Structured Analysis Lec 6 - tructured Systems Analysis:...

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Unformatted text preview: tructured Systems Analysis: tructured Systems Analysis: Structured Systems Analysis: Structured Systems Analysis: Design of Data Stores Design of Data Stores EGA/ERLJ IE 154 Objectives for Today r Know the principles of data store design r Know the different ways to improve data stores r Define and determine data store primary eys keys r Use normalization to improve data stores r Define functional dependencies r Know the steps of normalization r Solve an example Rationale r One of output of the new logical design is the different data stores that need to be improved. r During Systems Design the Data Stores are converted to Databases. r During conversion, analysis of the data stores must be done such that data redundancy can be minimized or even totally removed. Data Store Design Principle r It is usually cheaper and easier to change the logic of a process than to change the structure of a data store. r Hence, the structure of a data store should be as simple and as general as possible Objectives for Today r Know the principles of data store design r Know the different ways to improve data stores r Define and determine data store primary eys keys r Use normalization to improve data stores r Define functional dependencies r Know the steps of normalization r Solve an example Defining the Contents of the New System r 1. look up the data flows going into or out of the data store in the data dictionary to find their component data structures and contents. Compare the contents of the flows going in and out. Make sure all the data content requirements (based on the outflows) of the store can be met by the inflows r 2. Produce a draft of the contents of the data store, based on the analysis of the inflows and outflows. r 3. Simplify the contents by inspection r 4. Simplify the data store by normalization Data Structure: Inflows NEW-EMP EMP-N EMP-M HIRE-D ADDR-T JOB-TITLE-M START-SAL-A EMP-N EMP-N EMP-M TERM ADDR-CHNGE EMP-N EMP-M OLD-ADDR-T NEW-ADDR-T SAL-CHNGE EMP-M OLD-SAL-A NEW-SAL-A EFFCT-D Data Structure: Outflows EMP-ADDR EMP-N MP EMP-N ADDR-T EMP-M CURNT-SAL-A TERM EMP-HIST EMP-N EMP-M HIRE-D JOB-HIST (j) JOB-TITLE-M EFFECT-D SAL-CHNGE (s) SAL-A EFFCT-D Analysis: Additional Inflows ITLE HANGE EMP-N EMP-M LD ITLE TITLE-CHANGE OLD-TITLE-M NEW-TITLE-M EFFECT-D Data Store Contents EMP-N EMP-M ADDR-T CURNT-SAL-A HIRE-D EMP JOB-HIST (j) JOB-TITLE-M EFFECT-D SAL-CHNGE (s) SAL-A EFFCT-D Sample Contents of EMP EMP-N EMP-M ADDR-T CURNT-SAL-A HIRE-D 12321 Dela Cruz, Juan 111, Quezon Ave. QC 21,900 01/01/09 12345 Grande, Miguelito 222, EDSA. Mandaluyong 80,000 01/01/07 JOB-HIST SAL-HIST JOB-TITLE-M EFFECT-D SAL-A EFFCT-D Clerk Programmer 01/01/09 06/06/09 20,400 21,900 01/01/09 06/06/09 Assistant Professor Associate Professor Professor 01/01/07 06/01/07 07/01/08 31,000 50,000 80,000 01/01/07 06/01/07 07/01/08 Revised Data Store EMP-N EMP EMP-M ADDR-T JOB-SAL-HIST (j) JOB-TITLE-M EFFECT-D SAL-A Revised Sample Data Store EMP-N EMP-M ADDR-T JOB-SAL-HIST EFFECT-D JOB-...
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Structured Analysis Lec 6 - tructured Systems Analysis:...

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