limiting my effort to just Latex for expressions

The core of the Physics Derivation graph is the relation between expressions. I've considered how much additional knowledge could be captured by storing expressions as Abstract Syntax Trees. While this would add a lot of work and therefore take more time, there's potentially a lot of value in having a more robust representation. Additionally, there's the challenge that I don't know how to represent all expressions in Physics using Abstract Syntax Trees.

Rather than store each expression as an AST, I'm going to limit my effort to just storing expressions using Latex. As a consequence, the validity of inference rules applied to expressions not be able to be checked. If someone comes up with a representation more useful than Latex (ie ASTs, MathML, etc), then a conversion will need to be performed.

The second reason the choice of Latex is significant because it limits how far down in the hierarchy that can be enumerated. Specifically, in the context of these layers

• Physics derivation graph
• Derivation 
• Step 
• Expressions, inference rules 
• Symbol, operators

the Physics Derivation Graph with Latex will not be able to explore systematically the symbols and operators used.