I have gone and looked at the various software development diagrams available on Wikipedia. I have focused on the graphs (nodes and connections). The natural level for graphs is level 4 (knowledge representation and ontologies). However level 4 has a broader scope than just (K.R. and O.). Here is what I was able to suss out.

Level 4 – High Level Information Programming – Knowledge Representation

Level 4 proper diagrams mostly have to do with relationships.

• Anchor modeling
• Concept map
• Conceptual graph
• Conceptual model
• Concept-oriented model
• Context diagrams
• Data flow diagram – this diagram has a long and storied history, As level 4 develops, I expect to see this diagram rise in importance again.
• Domain model
• EXPRESS-G
• Information flow diagram
• Information model
• Object model
• Object-role modeling
• Semantic network
• Semantic Web
• Top Level Ontology

Some level 4 proper diagrams are based more on hierarchies than relationships. Of course a hierarchy is a kind of relationship.

• Argument map
• Cladistics
• Document Object Model

Level 4 for Other levels

Here are some level 4 diagrams that apply to other levels:

• 4(5) Fuzzy cognitive map

• 4(3) Nets within Nets
• 4(3) Specification and Description Language
• 4(3) Composite Structure Diagram (UML)

• 4(2) Abstract syntax tree
• 4(2) Class diagram (UML)
• 4(2) LePUS3
• 4(2) Tree structure

• 4(1) Entity–relationship model
• 4(1) Hierarchical database model
• 4(1) Network model

Diagrams for Other Levels

Here are diagrams that apply directly to other levels, although one could
certainly build systems at level 4 that would process these.

Level 1 – Data Storage and Relational Databases

Level 1 isn’t really very diagrammatic. It mostly relies on grids. The diagrams that apply best seem to be level 4 diagrams that manage level 1 such as entity relationship diagrams.

• Jackson structured programming
• Symbol table

Level 2 – Data and Object Oriented Programming

Many of these diagrams have to do with various sorts of process flow.

• Algebraic Petri net
• Behavior tree
• Business process mapping
• Business process model
• Control flow diagram
• Decision tree
• Directed acyclic graph
• DRAKON diagram
• Dynamic model
• Enhanced Transition Schematic
• Event-driven process chain
• Finite-state machine
• Flowchart
• Flow process chart
• Function model
• Interaction overview diagram (UML)
• Petri net
• Sequence diagram (UML)
• State diagram (UML)
• State Machine
• Use Case Diagram (UML)

Level 3 – Low Level Information Programming

I have had a lot of trouble trying to find any diagrams that apply to level 3.
These are the closest, but they are very thin gruel.

• Activity diagram (UML)
• Composite structure diagram
• Business logic
• Component diagram (UML)

Level 5 – Artificial Intelligence

Knowledge representation is a substrate for artificial intelligence. I expected to find more of these. Perhaps as level 4 develops there will be more in the future.

• C-K theory
• Extended Enterprise Modeling Language

Level 6 – Computational Creativity

Computational Creativity is a severely underdeveloped level. I didn’t expect to find anything, but here is one that may make sense.

• Mind map