Data Flow Diagrams and Software Inspection Standards

Data Flow Diagrams (DFD)

Data flow diagrams (DFD) are used to model system components, including processes, data entities, and the relationships between them.

Elements of a DFD

External Entities

These elements produce and consume system information without belonging to the system itself. They are represented by a rectangle.

Rules for External Entities

• All must be named.
• No relationship between them should appear outside the system.
• All must appear on the first-level DFD (context diagram), but may appear at lower levels for greater readability.

Processes

Processes represent functions or procedures that conduct an information system, transforming information during system performance. They are represented by a circle.

Rules for Processes

• All must have a name and a unique number.
• They must respect the principle of data retention.
• All data that goes in must come out; data cannot be created from scratch (not invented).

Data Storage

These represent elements for the temporary storage of system information. They are represented by two parallel lines.

Rules for Data Stores

• Each must have a unique name.
• They appear first at the highest level when connecting two or more processes.
• If used by only one process, it is considered local to that process and only appears when that process is exploded (split into more processes).
• Once they appear in DFDs, they can be used whenever necessary. Stores can be simple structures (record type) or complex structures (databases).

Data Flows

These represent the path that information follows through the information system (IS) via processes. They are represented by:

• Single arrow: For discrete flows (movement of data at a given time).
• Double arrow: For continuous flows (movements persistent over time), such as database updates.

Software Inspection Standards

For a successful inspection, the following rules must be followed:

1. Inspections are conducted during both the planning and development processes.
2. Inspect all types of possible defects.
3. The inspection involves all levels of company management.
4. Inspections should be conducted in strict stages.
5. Meeting time should not exceed two hours.
6. Inspections must be led by experienced moderators to ensure effectiveness.
7. Inspection team members should be assigned specific roles to increase efficiency.
8. Use checklists to manage member assignments.
9. Inspect the product with maximum focus on defect discovery.
10. File all statistics obtained for further analysis.