Chapter 10 - Analyzing Systems Using Data Dictionaries

1. Validate the data-flow diagram for completeness and accuracy.
2. Provide a starting point for developing screens and reports.
3. Determine the contents of dat stored in files.
4. Develop the logic for data-flow diagram processes.

1. Information about the data maintained by the system, including the data flow, data stores, record structures, and elements.
2. Procedural logic.
3. Screen and report design.
4. Data relationships, such as how one data structure is linked to another.
5. Project requirements and final system deliverables.
6. Project management information, such as delivery schedules, achievements, issues that need resolving, and project users.

Defining the Data Flow

1. Assign an ID.
2. Assign a unique descriptinve name.
3. Create a general description of the data flow.
4. Source of the data flow.
5. Destination of the data flow.
6. Type of data flow (file record, screen, report, form, internal)
7. Name of data structure in the data flow.
8. Volume of data.
9. Comments.

Describing Data Structures [notation] Fig. 10.5

• = "is composed of"
• + "and"
• {} repetitive elements
• [] either / or
• () optional element

Logical and Physical Data Structures

Data Elements

1. Element ID.
2. Element name.
3. Aliases.
4. Short description of element.
5. Base / Derived element?
6. Size of element.
7. Data type.
8. Input / Output formats.
9. Validation criteria.
10. Default values.
11. Comments.

Data Stores

1. Data Store ID.
2. Data Store name.
3. Alias.
4. Short description of the data store.
5. File type (manual / computerized).
6. File format (database vs. flat file).
7. Maximum and average # of records.
8. Data Set (File) Name.
9. Data strucure.
10. Primary and secondary keys.
11. Comments.

• Analyzing Input and Output
• Developing Data Stores

• All base elements on an output data flow must be present on an input data flow to the process producing the output. Base elements are keyed and should never be created by a process.
• A derived element must be created by a process and should be output from at least one process into which it is not input.
• The elements that are present on a data flow coming into or going out of a data store must be contained within the data store.