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"Inference rules", "expressions", and "feeds" are words specific to the Physics Derivation Graph.
Represented graphically, their relation is
Read this directed graph as, "The inference rule acts on the input expression and, combined with the feed, produces the output expression." Inference rules can be considered as functions; the above picture would be
def inference_rule(input_expression, feed):
return output_expression
| word | definition | see more |
|---|---|---|
| Left-hand side # | LHS of an expression. LHS is comprised of non-relation symbols. In an expression, LHS is separated from RHS by a relation. |
|
| LHS # | See Left-hand side | |
| Right-hand side # | RHS of an expression. RHS is comprised of non-relation symbols. In an expression, RHS is separated from LHS by a relation. |
|
| RHS # | See Right-hand side | |
| Expression # | An expression is comprised of a LHS, relation, RHS
Expressions include both equations (the relation operator is equality) and inequalities (the relation operator is an inequality).
Each expression appears only once in the Physics Derivation Graph. |
list of expressions |
| Feed # | An inference rule may require one or more "feed" values.
A feed may appear more than once in the Physics Derivation Graph. A feed does not have a relation (e.g., equality or inequality). |
|
| Inference Rule # | Acts on one or more Expressions. Inference rule is the defining feature of a Step. |
Inference rules |
| Symbol # | "Symbols" refers to relations, operations, scalars, vectors, matrices. | |
| Operation # | Appears in LHS and RHS of an expression. Requires one or more arguments. | list of operations |
| Relation # | separates the LHS and RHS of an Expression. | list of relations |
| Derivation # | A derivation is comprised of steps. | list of derivations |
| Step # | A step is comprised of an inference rule and one or more expressions. | |
| value # | constants have numeric values with units. | |
| constant # | ||
| variable # | ||
| unit # | Constants are either unitless or have units. Each dimensionality has a set of units. |
|
| dimensionality # | Variables and constants are either dimensionless or have dimensionality. | |
| index of step # | Steps in a Derivation are ordered. | |
| index of input expression # | Expressions referenced by a step are ordered. | |
| index of feed expression # | Expressions referenced by a step are ordered. | |
| index of output expression # | Expressions referenced by a step are ordered. |