Graphs

• Graphs are an important mathematical and computer science concept.
• A graph consists of nodes and arcs that connect them.
• Graphs aren't going to be on the exam, but we use a couple of types of graphs for knowledge representation.
• We use semantic nets, decision trees, and-or trees, and frames.
• You probably also know about a few other types of graphs like entity-relationship diagrams, flowcharts, and case diagrams.
• Draw a graph!
• The key difference between types is that the nodes and arcs have different restrictions and meanings.
• For example, nodes in a semantic net represent concepts, the arcs are directed, the arcs are labelled, and they show the relationship between the nodes they connect.
• The nodes in a decision tree represent a question, and the the arcs represent answers.
• I'll show you a semantic net and a decision tree.