Chapter12 - Chapter 12: Information Systems Information...

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Unformatted text preview: Chapter 12: Information Systems Information systems are software applications that facilitate the organization and analysis of data. Example: Spreadsheet software allows users to place raw data in tables and then utilize formulas and basic graphical mechanisms to generate calculations and Chapter 12 Information Systems Page 1 Database Structures An alternative to a distributed information system based upon files is a centralized system based upon the concept of databases. File-Oriented System Renta l Dept. Sales Dept. Purch -asing Dept. Marketing Dept. Maintenanc e Dept. Payro ll Dept. Rental Dept. Database-Oriented System Sales Dept. Purchasing Dept. Video Rental Files Video Sales Files Video Purchas e Files Advertis ement Files Store Upkeep Files Store Personne l Files Integrated Database Payroll Dept. Marketing Dept. DISADVANTAGES OF EACH SYSTEM File-Oriented Duplication of effort Multiple error sources Maintenanc e Dept. Database-Oriented Data security problems Widespread error effects Chapter 12 Information Systems Page 2 A Modular View of a Database System The DBMS uses schema and subschema to ensure data security. A schema describes the way the entire database is organized. A subschema describes the organization of the portion of the database that is accessible to a particular type of user. Chapter 12 Information Systems Page 3 The Relational Database Model Name Moose Bear Coyote Hound Gorilla Pig The simplest conceptual arrangement of a database uses a table of rows (called tuples) and columns (called attributes).First Last M.I. SID Hr Clas GP Major DOB Image Name Bullwinkle Yogi Wile Huckleberr y Magilla Porky J D E H B P 90062697 7 90012987 5 90070554 8 90033922 7 90018701 4 90088263 5 s 112 48 54 75 102 66 s Sr So So Jr Sr Jr A 3.24 2.17 3.16 3.05 3.76 2.38 CHEM BIOL MATH MKTG ELED ECON 03/21/7 6 02/16/7 9 11/05/8 1 09/12/8 3 12/12/8 0 05/02/8 2 The major advantage of this model is its logical conceptualization. The major disadvantage is the substantial amount of software and hardware overhead required to maintain and access the table. Chapter 12 Information Systems Page 4 Relational Operator SELECT The SELECT operation determines which tuples have particular attributes. ORIGINAL TABLE Code 213345 311452 254467 309772 256568 290031 Description 9v Battery Power Drill 60W Bulb Mini-Ratchet Set Halogen Light Flat Screwdriver Price 1.92 34.99 1.47 6.50 12.99 8.45 NEW TABLE Code Apply SELECT with Price < 10.00 213345 254467 309772 290031 Description 9v Battery 60W Bulb Mini-Ratchet Set Flat Screwdriver Price 1.92 1.47 6.50 8.45 Chapter 12 Information Systems Page 5 Relational Operator PROJECT The PROJECT operation limits the scope of the database to specific attributes. ORIGINAL TABLE Code 213345 311452 254467 309772 256568 290031 Description 9v Battery Power Drill 60W Bulb Mini-Ratchet Set Halogen Light Flat Screwdriver Price 1.92 34.99 1.47 6.50 12.99 8.45 NEW TABLE Code Apply PROJECT with Code & Price 213345 311452 254467 309772 256568 290031 Price 1.92 34.99 1.47 6.50 12.99 8.45 Chapter 12 Information Systems Page 6 Relational Operator JOIN The JOIN operation combines multiple tables that have common attributes. Table CUSTOMER CusN o 113244 5 132124 2 165739 9 Table SALESREP RepN o 231 125 231 167 421 CusNam CusZi e p Walker Rodrigue z Vanloo 62449 62025 62363 62294 62025 RepID 125 167 231 RepPhon e 618243988 7 618342677 8 618243112 4 Apply JOIN with CUSTOMER.RepNo = SALESREP.RepID 131224 Rakowski 3 154231 1 121778 2 Smithson Adares CusNo NEW 314526775 TABLE 333 CusNam CusZi 9 RepNo e p 62449 62025 62363 62294 231 125 231 167 RepPhone 6182431124 6182439887 6182431124 6183426778 Chapter 12 Information Systems Page 7 1132445 Walker 62650 125 1321242 Rodriguez 1657399 1312243 Vanloo Rakowski Concurrency Control A potential problem with database systems that allow multiple access points is the loss of data integrity. At ATM #1: Deposit Get Balance... $400 $500$400 to Balance... Add $900 new Balance... Store $900 $500 Subtract $200 from Balance... $300 new Balance... Store $300 Either balance that's stored would be incorrect, since the correct balance is $700! At ATM #2: Withdraw Get Balance... $200 Chapter 12 Information Systems Page 8 Databases and Privacy The proliferation of information on database systems poses a potential threat to the privacy of people about whom the data refers. Example: Medical Databases Reduction of paperwork Employer access might cost Fewer false insurance claims jobs Facilitates disease tracking "High risk" insurance Immediate access in increases Unsolicited advertisements emergency Cost-effective ID of treatment Fear inhibits candid Safer than paper records disclosure Inaccuracies are spread Advantages: Disadvantages: Chapter 12 Information Systems Page 9 Cryptography Networks are set up to send messages right past stations that aren't authorized to read them, but what's to prevent such unauthorized viewing? Message The most common solution to this problem is encryption, where the message is coded in such a way that only the receiving station can decode it. Chapter 12 Information Systems Page 10 Public-Key Encryption I have affixed to me the dirt and dust of countless ages! Chuck Linus Lucy Patty 1. Create Message mdbriugndlwg mamnsgfyddkd qhgwdnchsgsh ahwbsgcydhzx 2. Look Up Recipient's Public Key xsjb2dhdkWb$xzdu Ydm! dj5slLssghd8nd&hsn qabi?dsjsg% 3. Encrypt Message With Recipient's Public Key 4. Transmit Encrypted Message I have affixed to me the dirt and dust of countless ages! xsjb2dhdkWb$xzdu Ydm! dj5slLssghd8nd&hsn qabi?dsjsg% 5. Decrypt Message With Recipient's Private Key Chapter 12 Information Systems Page 11 Key-BasedisAuthenticationbe sure who it When a message received, how can you came from? I'm going to recruit that funny looking kid who plays shortstop on Chuck's team! Ma3ndhvyr#bcjaqwpfQkgui orkfohskxi8vce %fpgkjfhikfvdamxxyemfidey chssfhsgdhahdm$dlglyn7buc hso 1. Create Message 3. Transmit Encrypted Message I'm going to recruit that funnylooking kid who plays shortstop on Chuck's team! 2. Encrypt Message With Sender's Private Key Ma3ndhvyr#bcjaqwpfQkgui orkfohskxi8vce %fpgkjfhikfvdamxxyemfidey chssfhsgdhahdm$dlglyn7buc hso 4. Decrypt Message With Sender's Public Key Chapter 12 Information Systems Page 12 ...
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