Exercise 2 9Mar 2012

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1.Students may enrol themselves for 1 or more courses. And a course can be
taken by 1 or more students.
2. There are 2 levels of courses. Level 1 is a course of 1 day and level 2 is a
course of 5 days.
3. The students will be divided in groups. So a student can be in 1 or more
groups and a group can consist of 1 or more students.
4. A Teacher can teach 1 or more courses but a course can only be given by 1
teacher.
5. The course will end with an exam.
6. Students can take the exam only if they attend on the minimum required
days of the course. If a student takes a level 1 course, they must attend 1 day
of the course. If a student takes a level 2 course, they must attend the course
for a minimum of 3 days.
7. Students that pass the exam receive an diploma.
1.
Develop a physical DFD that models the process of grocery shopping from the time
you write down a shopping list until the time you store purchased groceries in your
home. Construct your DFD as a linear sequence of processes. Now develop a
logical DFD to describe the same scenario. Try to develop a diagram that is equally
valid as a logical description of the way you currently buy groceries and as a logical
description of ways you might buy groceries without ever leaving your home.
Note that process names on the physical DFD all note the person performing the
process. Note also that the customer is represented as both an external entity and as
two processes. All of the processes are performed in a linear sequence.
In contrast, the logical DFD omits all references to persons performing processes.
The customer’s needs/preferences are now represented in an explicit data store (Stock
List) instead of within the logic of the Select Groceries process. An extra process has
been added to maintain the new data store. Some of the old processes are now
performed in parallel as a result of separating the physical groceries from their
information content.
English.
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