طالبه مساعدة مشرف القسم والأعضاء الكرام وشكرا لكم
بسم الله الرحمن الرحيم
عندي شؤال صعب في مادة نظم المعلومات المحاسبية ومو عارفه حله ممكن تساعدوني في حله لأن تسليمه يوم الإتنين
والسؤال هو بالإنجليزي
The eTMA system
The eTMA system allows students to submit their answers to tutor-marked assignments (TMAs)
electronically, as computer files, to the University via a website. Whenever a TMA file is
submitted, it is stored in a central database and a ‘receipt’ (a simple message containing a unique
number) is sent to the student to acknowledge that the TMA has been received. Tutors (Associate
Lecturers) are informed, by email, that a TMA is waiting for them to be marked.
The system enables tutors to download their students' submissions, mark and comment on the
assignments ‘on-screen’ and submit the marked TMAs back to the University. A marked TMA is
stored in a database and the student is informed, by email, that their TMA has been marked and is
available to be retrieved electronically.
When the tutor downloads an unmarked TMA, she also receives an electronic version of the PT3
form on which the marks awarded for each question and the overall comments on the TMA must
be entered. The completed PT3 form accompanies the TMA when it is sent to the OU database,
and eventually both of them are sent electronically to the student.
The data flow diagram given in Figure 1 summarises the basic system.
Figure 1 The basic electronic tutor-marked assignment system
Whilst not shown in Figure 1, the fact that both the unmarked and marked assignments are saved
by the University enables it to implement a number of web-based reports that provide summary
information to students and tutors on the current status of their assignments within the system, as
well as providing management information for the University's Assignment Handling Office.
To match the existing paper-based TMA system, marks and tutor comments are extracted from
marked assignments and added to the students' records. Since the number and size of eTMAs is
potentially huge, the University has decided that complete marked and unmarked assignments
would be stored only for a short period of time.
From the start, the aim was to provide a web browser interface for both students and tutors.
However, for security reasons, there would be two subsystems: one for students and one for
tutors.
Should the eTMA system ever fail and be unavailable to students, a back-up system has been
implemented in which students are able to submit an assignment as an attachment to an email.
The attachment is extracted by the University and fed into the eTMA system once the eTMA
system is operational again.
The basic system has been gradually enhanced and now provides a number of facilities not shown
in Figure 1. For example, one of the OU's quality control systems involves monitoring, that is,
examining samples of each tutor's work to ensure that standards of marking are being maintained.
In the paper-based TMA system, clerks in the central Assignment Handling Office take samples
of marked TMAs, photocopy them, and send the copies to the monitors (academic staff who
review the work of tutors and report back on the quality of the work). In the current version of the
eTMA system, electronic copies of the tutors’ work are sent to the monitors who will send back
electronic versions of their reports.
The eTMA system also checks a number of business rules regarding the submission of TMAs.
For example, a student can make as many submissions as he likes, but only the last one will be
marked (provided the submissions are made before the cut-off date or before the tutor has
downloaded the eTMA).
The system also rejects any submission that either contains a virus or istoo large.
The description inside each process bubble should be as terse and as meaningful as possible. The
use of an imperative verb and a simple object can easily indicate the desired transformation. In
the
Case Study above for example, you can find processes called ‘Submit assignment’ and
‘Download unmarked assignment’.
It is common to use a decimal numbering system to identify each process or activity at its given
level of abstraction. For example, in Figure 1, we could label the six process bubbles from 1 to 6
with ‘Submit assignment’ being number 1, say. Then, if we wanted to show the details of ‘Submit
assignment’ in another DFD we would label the processes in the new diagram 1.1,1.2, and so on
to show the connection with the original DFD.
When you decompose or refine an activity and show the result in a new DFD it is essential, for
the development of a consistent set of models, that the inputs and outputs of each successive
decomposition or refinement remain the same. In addition to the set of DFDs that describe
something like the eTMA system, you should also prepare a dictionary or glossary of the terms
you have used in the diagrams like ‘assignment’ and ‘tutor identifier’. In particular, you need to
record your understanding of the content of the data associated with each arrow and the stores.
An important aspect of a DFD, and its main benefit in a requirements process, is that there is no
explicit indication of the sequence of processing in the notation. A DFD identifies what is
happening and what is being passed in and out of each activity, but it does
not specify the order in
which things happen. In other words, you can identify the activities that take place at a given
level of abstraction, such as Figure 1 above, but some other technique is needed to indicate the
time-ordering of those activities. Some kind of sequence
may be implied by the naming of
activities, as in Figure 1, although any combination of the activities may be somewhere between
their starting and finishing points at a given point in time.
The convention followed in DFDs to minimise the number of overlapping lines is to allow
external entities and data stores to be duplicated.
1. Draw a rough picture of the current system - showing the sequence of events.
2. Can you draw a DFD based on your understanding?
03-26-2010, 07:11 AM
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