# Low Level Design
All Low Level Design notes →1 — UML Fundamentals
The UML notation vocabulary — classes, interfaces, relationships, visibility, and multiplicity — needed to read or draw any diagram in this Part.
2 — Class Diagrams
How class diagrams capture a design's static structure — classes, attributes, methods, and the relationships between them — before any code gets written.
3 — Sequence Diagrams
How sequence diagrams trace the message flow between objects over time to check that a design actually satisfies a use case.
4 — State Diagrams
How state diagrams model an object's lifecycle as a finite set of states and transitions, useful for anything with a status field.
5 — Activity Diagrams
How activity diagrams map the control flow and branching logic of a workflow or business process, independent of any single class.
6 — Object Diagrams
How object diagrams snapshot a specific set of instances and their links at a point in time, useful for validating a class diagram against a concrete scenario.
7 — Package Diagrams
How package diagrams organize classes into higher-level modules and show the dependencies between them, the tool for reasoning about a design's overall structure.