Flow oriented Modeling - Creating a Control Flow Diagram and The Control Specification

Flow models focus on the flow of data objects as they are transformed by processing functions. There are applications which are driven by events rather than data and produce information that is controlled and process information keeping in mind the time and performance. In such situations, control flow diagrams comes into picture along with data flow modeling.

There are some guidelines to select potential events for a control flow diagram:
- all sensors that are read by the software are listed.
- all interrupt conditions are listed.
- all switches actuated by operator are listed.
- all data conditions are listed.
- all control items are reviewed.
- all states that describe the behavior of a system are listed.
- all transitions between states are defined.
- all possible omissions should be kept in focus.

The Control Specification contains a state diagram which is sequential specification of behavior. It contains a program activation table which is a combinatorial specification of behavior. Control specification does not give any information about the inner working of the processes activated as a result of this behavior.

Flow Oriented Modeling - Creating a Data Flow Model

Flow models focus on the flow of data objects as they are transformed by processing functions. Derived from structured analysis,flow models use the data flow diagram, a modeling notation that depicts how input is transformed into output as data objects move through the system. Each software function that transforms data is described by a process specification or narrative. In addition to data flow, this modeling element also depicts control flow.

Data flow oriented modeling is the most widely used analysis notation. Flow oriented modeling focuses on structured analysis and design, follows a top to down methodology and uses a graphical technique depicting information flows and the transformations that are applied as data moves from input to output.

The modeling tools that are used to build a data flow oriented model include context diagrams, data flow diagrams, entity relationship diagram, control flow diagram, state transition diagram, data dictionary, process specification and control specification.

Steps to create a data flow model
- Diagram 0: develop a context diagram.
- Decompose the Process into high level processes.
- In parallel to this, develop data flow diagrams, entity relationship diagrams and state transition diagrams.
- Define data stores which includes normalization.
- Develop data dictionary.
- Finalize data flow diagrams, entity relationship diagram and state transition diagrams.
- Develop process specifications which includes PDL, decision tables or trees.
- Perform transformational analysis which includes developing structure charts.
Information flow continuity must be maintained as each data flow diagram level is refined. This means that input and output at one level must be the same as input and output at a refined level.