Reading Technique for Structured Analysis
Use the procedure below to perform a structured analysis of the new system by creating a data
flow diagram. As you work, use the questions provided to identify faults in the requirements:
1) Read through the requirements once, and then create a high-level data flow diagram. The
purpose of this diagram is to clarify the system’s relationship with the outside world.
Identify the data sources, destinations, and stores. Then describe the processing and specify
the data flows.
a) Data sources and destinations are anything outside the system that originate new data or
receive finished data. A source or destination could be, for example, an external system
that sends or receives messages, or a department or individual that will use the system to
be built. Destinations and sources are represented by closed boxes on the data flow
diagram. Label as many destinations or sources as necessary on Form A.
b) Data stores represent any data or documents that are stored for any length of time. This
might be, for example, a pile of papers making up a file, a database on CD-ROM, or any
kind of file which can be read from and written to. Data stores are represented as boxes
with one side missing. Show all of the external data stores by labeling the data store
symbols on Form A.
c) Boxes with rounded corners are used to represent processes or activities. Again, no
distinction is made between activities which are carried out by the computer and those
which are performed by some other physical device, as long as the processing is part of
the system. Therefore a process symbol could refer to a person undertaking a process, a
computer automatically performing some data transformation, a mechanical automated
process, or any other method which achieves a required result or set of results. In the
high-level data flow diagram there is only one process node which summarizes the entire
process. Label the process node on Form A with a description that describes the purpose
of the system described by the requirements. You will use this process node as the input
to step 2.
d) Finally, the arrows in the diagram represent data flows. These arrows show the flow of
data from a source or data store to a process in which it is used, from process to process,
or from a process to a destination or data store. Label these arrows with the actual data
which is provided to the system by each of the sources and stores, or which the system
sends to the destinations and stores. As always, there are no distinctions due to the form
of the data.
Q1.1 From the general requirements or your knowledge of the domain, have all of
the necessary data sources, destinations, and stores been defined?
Q1.2 Can you identify what type of data is provided by or sent to each source,
destination, or store? Can the data types be defined (e.g. are the required
precision and units specified for the data)?
Q1.3 Do the requirements specify the correct source, destination, or store for each of
the data flows?
2) Iteratively deepen the current processing node by constructing more detailed data flow
diagrams.
a) If there is insufficient detail to construct a lower-level diagram, or if there is only one
data transformation or processing step that takes place, this process does not need to
have a more detailed diagram created for it.
b) Otherwise, use Form B to construct a lower-level data flow diagram for the current
processing node. First, record the name of the current node on the appropriate line in
