Objectives: Introduction Over View of System Analysis and Design
Describing Data Flows and Data Stores
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- 6.4.2.4 Describing Processes.
| 6.4.2.3 Describing Data Flows and Data Stores The contents of a data flow maybe described by the names) of the data structures(s) that passes along it. In our earlier example, BOOK-DETAILS express the content of the data flow that lead to process 4. Additionally, we may specify the source of the date flow, the destination, and the volume (if any. Using the BOOK- ORDER example, data flows maybe described as follows Data Flow Comments BOOK-DETAILS From Newcomb Hall Bookstore (source) AUTHOR NAME TITLE OF BOOK EDITION Recent edition required QUANTITY Minimum 40 copies A data store is described by the data structures found in it and the data flows that feed it or are extracted from it. For example, the date store BOOKSTORE- ORDER is described by the following contents Comments ORDER Data flow/data structure feeding date store ORDER-NUMBER CUSTOMER DETAILS Content of data store BOOK- DETAIL Data flow/data structure extracted from data store 6.4.2.4 Describing Processes. This step is the logical description. We want to specify the inputs and outputs for the process and summarize the logic of the system. In constructing a data dictionary, the analyst should consider the following points 1. Each unique data flow in the DFD must have one data dictionary entry. There is also a data dictionary entry for each data store and process. 2. Definitions must be readily accessible by name. 3. There should be no redundancy or unnecessary definitions in the data definition. It must also be simple to make updates. 4. The procedure for writing definitions should be straightforward but specific. There should be only one way of defining words. In summary a data dictionary is an integral component of the structured specification. Without a data dictionary, the DFD lacks rigor, and without the DFD, the data dictionary is of no use. Therefore, the correlation between the two is important. Download 0.94 Mb. Share with your friends:
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