Distributed System by Pratik Tambekar
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The document discusses different document models used on the web and in Lotus Notes. It provides examples of HTML, XML, and Notes documents. It also summarizes key architectural aspects of web clients and servers as well as the overall organization and processes used in Lotus Notes.
Distributed System by Pratik Tambekar
- 2. The World Wide Web Overall organization of the Web.
- 3. Document Model (1) A simple Web page embedding a script written in JavaScript. <HTML> <!- Start of HTML document --> <BODY> <!- Start of the main body --> <H1>Hello World/H1> <!- Basic text to be displayed --> <P> <!- Start of a new paragraph --> <SCRIPT type = "text/javascript"> <!- identify scripting language --> document.writeln ("<H1>Hello World</H1>; // Write a line of text </SCRIPT> <!- End of scripting section --> </P> <!- End of paragraph section --> </BODY> <!- End of main body --> </HTML> <!- End of HTML section -->
- 4. Document Model (2) An XML definition for referring to a journal article. (1) <!ELEMENT article (title, author+,journal)> (2) <!ELEMENT title (#PCDATA)> (3) <!ELEMENT author (name, affiliation?)> (4) <!ELEMENT name (#PCDATA)> (5) <!ELEMENT affiliation (#PCDATA)> (6) <!ELEMENT journal (jname, volume, number?, month? pages, year)> (7) <!ELEMENT jname (#PCDATA)> (8) <!ELEMENT volume (#PCDATA)> (9) <!ELEMENT number (#PCDATA)> (10) <!ELEMENT month (#PCDATA)> (11) <!ELEMENT pages (#PCDATA)> (12) <!ELEMENT year (#PCDATA)>
- 5. Document Model (3) An XML document using the XML definitions from previous slide (1) <?xml = version "1.0"> (2) <!DOCTYPE article SYSTEM "article.dtd"> (3) <article> (4) <title> Prudent Engineering Practice for Cryptographic Protocols</title> (5) <author><name>M. Abadi</name></author> (6) <author><name>R. Needham</name></author> (7) <journal> (8) <jname>IEEE Transactions on Software Engineering</jname> (9) <volume>22</volume> (10) <number>12</number> (11) <month>January</month> (12) <pages>6 – 15</pages> (13) <year>1996</year> (14) </journal> (15) </article>
- 6. Document Types Six top-level MIME types and some common subtypes. Type Subtype Description Text Plain Unformatted text HTML Text including HTML markup commands XML Text including XML markup commands Image GIF Still image in GIF format JPEG Still image in JPEG format Audio Basic Audio, 8-bit PCM sampled at 8000 Hz Tone A specific audible tone Video MPEG Movie in MPEG format Pointer Representation of a pointer device for presentations Application Octet-stream An uninterrupted byte sequence Postscript A printable document in Postscript PDF A printable document in PDF Multipart Mixed Independent parts in the specified order Parallel Parts must be viewed simultaneously
- 7. Architectural Overview (1) The principle of using server-side CGI programs.
- 8. Architectural Overview (2) An HTML document containing a JavaScript to be executed by the server (1) <HTML> (2) <BODY> (3) <P>The current content of <pre>/data/file.txt</PRE>is:</P> (4) <P> (5) <SERVER type = "text/javascript"); (6) clientFile = new File("/data/file.txt"); (7) if(clientFile.open("r")){ (8) while (!clientFile.eof()) (9) document.writeln(clientFile.readln()); (10) clientFile.close(); (11) } (12) </SERVER> (13) </P> (14) <P>Thank you for visiting this site.</P> (15) </BODY> (16) </HTML>
- 9. Architectural Overview (3) Architectural details of a client and server in the Web.
- 10. HTTP Connections a) Using nonpersistent connections. b) Using persistent connections
- 11. HTTP Methods Operations supported by HTTP. Operation Description Head Request to return the header of a document Get Request to return a document to the client Put Request to store a document Post Provide data that is to be added to a document (collection) Delete Request to delete a document
- 12. HTTP Messages (1) HTTP request message
- 13. HTTP Messages (2) HTTP response message.
- 14. HTTP Messages (3) Some HTTP message headers. Header Source Contents Accept Client The type of documents the client can handle Accept-Charset Client The character sets are acceptable for the client Accept-Encoding Client The document encodings the client can handle Accept-Language Client The natural language the client can handle Authorization Client A list of the client's credentials WWW-Authenticate Server Security challenge the client should respond to Date Both Date and time the message was sent ETag Server The tags associated with the returned document Expires Server The time how long the response remains valid From Client The client's e-mail address Host Client The TCP address of the document's server If-Match Client The tags the document should have If-None-Match Client The tags the document should not have If-Modified-Since Client Tells the server to return a document only if it has been modified since the specified time If-Unmodified-Since Client Tells the server to return a document only if it has not been modified since the specified time Last-Modified Server The time the returned document was last modified Location Server A document reference to which the client should redirect its request Referer Client Refers to client's most recently requested document Upgrade Both The application protocol the sender wants to switch to Warning Both Information about the status of the data in the message
- 15. Clients (1) Using a plug-in in a Web browser.
- 16. Clients (2) Using a Web proxy when the browser does not speak FTP.
- 17. Servers General organization of the Apache Web server.
- 18. Server Clusters (1) The principle of using a cluster of workstations to implement a Web service.
- 19. Server Clusters (2) (a) The principle of TCP handoff.
- 20. Server Clusters (3) (b) A scalable content-aware cluster of Web servers.
- 21. Uniform Resource Locators (1) Often-used structures for URLs. a) Using only a DNS name. b) Combining a DNS name with a port number. c) combining an IP address with a port number.
- 22. Uniform Resource Locators (2) Examples of URLs. Name Used for Example http HTTP http://www.cs.vu.nl:80/globe ftp FTP ftp://ftp.cs.vu.nl/pup/minx/README file Local file file:/edu/book/work/chp/11/11 data Inline data data:text/plain;charset=iso-8859-7,%e1%e2%e3 telnet Remote login telnet://flits.cs.vu.nl tel Telephone tel:+31201234567 modem Modem modem:+31201234567;type=v32
- 23. Uniform Resource Names The general structure of a URN
- 24. Web Proxy Caching The principle of cooperative caching
- 25. Server Replication The principle working of the Akami CDN.
- 26. Security (1) The position of TLS in the Internet protocol stack.
- 27. Security (2) TLS with mutual authentication.
- 28. Lotus Notes The general organization of a Lotus Notes system.
- 29. Document Model Examples of different types of notes. Note type Category Description Document Data A user-oriented document such as a Web page Form Design Structure for creating, editing, and viewing a document Field Design Defines a field shared between a form and subforms View Design Structure for displaying a collection of documents ACL Administration Contains an access control list for the database ReplFormula Administration Describes the replication of the database
- 30. Processes (1) The general organization of a Domino server.
- 31. Processes (2) Request handling in a cluster of Domino servers.
- 32. Naming A Notes URL for accessing a database.
- 33. Identifiers Some major identifiers in Notes. Identifier Scope Description Universal ID World Globally unique identifier assigned to each note Originator ID World Identifier for a note, but includes history information Database ID Server Time-dependent identifier for a database Note ID Database Identifier of a note relative to a database instance Replica ID World Timestamp used to identify the same copies of a database
- 34. Replication Replication schemes in Notes. Scheme Description Pull-push A replicator task pulls updates in from a target server, and pushes its own updates to that target as well Pull-pull A replicator task pulls in updates from a target server, and responds to update fetch requests from that target Push-only A replicator task only pushes its own updates to a target server, but does not pull in any updates from the target Pull-only A replicator only pulls in updates from a target server, but does not push any of its own updates to that target
- 35. Conflict Resolution Safely merging two documents with conflicting OIDs.
- 36. Authentication: Validating Certificates Public-key validation in Notes
- 37. Access Control Parts in Notes subject to access control. Part Description Servers ACLs specifying access rights for servers and ports Workstations Lists specifying execution rights for scripts and such Databases ACLs specifying permissions for different types of users Files ACLs used for controlling access by Web clients Design notes ACLs to control the presentation and such of documents Documents ACLs to control read and and write access to documents
- 38. Comparison of Web & Lotus Notes Issue WWW Notes Basic model Marked-up text List of text items (note) Extensions Multimedia, scripts Multimedia, scripts Storage model File oriented Database oriented Network comm. HTTP RPC, E-mail Interprocess comm. Operating sys. dependent Notes Object Services (NOS) Client process Browser, Editor Browser, Design editor Client extensions Plug-ins In basic client system Server process Comparable to file server Comparable to database server Server extensions Servlets, CGI programs Server tasks Server clusters Transparent Nontransparent Naming URNs, URLs URLs, identifiers Synchronization Mainly local Mainly local Caching Advanced Not documented Replication Mirroring, CDNs Lazy Fault tolerance Reliable comm. & clusters Clusters Recovery No explicit support Single server Authentication Mainly TLS Certificate validation Access control Server dependent Extensive ACLs