Logical System Models

4.2 Logical System Models

System models are techniques used to understand user needs and software engineer use these techniques in order to understand business domain. Software engineers develop diagrams to model different business  processes. System models include the following

• User business processes
• User activities for conducting the business processes
• Processes that need to be automated
• Processes which are not to be automated

Business process model

The first model that we will look at is called the process model. This model provides a  high-level pictorial view of the business process. This model can be used as a starting point in  giving the basic orientation to the reader of the document. Following is an example of a hospital  registration system which deals with two types of patients.

Business Process Model - Click to Enlarge

As opposed to flow charts, there are parallel activities in this diagram which are further
elaborated by specifying their major activities. The process described in this diagram is as
follows

• A patient may come to visit In Patient Department (IPD) or output patient department (OPD)
• System determines if he is a company patient or a private patient.
• For a company patient, system verifies him.
• For an OPD patient, system will issue a chit to the patient and inform him about his number and the consultant to whom he has to consult and he will have to wait for his turn.
• After verifying an IPD patient, system will create a visit and allocate him a room or a bed etc. If  system cannot allocate this, then it will inform the patient. Otherwise the patient is checked in and his information is maintained in the system
• System displays information about the expenses of the required service to the patient so that he is  informed of his expected expenditure. Some advance payment is also received against the required  service and this amount is adjusted in the final settlement.
• All this information is supplied to cash office that eventually deals with payments, etc.
• Upon receiving the cash, for OPD patient, a chit will be issued. For IPD patient, an admission form will be filled and this information will be maintained in the system. A receipt will be issued to the patient.
• For credit transaction, corresponding voucher will be prepared.
• So the model depicts process before the start of the treatment.
• A patient may ask to change his service on event of an unsatisfied response from the hospital staff or  any other reason. System may cancel his record and pay his amount back.
• Similarly, a doctor may ask a patient to change his status from OPD to IPD.

In a business process diagram, following points are important and should be noted

• It does not describe the automated system
• It only reflects the existing process of the user to help software engineer/analyst in understanding business domain.
• It may contain information on processes that need not be automated

Our next post will be State Transition Diagrams.