We continue with the GEMS system in the Maple Ridge Engineering case. Your tasks in Homework 3 are as follows:
1. (Worth 20% of the homework grade) Draw the level 1 data flow diagram (DFD) for GEMS process 2, Update Resources, which is the process that will create and update resource information for projects being tracked in GEMS.
Be sure to refer to the existing documentation about this process in Rabin's office
It may be helpful to look at existing DFDs and documentation for other GEMS "Update" processes
2. (25%) Draw the level 2 data flow diagram (DFD) for process 1.3, Update Tasks. GEMS process 1.3 will create and update task information for projects being tracked in GEMS. The hints from problem 1 also apply here.
3. (25%) For process 1, Update Project Information, add a new process (process 1.7) that will create and update the Deliverable data store. This data store will keep deliverable information for projects being tracked in GEMS.
The data store will contain the Deliverable Number, Deliverable Name, and Type of Deliverable (such as
software, equipment, and so on). Each Project must have one or many Deliverables, and each Deliverable must be for one Project. Process
1.7 should enable the user to enter the Deliverable information and then select the Project for the Deliverable. Complete both of the following:
a. Write a "Diagram Specification" for process 1.7, similar to what exists for processes 1.2-1.6
Hint: Follow the pattern established by the GEMS analysts in processes such as 1.3 and 1.4.
b. Draw only what will need to be added to the level 1 DFD for process 1 to depict process 1.7. You don't
need to show what already exists in the level 1 DFD for process 1.
4. (20%) Draw the level 2 DFD for the new process 1.7
5. (10%) Draw what will need to be added to the GEMS entity-relationship diagram (ERD) to address the data
requirements for process 1.7. You don't need to show what already exists in the GEMS ERD. Ensure consistency between process 1.7 data stores on the DFD and entities on the ERD (see Additional Guidelines for DFDs
section below)
Note: Use your tool of choice (e.g., Office, OmniGraffle (OS X), Visio, Visible Analyst, etc.). Ideally, you will submit a single document (e.g., pdf, Word, or equivalent) that includes your copy-and-pasted diagrams and other information,but I am flexible. The main thing I am looking for is that you are capable of creating the systems analysis documentation.
Additional Guidelines for Data Flow Diagrams (DFDs):
External Entities:
External people, systems
Reside outside the system, but interact with the system
May: a) receive information from the system, b) trigger the system into motion, or c) provide new
information to the system
Examples: Customers, Managers
Not clerks or other staff who simply move data
Data Stores:
Internal to the system. This means the system being modeled writes/transforms the data.
Internal data stores must have a process that writes data to them. If not, then possibly the data store is
external and it is not the responsibility of this system to manage this data store. External data stores are
modeled on DFDs as External Entities.
Internal data stores must have a process that reads their data. Else, why is the system storing the data in the first place?
The above two rules are probably the most frequently violated in students' models.
Ideally, every data store on your DFD should correspond to an entity on your ERD (this excludes technical data stores, e.g., journal records)
Data Flows:
Data in motion, such as:
From external entity (source) to the system
From the system to external entity (sink)
From internal symbol to internal symbol, but always originates and/or terminates at a process
Data flows moving into and out of data stores should reflect the internal structure of the data stores
Processes:
Always internal to the system
Follow the laws of conservation of data:
Data stays at rest unless moved by a process
Processes cannot consume or manufacture data
Must have at least 1 input data flow (i.e., no miracles)
Must have at least 1 output data flow (i.e., no black holes)
Should have sufficient inputs to create the outputs (i.e., no gray holes)
A process name should use the verb-adjective-noun format
DFD Balancing:
Information depicted on one DFD should be consistent with information depicted on lower level DFDs.