| (a) |
(i) What is meant by the term data
dictionary? |
[2] |
|
(ii) Draw and describe each of the five
symbols which may be found in a data dictionary. |
[5] |
|
(i) A data directory
is a repository which contains definitions of the data flows, processes, data stores, data
structures and data elements used in a set of data flow diagrams for a system. (ii)
| Symbol |
Meaning |
| + |
and |
| = |
is made up of |
| ( ) |
optional item is
enclosed within it. |
| { } |
iteration of item
enclosed within it. |
| [1] |
indicates a selection
of item from alternative choices separated by a '1'. |
|
|
| (b) |
(i) List three points which illustrate the
relationship between the data dictionary and the data flow diagram in a structured
specification. |
[3] |
|
(ii) List two differences between data flow
diagrams and structured flowcharts. |
[2] |
|
(i)
- There is one data dictionary entry
for each unique data flow in DFD.
- There is one data dictionary entry
for each unique functional primitive process.
- There is one data dictionary entry
for each data store in the Data Flow Diagram.
(ii)
| DFD |
Structured flowchart |
| Indicate data flow |
Does not indicate data
flow |
| Indicates parallel
activities |
Indicates only
sequential activities |
|
|
| (c) |
A development team has recently finished its
analysis of a current system. However, the analyst preparing the data flow diagram is
inexperienced and has made several mistakes. Identify each of the errors in the diagram
below. 
|
[8] |
|
The errors are:
- The data flow from process 1 to 2 is
not labeled.
- The data store 'orders' is not a
duplicate entity since there's no identical data store in the DFD.
- The external entity 'customer', is
not a duplicate entity as only one customer entity appears.
- Direct data flow between two
entities (customer & subsidiary) is not permitted. A process should be introduced
between the 2 entities.
- The process 'File invoices' is not
numbered. IT should be numbered as '4'.
- The portion of the DFD indicated
above is completely disjointed from the rest of the DFD.
- 'Management' should be depicted as
an entity instead of a process.
- For the process, Evaluate, process
is not properly labeled. It should be labeled with a strong verb and noun. e.g Evaluate
orders.
|
|