Software Engineering Week 3 High Level Design (1) PDF

CP317A Software Engineering High-level design, part-2 – week 3-2 Shaun Gao, Ph.D., P.Eng. Agenda Review week 3 - 1 Race condition Unified modeling language (UML) UML diagrams Structure diagram - Class diagrams Behavior diagram – use case diagram, sta...

CP317A Software Engineering High-level design, part-2 – week 3-2 Shaun Gao, Ph.D., P.Eng. Agenda Review week 3 - 1 Race condition Unified modeling language (UML) UML diagrams Structure diagram - Class diagrams Behavior diagram – use case diagram, state transition diagrams, Sequence diagrams Design principles (3 principles) Decomposition (divide and conquer) Cohesion Coupling Summary Review week 3-1 Software Reliability Software security Concept User interface Concept Architecture design Monolithic Client/server Component-based Service-oriented Data-centric Event-driven Distributed Race condition Event-driven architecture or distributed architecture can cause race condition A race condition is an undesirable situation that occurs when more than one process attempt to modify the same object at the same time. What is the problem of a race condition? lost data consistency Prevention techniques: Mutual exclusion Semaphores Unified modeling language (UML) UML Definition: UML is a general-purpose, developmental, modeling language in the field of software engineering that is intended to provide a standard way to visualize the design of a system. Note: UML is not actually a single unified language. Instead, it defines several kinds of diagrams that is used to represent the system. UML version 2.0 defines 13 diagrams UML diagrams UML: Structure diagrams – cont. Structure diagram: A structure diagram is a diagram that show the static structure of the system and its parts on different abstraction and implementation levels and how they are related to each other. Examples: Class diagram … Exactly one - 1 Zero or one - 0..1 Many - 0..* or * One or more - 1..* UML: Structure diagrams – cont. Class diagram symbols UML: Structure diagrams – cont. Class diagram example UML: Structure diagrams – cont. Component diagram Component diagrams are used in modeling a system, which are used for visualizing, specifying, and documenting all possible components in a system. Examples: ATM UML: Behavior diagrams Behavior diagram: A behavior diagram is a diagram that show the dynamic behavior of the objects in a system, which can be described as a series of changes to the system over time. Examples: Use case diagram State machine diagram Sequence diagram Interaction diagram … UML: Behavior diagrams – cont. Use-case diagrams A use-case diagram is a diagram that consists of actors, use cases and their relationships among the actors and the use cases. The diagram is used to model the system/subsystem of an application. A single use case diagram captures a functionality of a system. Example: ATM UML: Behavior diagrams – cont. Use-case diagrams – cont. The purposes of use case diagrams: To gather the requirements of a system. To get an outside view of a system. Identify the external and internal factors influencing the system. Show the interaction among the requirements. UML: Behavior diagrams – cont. State machine/transition diagram A state transition diagram is a diagram that is used for modeling discrete behavior through finite state transitions. It describes the behavior of the system. It consists of states and events Examples: Automatic door system Operating systems TCP data communications UML: Behavior diagrams – cont. Sequence diagrams A sequence diagram is a diagram that shows object interactions arranged in time sequence. It depicts interactions between objects in a sequential order i.e. the order in which these interactions take place. It contains (1) objects, (2) interactions, (3) timeline. Think – Pair – Share Structure diagram Class diagrams Component diagrams Behavior diagram Use case diagram, State transition diagrams, Sequence diagrams For the group project, which diagram(s) can be used? And why? Design principle 1: decomposition Decomposition Decomposition is also known as factoring, is breaking a complex problem or system into parts that are easier to conceive, understand, program, build, and maintain. An example: ATM Design principle 2: Cohesion Cohesion Cohesion is a measure that defines the degree of intra-dependability among elements of a module. The greater the cohesion, the better the software design. Example: ATM Design principle 3: Coupling Coupling Coupling occurs when there are interdependencies between one component/module and another. When interdependencies exist, changes in one place will require changes somewhere else. The lower coupling the better software design Cohesion vs. Coupling Design principal summary Summary Race condition Unified modeling language (UML) UML diagrams Structure diagram - Class diagrams, component diagrams Behavior diagram – use case diagram, state transition diagrams, Sequence diagrams Design principles (3 principles) – also apply to detailed design Decomposition Cohesion Coupling Announcement Please start the group project from writing the project report (SDD) Please let me know if you need help for finding a group Low level design from next week