In-class Exercise BSAD 141 Entity/Activity Table, Context Diagram, Physical DFD exercise

Transcription

1 In-class Exercise BSAD 141 Entity/Activity Table, Context Diagram, Physical DFD exercise 1. Using the entity/ activity table, identify information /data processing activities (put a check next to the row number on the left), OR at least be able to separate the internal entities from the external entities 2. Identify all data flows 3. Draw a context diagram, and 4. Draw the physical DFD ADVICE: Model the process EXACTLY as it is described. Do not read anything extra into the problem. 1. Why do I need an entity / activity table? In practice these tables are not used, but are useful for teaching purposes: It is very helpful in separating internal entities from external entities. It is very easy to track data flows. It is a quick / easy way to organize information and to list out activities, flows, and entities. The table helps summarize information. 2. What is the difference between information processing (IP) activities and non-information processing (NIP) activities? IP activities involve action verbs associated with changing / transforming INFORMATION / data (See link to information processing activities from schedule). These activities indicate that data / information are being changed within the process being modeled. Any interaction with a data store is also an information processing activity. NIP activities represent information flows or information movement, or represent some type of operational activity such as driving to / from or constructing a building etc. NIP activities do not change or transform information / data. 3. Why do I need to differentiate between information processing (IP) activities and non-information processing (NIP) activities in the entity / activity table? It is helpful in identifying which entities are external to the system and which are internal to the system external entities vs- internal entities. External entities are outside the system being modeled and are represented by rectangles. External entities give some input to the system; receive some output from the system, or do both. They are not part of the process itself though. Internal entities are represented by NUMBERED process bubbles in the PHYSICAL DFD only. Internal entities do not appear in the context diagram or in the logical DFD. Internal entities are the people or things that actually change / transform the data / information within the process. You should be able to trace the information flows from external entities to specific internal entities and have new flows coming out of the internal entities. The exact same external entities are shown in the context diagram, the physical DFD, and the logical DFD they do not change and are consistent in all three diagrams. So, once you identify the external entities, you use them in all three diagrams. Internal entities do not represent the actual information changing activities (these will be represented in a separate diagram the logical DFD). Internal entities represent the people or things that perform the activities that change the information / data.

2 BSAD 141 In-class exercise Job Screening Process Entity / Activity Table Entity Activity 1 Junior HR Staff Receive application packet (resume, cover letter, references) from job applicants 2 Junior HR Staff Screen applications for completeness 3 Junior HR Staff If complete, store applications in application file (file cabinet) 4 Junior HR Staff Throw incomplete applications into trash 5 Junior HR Staff If incomplete, notify applicants by letter that they are no longer being considered for position 6 Senior HR Staff Retrieve complete applications from application file (file cabinet) 7 Senior HR Staff Sort applications into groups based on job position 8 Senior HR Staff Perform grade-based screening which involves separating applications with GPAs < 2.7 from those with GPAs >= Senior HR Staff Throw applications with GPA < 2.7 into trash 10 Senior HR Staff Send rejection to applicants whose GPA is too low (< 2.7) 11 Senior HR Staff Make copies of all applications with GPAs >= Senior HR Staff Update application file by placing a copy of all application packets with GPA >= 2.7 into application file 13 Senior HR Staff Forward sorted and screened paper applications to HR Director 14 HR Director Perform detailed final review of applications (involves checking references, verifying degree, etc). This activity involves some type of separating and organizing. 15 HR Director As part of review, make a phone call to the references listed in the application packet requesting personal information 16 HR Director As part of review, receive an official academic transcript from a university (in this case don t need the exact university) 17 HR Director Forward reviewed accounting applications to 18 HR Director Forward reviewed finance applications to Finance

3 Bold / highlighted information processing activities that involve any of the following: 1) Any activity that transforms, manipulates, changes information in ANY way (including changing the form of the data from electronic to print or producing additional instances of the data like copying). Look for non-transport related tasks like sorting, screening, processing, reviewing, etc. 2) Retrieving information from or placing information into a data store. 3) Updating a data store. Red external entities not involved in any information processing activities, but interact with the system in some way are EXTERNAL to the system. These are the entities that are sending input to the system and / or receiving output from the system. They are not part of the actual job applicant screening process. Internal Entities [1.0] Junior HR Staff [2.0] Senior HR Staff [3.0] HR Director External Entities Job Applicant Finance Trash (source / sink) References University Data Store File (file cabinet)

4 1. How can Finance and managers be external entities since they clearly work for the organization being modeled? Organizations have many different internal processes. The process we are looking at in this example is the Screening Process and it is performed by staff in the HR Dept. With respect to the collection, screening, and storing of applications, the managers are external to THIS process. Here we are not looking at the job candidate interview process itself or the hiring selection process. The managers would certainly be part of those processes. Here, the managers only receive output from the application screening process. They may use that output to perform other processes, but those are other processes and we are not concerned with them in the context of THIS problem. 2. Can trash be a data store? While I don t think I would count this as wrong on a test, technically treating trash as a data store is incorrect. Trash is better modeled as an external entity in the context of this problem. The organization is not storing data in the trash it is going to be thrown out, not retrieved for later use. Trash is an information sink not a place to store information for later use. 3. Do physical processes (the internal entities) need to be numbered? Yes. It provides some logical / sequential structure to data flows. 4. How can I tell a flow from an activity? There is not an exact algorithm for this. In the entity / activity table, any NIP (non-information processing not bolded here) activity is very likely a flow representing the physical movement of some data / information. IP (information processing bolded) activities are generally NOT flows, but represent some activity that changes / transforms data. These activities (correctly grouped and labeled) will end up forming the processes for the logical DFD. THE EXCEPTIONS are data flows to / from data stores, since interactions with data stores are IP. So, an IP activity from the table can be a flow if it is going to or coming from a data store. In general, you want to ask yourself what information is coming to the internal entity? From whom / where? What information is being generated by the internal entity? Where is this information going? 5. Do I have to indicate the form (paper / electronic / phone, etc) on the flow labels? Yes. And, you should clearly label flows with NOUNs. What exactly are the data being transferred? 6. What is the difference between the Context, the Physical, and the Logical Diagrams? You are not going to draw Logical diagrams, but they addresses the details of the activities inside the system like screening applications for completeness, screening applications based on GPA, performing a final review, etc. The Context diagram provides an overview of the ENTIRE system and the flows coming into the system and going out of the system. The Physical diagram builds upon the Context diagram by providing detail about who is involved in the system and how information flows between those people / things. 7. Why is there no transcript request coming from the process to University or no reference information being sent from References to the process? They are not included because I did not explicitly state this in the table or narrative. You are assuming these flows in this case. For the test I would not count this wrong. The point of the Physical DFD is to clearly identify the entities (both internal and external) involved in the process, clearly identify any data stores involved in the process, and to clearly show the information that flows between these things (and how it flows). Someone who is not familiar with the process should be able to pick up your DFD and understand who is involved and what data are being transferred.

5 CONTEXT DIAGRAM Job Applicant Notification Letter (incomplete ) Paper Packet (resume, application, references) Rejection (low GPA) Reviewed Paper s Applicant Selection Process Packets < 2.7 Incomplete Packets Trash Finance Reviewed Paper Finance s Reference Verification Phone Call Official Academic Transcript (?) References University If you show a flow from the process to the University such as, Request for Transcript (phone, paper, ), that would be fine. However, you would then need to include the same flow on the Physical DFD coming into the HR Director If you show a flow from References to the process such as, Applicant Reference Information (phone), that would be fine. However, you would then need to include the same flow on the Physical DFD coming into the HR Director

6 Note that the flow labels are very precise, do not include any action verbs (sending, receiving, etc.), and include the form of the data/information Physical Diagram Job Applicant Note that the Physical DFD is balanced with the Context diagram the external entities and flows to and from those entities are exactly the same in both Paper Packet (resume, application, references) Notification Letter (incomplete ) All internal entities / processes are numbered Rejection (low GPA) Incomplete Packets Trash 1.0 Junior HR Staff Complete Paper Packets Complete Paper Packets File (File Cabinet) Packets < 2.7 GPA 2.0 Senior HR Staff Copy of screened And sorted Packets (paper) Original paper Screened (GPA) and Sorted (position) Packets Reviewed Paper s 3.0 HR Director Official Academic Transcript (?) University Finance Reviewed Paper Finance s Reference Verification Phone Call References