System Modeling: Context, Interaction, Structural, and Behavioral Models, Cheat Sheet of Introduction to Software Engineering

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Chapter 5 – System Modeling Week 3

Topics covered ▪ Context models ▪ Interaction models ▪ Structural models ▪ Behavioral models ▪ Model-driven engineering

System perspectives ▪ An external perspective, where you model the context or environment of the system. ▪ An interaction perspective, where you model the interactions between a system and its environment, or between the components of a system. ▪ A structural perspective, where you model the organization of a system or the structure of the data that is processed by the system. ▪ A behavioral perspective, where you model the dynamic behavior of the system and how it responds to events.

UML diagram types ▪ Activity diagrams , which show the activities involved in a process or in data processing. ▪ Use case diagrams , which show the interactions between a system and its environment. ▪ Sequence diagrams , which show interactions between actors and the system and between system components. ▪ Class diagrams , which show the object classes in the system and the associations between these classes. ▪ State diagrams , which show how the system reacts to internal and external events.

Context models

Context models ▪ Context models are used to illustrate the operational context of a system - they show what lies outside the system boundaries. ▪ Social and organisational concerns may affect the decision on where to position system boundaries. ▪ Architectural models show the system and its relationship with other systems.

The context of the Mentcare system

Process perspective ▪ Context models simply show the other systems in the environment, not how the system being developed is used in that environment. ▪ Process models reveal how the system being developed is used in broader business processes. ▪ UML activity diagrams may be used to define business process models.

Interaction models

Interaction models ▪ Modeling user interaction is important as it helps to identify user requirements. ▪ Modeling system-to-system interaction highlights the communication problems that may arise. ▪ Modeling component interaction helps us understand if a proposed system structure is likely to deliver the required system performance and dependability. ▪ Use case diagrams and sequence diagrams may be used for interaction modelling.

Transfer-data use case A use case in the Mentcare system

Tabular description of the ‘Transfer data’ use- case MHC-PMS: Transfer data Actors Medical receptionist, patient records system (PRS) Description A receptionist may transfer data from the Mentcase system to a general patient record database that is maintained by a health authority. The information transferred may either be updated personal information (address, phone number, etc.) or a summary of the patient’s diagnosis and treatment. Data Patient’s personal information, treatment summary Stimulus User command issued by medical receptionist Response Confirmation that PRS has been updated Comments The receptionist must have appropriate security permissions to access the patient information and the PRS.

Sequence diagrams ▪ Sequence diagrams are part of the UML and are used to model the interactions between the actors and the objects within a system. ▪ A sequence diagram shows the sequence of interactions that take place during a particular use case or use case instance. ▪ The objects and actors involved are listed along the top of the diagram, with a dotted line drawn vertically from these. ▪ Interactions between objects are indicated by annotated arrows.

Sequence diagram for View patient information