![]() ![]() The information, however, may be stored in numerous places, and in each place the data store may be different. This information is described in data structures. Up to now, we have determined what data needs to flow from one process to another. Developing Data StoresĪnother activity in creating the data dictionary is developing data stores. An example of an input/output analysis form for World’s Trend Catalog Division. In this example of a CUSTOMER BILLING STATEMENT, the CUSTOMER FIRST NAME, CUSTOMER LAST NAME, and CUSTOMER MIDDLE INITIAL should be grouped together in a structural record. These considerations can be seen in the completed Input and Output Analysis Form for World’s Trend Catalog Division (see figure below). Elements that fall into a group or that regularly combine with several other elements in many structures should be placed together in a structural record. Once the form has been completed, each element should be analyzed to determine whether the element repeats, whether it is optional, or whether it is mutually exclusive of another element. A list of elements, including their names, lengths, and whether they are base or derived, and their editing criteria.Elements indicating the sequence of the data on a report or screen (perhaps in columns).In the logical design stage, the format may be undetermined. The user contact responsible for further details clarification, design feedback, and final approval.Examples are CUSTOMER BILLING STATEMENT and CUSTOMER DETAILS INQUIRY. If the analyst is working on the physical design or if the user has explicitly stated the nature of the input or output, however, the name should include that information regarding the format. If the data flow is on a logical diagram, the name should identify what the data are (for example, CUSTOMER INFORMATION). A descriptive name for the input or output.Input and output analysis forms contain the following commonly included fields: Analyzing Input and OutputĪn important step in creating the data dictionary is to identify and categorize system input and output data flow. Similarly, GROSS PAY(output from process 5.3.4, a lower-level process not shown in the figure) is contained in the structural record CURRENT PAYAMOUNTS (output from the parent process 5.3, COMPUTE CURRENT PAYAMOUNTS). Returning to the example, WAGE INFORMATION (input into process 5.3, COMPUTE CURRENT PAYAMOUNTS) is a structural record contained in the EMPLOYEE RECORD (input to process 5). It is important that the data flow names on the child data flow diagram are contained as elements or structural records in the data flow on the parent process. Two data flow diagrams and corresponding data dictionary entries for producing an employee paycheck. Similarly, TIMEFILE RECORD and the EMPLOYEE PAYCHECK are also defined as a series of structures. The corresponding data dictionary entry for EMPLOYEE RECORD shows the EMPLOYEE NUMBER and four structural records, the view of the data obtained early in the analysis. Process 5, found on Diagram 0, is an overview of the production of an EMPLOYEE PAYCHECK. As child diagrams are created, the data flow into and out of the processes becomes more and more detailed, including structural records and elements.įigure below illustrates a portion of two data flow diagram levels and corresponding data dictionary entries for producing an employee paycheck. Diagram 0 should include only forms, screens, reports, and records. ![]() The data dictionary is then modified to include the new structural records and elements gleaned from further interviews, observation, and document analysis.Įach level of a data flow diagram should use data appropriate for the level. Typically, these entries consist of the data flow names found on the data flow diagram and their corresponding data structures.Īfter conducting several additional interviews with users to learn the details of the system and the ways they interact with it, the analyst will expand the data flow diagram and create the child diagrams. For instance, the analyst may create a Diagram 0 data flow after the first few interviews and, at the same time, make the preliminary data dictionary entries. ![]() The use of algebraic notation and structural records allows the analyst to develop the data dictionary and the data flow diagrams using a top-down approach. Data dictionary entries may be created after the data flow diagram has been completed, or they may be constructed as the data flow diagram is being developed. ![]()
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