - Direct access to operating systems functions - Powerful character string pattern-matching operations - Access to database systems - Perl is highly platform independent, and has been ported to all common platforms - Perl is not just for CGI

© 2006 Pearson Addison-Wesley. All rights reserved The Web Programmer’s Toolbox (continued) - PHP - A server-side scripting language - An alternative to CGI - Similar to JavaScript - Great for form processing and database access through the Web -RDF, OWL Resource Description Framework Web Ontology Language