MILESTONE 5 – PROCESS MODELING – Part II (Exploded DFD)
1. Level 0 Data flow Diagram
he requirements analysis phase answers the question, ‘What does the user need and want from a new system?’ The requirements analysis phase is critical to the success of any new information system! In this milestone we need to identify what information systems requirements need to be defined from the system users’ perspectives.
The Data Flow Diagram (DFD) is a graphical representation of system which shows systems structure and components. The DFD shows how the data transforms in the system, what the source of the input is and what is the destination. Also, the DFD presents data structure and how it’s stored.
In this milestone you will explode the Context level DFD to Level 0 DFD to show sub-systems (processes). The Level 0 DFD shows internal data stores and how data flows through the processes.
2. Child diagram definition
hild level diagrams show details and are built till needed level of details is reached. First, we show the information system as a single process on the Context diagram. Then, we decompose and show more details until all processes are functional primitives. Not all processes are exploded to the same number of levels- it’s not required to explode all processes to the same level. The main target is to reach the functional primitive which will be translated into units of program code.
After completing this milestone, you should be able to:
- Create a Level 0 (System) Data Flow Diagram
- Create a Child Data Flow Diagram
Before starting this milestone, the following topics should be covered:
• Process Modeling – Chapter 9
As a systems analyst or knowledgeable end-user, you must learn how to draw data flow diagrams to model business process requirements. The preliminary investigation and problem analysis phases of the methodology have been completed and you understand the current system’s strengths, weaknesses, limitations, problems, opportunities, and constraints. You have already built the Context models (Milestone 3) to document business requirements for the new system. You now need to build the Level 0 (System) DFD and corresponding process models.
- Develop Level 0 DFD. Make assumptions where necessary.
- Draw one Child Diagram using the Level 0 diagram.
- Continue decomposition of one process up to primitive processes (Level 2, Level 3, etc.)
Deliverable format and software to be used are according to your instructor’s specifications. Deliverables should be neatly packaged in a binder, separated with a tab divider labeled “Milestone 5-Part II”.
• Context Data Flow Diagram Narrative – Exhibit 5.1
Level 0 Data flow Diagram
Child level diagrams: Due: __/__/__
Advanced option is to develop Child diagrams for all processes in Level 0 DFD.
Child level diagrams: Due: __/__/__
Milestone’s Point Value: ____
The following is a copy of the transcript of an interview you, a systems analyst from Information Systems Services (ISS), conducted with Oscar Barrett, Janine Peck, and S.P. Marsh of the Equipment Depot. The goal of this interview was to determine requirements for the proposed system.
Scene: The Equipment Depot. You have scheduled to meet with the Equipment Depot staff just after the 3:00 PM shift change when Oscar Barrett finishes work and Janine Peck starts her shift. S.P. Marsh, the third shift employee has agreed to come in for the meeting.
You: Well, here we all are again. I promise you I won’t be meeting with you to death.
Oscar: That’s OK. We want to help make sure the system does what we need.
You: Good. That is really my goal for this meeting. I want to get consensus on
everything the Equipment Check-Out System needs to do and who will be using
each parts of that functionality. I already know the basic functions for the system.
Employees need to check-out equipment and check it back in. But I was
wondering if you envisioned you doing the data entry or employees?
Oscar: We were talking about that. We are thinking of having two terminals here and
letting employees do their own check-outs with the system verifying the skill
classification and the equipment availability. It will generate a receipt they’ll
bring to us so we can actually fetch the tool. But we’ll have to check-in to verify
that they are actually bringing the tool back. That would speed us up.
You: Sound good. Now what if the employee loses the equipment he or she checks out?
Janine: That’s a real pain. Sometimes employees report that they lost something. But
more often than not they don’t report it, hoping they’ll find it in a few days.
You: So if they do report it, do you do anything?
S.P.: Not initially. If someone needs that equipment and it is still lost, we may have to
purchase a new one. In that case we try to mark the original check-out slip with a
note of the lost and the cost of the replacement.
Janine: We do the same thing if employees checks in equipment they have damaged. We
send it out for repair and mark the original check-out slip – if we can find it. But
you’re going to solve all our finding problems, right?
You: I’ll do my best. What about when lost equipment is later found?
Oscar: Conceptually, it’s the same as a check-in, assuming we can match it with a check-
out. Actually, a little more goes on. If a replacement has been ordered because of
the loss, we erase it.
S.P.: I say we shouldn’t erase it. The replacement is an expense the company wouldn’t
have had if the employee hadn’t lost the equipment in the first place.
Oscar: Dan Stantz is in the process of making a ruling on that. With this new system
we’ll actually be able to monitor employee losses for the first time, so now we’re
thinking through the issues.
You: I think I see a loophole. If an employee loses or steals equipment and never
reports it and no one notices a need to order a replacement, then you don’t have
any way to identify that as a loss.
Janine: You’re right. We were just discussing that the other day. The solution we came
up with was that we should generate a report of equipment checked-out for more
than 30 days. Then we’ll contact the supervisors and have them check it out.
You: That brings up another question I had. I think you also wanted a procedure to
locate who had a specific piece of equipment?
Oscar: That would save us loads of time.
You: OK. Now I need to ask about the skill classifications. What are all the events
related to that?
Oscar: OK. The Safety Committee meets periodically sends us what’s called a
Restriction Notice. It just specifies the allowable skill classifications for each
piece of equipment. When a new employee is hired, the supervisor makes a skill
classification determination and communicates that to us as well.
S.P.: And sometimes employees get their skill classifications upgraded. Supervisors
then send us notice of that as well.
You: And what you do in setting the skill classification for a new employee is
essentially the same as changing the skill classification for an existing employee?
Janine: That’s right. And don’t forget that we have to take employees out of the system
when they quit or are fired.
You: Got it. Now what about purchases? You said last time that both you and
supervisor submit purchase requests and that you order equipment. Are those two
S.P.: Well, yeah.
You: Let me ask it this way: Do you track separate information on a request versus an
order or do different things?
S.P.: I see what you are asking. Yes, we need a reason for the request – whether it is a
replacement or a brand new kind of equipment for a specific job or whatever.
Then the order is a separate step.
You: Then after the order is placed?
Janine: As we said last time, right now we field calls from supervisors asking the status
of the order. We would like the system check the status.
You: I was wondering about that. You couldn’t just check the status through their web
S.P.: It gets really slow. I don’t know if it is our connection speed or something on their
web site. But if we could somehow download that status data, it would be great.
You: I’ll see what I can do in the nearest future. But their web site wouldn’t know when
an order actually comes in our door. So you’ll need some way to enter that
Oscar: I suppose it does. I think you are starting to understand this system.
You: Well, I hope some. Have we discussed everything the system needs to do?
Janine: We mentioned some other reports in our last meeting.
You: Right. I already have that information, so I won’t have to ask you about it again.
If you can’t think of anything else, then I think that is it for now. Thanks again for
Oscar: Hey, thank you.
S.P.: Yeah, thanks.
Janine: As you can see, we’re excited about this. Design fast.
Each process from primitive DFD may be developed as the individual module.
The software design technique which is based on the composing software from separate, interchangeable components is known as the module.
Modular design is a way to organize the complex system as a set of distinct components. Components may be developed, tested independently and then plugged together.
Modular design is supported by three types of logic:
– Decision making or control;
– Iteration or repetition.
Sequential – execution of steps one after another.
Decision making – execution of step depends on results of condition or set of conditions. Decision making is also called the selection or control.
Iteration – execution of steps is repeated until the specific condition changes. Iteration is also called as repetition or looping.
In this milestone you will write the Structured English for primitive process.
After completing this milestone, you should be able to:
- Write the Structured English for primitive process.
Before starting this milestone the following topics should be covered:
1. Child level DFD – Chapter 9
2. Physical level DFD – Chapter 9 and12
3. Structured English – Chapter 9
4. Fact-finding results – Chapter 6
The goal of this part of project is to write Structured English.
1. Write the Structured English for one-two primitive processes. Include sequential, decision making and iteration logics. Your instructor will indicate what specific processes to document.
Previous narratives and supplied forms
See on-line learning center website for the textbook.
Structured English: Due: __/__/__