Business Information Systems
Business Information Systems ISM 50
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This 12 page Class Notes was uploaded by June Dickinson on Monday September 7, 2015. The Class Notes belongs to ISM 50 at University of California - Santa Cruz taught by John Musacchio in Fall. Since its upload, it has received 87 views. For similar materials see /class/182167/ism-50-university-of-california-santa-cruz in Information Systems Management at University of California - Santa Cruz.
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Date Created: 09/07/15
ISM 50 Business Information Systems Lecture 12 Instructor John Musucchio UC Santa Cruz October 31 2006 Announcements I Read Messerschmitt Ch 7 for Tuesday I Presenters for Thursday n Zhuo H Yang news a Christy Kittnutn Loke news Database Tutorial Sessions Student Talks I Devin Blann news I George Numair news Clien erver Architecture continued lClient Server Example Layers Revealed Server Chem Anpiicciicn Q l lntemet 3Tier Client Server Architecture example Apphcauansexvex Chem 3 ciicxsi kevsmkes 3 Tier ClienT Server ArchiTecTLlre example Application Server Cllml Gateway lnterchange 3 Tier ClienT Server ArchiTecTLlre example Application Server Cllml Si Gateway lnterchange 3 Tier ClienT Server ArchiTecTLlre example A llCalJOn Server Cllml pp lh sdme lmplemehtatldhs gt F l RelaTional DaTabase l DBMS ResponsibiliTies I Hide Changes in The DaTabase hardware from The Application I STandard operaTions on The daTa including searches such a search is called a guerz I SeparaTe DaTabase ManagemenT from ApplicaTions so ThaT many applicaTions can access The same aTa I SecuriTy InTegriTy Backup faLIIT Tolerance eTc I 3 Tier ClienT Server ArchiTecTLlre in General James lhpdts from elleht rDecldEs whattd be ddhe next rDecldEs what shared data El aeeess Application Server and mahlpdlates lt Processes shared data Accept lhstruetlehsm server 7M aka requests of rDlsplay respunses of server rsuppun multlple applleatlehs wlth eemmeh data Protect ehtleal data rDecuuplE data admlhlstratleh ahd applleatleh admlhlstratleh Sun Case continued lWhaT problems did The micro era produce I Deskfops are expensive To maintain D TCO for windows PC 9900 I Every PC had a lot of so 39ware Thaf had To be maintained a Office Windows etc I Small differences like The order in whi so 39ware is insfalled could make differenf PCs behave differenfly i Sun39s Vision Tninclient model Application Servers with Applications written in Java NCs could netnieve applications from application server as needed Applications compatible with any NC hardware and as Applications could be fixed added updated at the server level rather than maintaining each PC iMicrosoff Vision I Keep fatclienfquot mode I Add some feafures To Windows To reduce administrafion cosfs lsyNsTm innni immune I Sun Ntier Asa unm guns or raw mr mm quota m I Sun NTier such mum A Hm umw m mam mu 5 27 587B uan 388m mam I Today I 3tier model common I Sun39s version of 4tier model notcommon I N tier model where Webserver and Application Server on separate equipment also common I Sun39s hardware business not strong a Linux on cheap PCs most common servers in Microsoft desktops replacing Sun workstations I Today I Java in Common in Server implementations I Example Java Servlet implementing application logic in a banking application a Often used to push simple applets onto client a Not common I For big desktop applications I O fice Suite in Java not popular a Microsoft is still in business Architecture Example l Architecture I Conceptualization c What is it you are trying to do I Example Conce t i Small HHC for flight attendants c HHC tells flight attendants which passengers are higher priorit Whopaidthehighestfares who has been a more valuable customer in past c Flight attendant discriminates based on th39s Free drinks meals and pillows to valuable customers Ignore less valuable customers l Example Concept l Architecture I How do you begin to architect a solution for a problem like this I Break it into modules l Architecture l HHC Architecture lllic Application Ammoquot Palm OS Da a I Management Netwumng infrastructure When a module is composed of sub modules the architecture is hierarchica l HHC Architecture HHc Application Anlca on Palm 05 um I management Netwnmng lnrrastructure We are using a lagered architecture as well I Allows reuse of previously built infrastructure l GranulariTy Tradeoff I How big should we make The modules D Many simple small ones D Or a few complicaTed big ones I This aspecT of modulariTy is called ganderfr I Which is beTTer l HHC Server I Communication with HHC Computation HHC Server Applicatio of key statistics Windbws OS N etvvurking intrastructure Again we see layering and hierarchy Between each mbduie we speeiry an intenfaee m munication with airline Standard Database queries SOL relayed tb DBMS via US and infrastructure l DaTa server Standard Database queries SOL rrbrn HHC Server Database Our architecture makes use at the Existing interface at the airline database WE dbn t need tci redesign iti A simple inTerface from wiThin our HHC Server ArchiTecure Compute Mean and Variance List at nurnbers Computation Mean ofkey statistics Variance I quotEif l InTer39faces Compute Mean and N nurnbers cit Variance Fibattybe mpumioquot 2 Numbers brribat ofkey statistics We that SDNW Mean Variance InTerface specifcaTions are ofTen made precise by us n9 duh Gus Example Type floaT d numberwi hadecimal place d Has a eentain alluwable range and precisiun gt l More on DaTa Types I DaTa passing an inTerface is ofTen specified in Terms of a limiTed number of sTandard daTa Types I DaTa Type range of values and allowable manipulaTion I DaTa Type does naf presume a specific represenTaTion To allow heTerogeneous planorms a RepresenTaTion musT be known when daTa passes a specific module inTerface l Example daTa Types Integer a natural number beTween 32 767 and 32 768quot u Could be represented in many ways by 16 biTs snce 6 536 Float a number of The form quotMW32768 where mis in T 9 he ran e 32 767 To 32 768 and quotis in The range 255 To 256quot u Could be represented by 168 24 biTs i More daTa Types CharacTer ll values assuming a z and AZ plus space and punctuation marksquot could be represented by 7 or 8 biTs CharacTer sTring ll collection of ncharacters where I7 is customizablequot could be represented by 7quot biTs l Compound daTa Types Programmerdefined composiTian of basic daTa Types STring address Integer yearof birTh lImplemenTaTion WM Compute Mean and Variance 9 lmplementatiunl ModuleA of key statls I One module should not be concerned with other module39s implementation a 9 Separation of conc rns One module should see the other only through its interface implementation details hidden a gt Abstraction l InTer39faces N numbers at I Eluattype 39 Compute Mean and Variance 2 Numbers at fluat type that slgnlty Mean Varlance NTERFACE lImplemenTaTion WM Compute Mean and ananc ale Module A lmplementatiun 2 Computation of key statistics SUM MEAN VARIANCE Though different this implementation is ok too e n choose the implementation details however we want as long as we comply with the agreed nterface ModuleE l Implementation ooin pute Mean and Variance Module A Computation of key statistics quotl HEEd El QEHHE sum VARIANCE r J quotMEAhUE l lllusitake ltfrum Equot I Should he use it a NO Why I Either A should compute quotSUMquot himself or sit down with B and redesign the interface l Encapsulation I The designer of B might take measures to hide quotSUMquot from A so that A is not able to violate the agreed interface ll Example B does not declare quotSUMquot as a global 39able I Making a modules implementation details inaccessible to other modules is called encagsuafon l Interfaces PARAM ETERS N nurnpers er afloat type o Muuule El ooin pute Mean and Variance M udule A Numbers at tluat type tnat signiiy Meari Varlanee lNTERFACE Tiiis sim ale interface example allows for only one action of modu e in Action is Compute mean and variancequot inputatio of key statistics Other examples are possible l Possible software interface action1 Menu of actions acti0n2 action 3 Example Action 1 Compute mean Action 2 Compute variance Action 3 Compute mode Etc l Protocol In addition to atomic actions an interface may define protocols ll Protocol finite sequence of actions required to achieve a higher level function ll One action can be shared by multiple protocols ll Multiple modules may participate in a protocol l Protocol Example H l rntne HHC ut ellu Airplanel 234 Hellu l rntne ate 32 SEN r tnese were tne unruly passengers on lasttlignt Passengers neteu Tell rne apeuttne passengers at rny nexttlignt Might be passed As an array or a M eampaunu data type Data ii SE r ii T apuut tne vyeatner t ell rne at rny next des tlna ien mm 39 string Return Weatner Data l Another Interface Example Automatic teller machine ATM lInterface building blocks Message on screen or printe a Menu of actions or returns from an action a Touch selection of action Keypad u Input parameters to an action Card reader a Authentication input parameters Money output slot u Returns money l Action authentication Parameters u Identity card in slot u Institution card in slot a PIN typed on keypad Internally it contacts institution and matches against its database institution noted for all subsequent actions example of state Retu n a Screen message Invalid PINquot or menu of available actions l Steps Define available actions Define for each higher level function a protocol in Single action or a finite sequence of actions l Action authentication Parameters Internal functionality Returns l Action specifyaccount Parameters Internal functionality Returns l AcTion specifyaccounT ParameTers u AccounT Touch screen from menu of choices InTernally choice noTed for all subsequenT acTions anoTher example of sTaTe ReTurns is None l ProTocol cashwiThdrawal WhaT is The sequence of acTions l AcTion amounT ParameTers u DollarsandcenTs Typed on keypad InTernally amounT noTed anoTher example of sTaTe ReTurns a Success or failure sTaTe dependenT for example for a wiThdraw failure when dollarsandcenTs exceeds balance l ProTocol cashwiThdrawal failure other objectives no accounts balance exceeded More on layering by David G Messerschm iTT l Goals UndersTand beTTer u how layering is used in The infrasTrucTure u how iT conTains complexiTy u how iT coordinaTes supplier in how iT allows new capabiliTies To be added incremenTally 10 Inferac hon of layers Layer eeEye s e cheer a the ayer be uw I I I Each ayer Druv des semees m the ayer eeEye ey utmzmg the semees a the ayer be uw and seeme eepeemey I I I I Layer be uw es es s sewer m the ayer eeEye Layering Exxshng layer c9 lt c9 c9 Le enng buxldg capabx ny incrementally by addndg a what exists IThr ee Types of sof rwar e APP Can an ltsmpsnems em framewurk What m emmn am ng Bthtanun 391nfrastructure E e semees esmmumeeusn smeee nee vareientahun em Part of M39cr osof f vs DOST dispufe Mcrugu D01 1 Mann lMajor layers l Data and information Application Deals with information i Assumes structure and interpretation i Ignores structure and interpretation Infrastructure Deals with data l Data and information in layers I The infrastructure should deal with data a or at most minimal structure and interpretation I The application adds additional structure and interpretation I This yields a separation of concerns lPackage file message In the simplest case the infrastructure deals with a package of data nonstandard terminology a collection of bits a specified number and ordering The objective of the infrastructure is to store and communicate packages while maintaining data inteng y File for storage message for communication l Data integrity Retain the a values a order a number of bits in a package l Example 1 Sup sends a letter to Alice E42 snipping Container AECAlrllnes l Example 2 Web page Web server Web browser Application Operating system File system Network Assembly 12
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