prioritizing work for the Physics Derivation Graph

Now that the website works, there are three candidate categories of work:

• Presentation -- how does the site look, e.g., tables, use of color. images,
• Functionality -- what features exist, e.g. step validation, manipulating the graphs, form entry
• Content -- what derivations, symbols, expressions are present

Of these three, content is most important with functionality being second. Functionality enables the workflow.

Within the category of "content," there are three sub-categories:

• Derivations
• Abstract syntax trees -- how symbols and operators relate within an expression
• Inference rules

Of those three, the derivations are the highest priority. Inference rules enable derivations. 

The parsing of expressions in support of step validation is nice to have but not vital.

Within the topic of derivations, there is a plethora of candidates to invest in. Priorities are

• subject scope diversity -- span all topics in Physics
• simplicity -- not too many steps, easy math
• interconnectedness with other topics