Graphs & representations
Define directed, undirected, weighted and simple graphs and choose representations that preserve the relation of interest.
Subject
Purpose
Networks of vertices and edges studied through paths, connectivity, trees, coloring, flows and structural invariants.
Structure
Definitions → structures → relations → proof → application
Graph theory provides a formal toolkit for connectivity and constraint problems while separating abstract graph properties from the domain that produced the network.
Define directed, undirected, weighted and simple graphs and choose representations that preserve the relation of interest.
Study reachability, components, cycles and cuts as structural properties governing movement and separation.
Use acyclic connected graphs to represent hierarchy and minimal connective structure.
Model allocation, conflict and transport constraints through reusable graph optimization problems.
Use matrices, degree patterns and other invariants to connect local structure with global graph behavior.
graph ≠ network data set
tree ≠ hierarchy in every sense
shortest path ≠ best route
Which graph representation preserves the mechanism being studied?
How do local degree patterns constrain global connectivity?
When does an optimization problem on a graph become computationally hard?
Proofs concern abstract graphs; applications need a separate justification that the real-world relation is encoded faithfully.