MN 113-8: Primmel Symbol Registry

1.1. General

The symbol registry provides typed, unit-aware formal symbol definitions with LaTeX rendering hints and normative traceability. Symbols are referenced from OCL expressions inside calculations and form evaluation rules.

1.2. Why symbols exist

Without a symbol registry, OCL expressions reference bare identifiers with no type checking, no unit validation, and no documentation hint. For technical standards with many symbols (OIML R 60 has ~50), this leads to:

• Typos that silently evaluate to null
• Unit mismatches that produce wrong results
• Documentation that drifts from the implementation
• No traceability from a symbol back to its normative definition

The symbol registry solves all four problems.

1.3. Relationship to other Primmel constructs

1.4. Identifier conventions

Symbol identifiers should match the printed standard's notation where possible. For Unicode-friendliness:

• Use ASCII letters and digits: f, nLC, Emax, MPE, C_C, C_DR
• Use underscore for subscripts that don't render well as plain letters: C_C, C_DR, C_M
• Reserve capitalization for quantities ( Emax, MPE); lowercase for variables ( f, n, p_LC)
• The latex property provides the formal rendering for documentation

2.1. General

A symbol declaration uses the symbol keyword followed by an identifier and a brace-delimited body.

2.2. Syntax

symbol <SymbolID> {
  name "Human-readable name"
  definition "Formal definition"
  type <SymbolType>
  unit "<unit>"
  latex "<LaTeX rendering>"
  reference { <ReferenceID> }
}

1. Display name. Required.
2. Formal definition. Optional but recommended.
3. Type: number, integer, string, boolean, or enum.
4. Unit annotation. Optional (dimensionless = ”1“).
5. LaTeX rendering hint for documentation. Optional.
6. Normative references. Optional.

2.3. Properties

2.4. Example: OIML R 60 symbols

symbol f {
  name "Conversion factor"
  definition "Ratio of indication change to load change at 75% of Max. Converts counts to verification units (v)."
  type number
  unit "counts/v"
  latex "f"
  reference { R60-3-2-1-2-4 }
}
symbol nLC {
  name "Maximum number of load cell verification intervals"
  definition "Declared by the manufacturer. Determines the MPE tier and run count."
  type integer
  unit "1"
  latex "n_{LC}"
  reference { R60-1-3-5-8 }
}
symbol Emax {
  name "Maximum capacity"
  definition "Upper bound of the measuring range."
  type number
  unit "kg"
  latex "E_{max}"
  reference { R60-1-3-3 }
}
symbol MPE {
  name "Maximum permissible error"
  definition "Tiered MPE values derived from p_LC and verification intervals."
  type number
  unit "v"
  latex "MPE"
  reference { R60-1-5-3-2 }
}

3.1. General

Symbols are typed. The type system is intentionally minimal — five primitives that cover virtually all compliance use cases.

3.2. Allowed types

3.3. Unit conventions

Units are free-form strings, but should follow SI conventions:

• kg, g, t — mass
• m, mm, μm — length
• s, min, h — time
• K, °C — temperature
• V — voltage
• A — current
• Ω — resistance
• % — percentage
• 1 — dimensionless (default)
• Compound: counts/v, kg/m³, m/s²

3.4. Unit compatibility

When a calculation input has a declared unit and a binding provides a different unit, the parser:

• Allows dimensionless coercion ( ” 1 “ ↔ any unit)
• Allows scale prefixes ( kg ↔ g with explicit conversion)
• Rejects incompatible units ( kg ↔ V)

3.5. Default unit

If no unit is declared, the default is ” 1 “ (dimensionless). Dimensionless values can be bound to any unit without explicit conversion.

3.6. Enum values

For type enum , declare allowed values via the values property:

symbol accuracy_class {
  name "Accuracy class"
  type enum
  values [A, B, C, D]
  reference { R60-1-3-7-1 }
}

4.1. General

The latex property provides rendering hints for documentation generators. It does not affect runtime behavior.

4.2. Syntax

The latex value is a string containing valid LaTeX math-mode markup. The documentation generator wraps it in \(...\) or \[ ... \] as appropriate.

4.3. Conventions

• Use plain letters for variables: f, x, n
• Subscripts: n_{LC}, E_{max}
• Superscripts: x^2, 10^{-3}
• Greek letters: \alpha, \beta, \Delta
• Operators: \times, \cdot, \leq, \geq
• Text in math: \text{MPE}, \mathrm{C_H}

4.4. Default behavior

If latex is omitted, the documentation generator uses the symbol's identifier verbatim.

4.5. Example

symbol C_C {
  name "Creep"
  type number
  unit "v"
  latex "C_C"
  reference { R60-1-5-5-1 }
}
symbol C_DR {
  name "Dead load output return"
  type number
  unit "v"
  latex "C_{DR}"
  reference { R60-1-5-5-2 }
}

Renders as C_C and C_{DR} (with subscript) respectively.

5.1. General

Symbols link to normative sources via the reference property. This provides traceability from the formal symbol back to its printed definition.

5.2. Syntax

symbol <SymbolID> {
  // ...
  reference { <ReferenceID> { <ReferenceID> } }
}

Multiple references are allowed. The first listed is the canonical source; subsequent ones are additional sources.

5.3. Resolving references

A reference { R60-3-2-1-2-4 } requires a top-level reference R60-3-2-1-2-4 { ... } declaration elsewhere in the model. The parser:

1. Collects all reference declarations 2. Validates that every symbol's reference { ... } points to a declared reference 3. Emits an error if a symbol references an undeclared source

5.4. Example

reference R60-1-5-3-2 {
  document "OIML R 60-1:2021"
  clause "5.3.2"
  title "Maximum permissible errors on type evaluation"
}
symbol MPE {
  name "Maximum permissible error"
  type number
  unit "v"
  reference { R60-1-5-3-2 }
}

5.5. Why this matters

The chain symbol → reference → external document enables:

• Bidirectional search ("find all symbols defined in R 60-1 §5.3.2")
• Compliance checking ("is every used symbol traceable to a normative source?")
• Documentation generation (render a symbol index with citations)

6.1. Symbol declaration

SymbolDecl   = "symbol" ID "{" { SymbolProperty } "}" ;
SymbolProperty = "name" STRING
               | "definition" STRING
               | "type" SymbolType
               | "unit" STRING
               | "latex" STRING
               | "values" "[" ID { "," ID } "]"
               | "reference" "{" { ID } "}" ;
SymbolType   = "number" | "integer" | "string" | "boolean" | "enum" ;

6.2. Lexical conventions

As per the forms grammar (see formal-grammar-forms ).

6.3. Top-level placement

SymbolDecl may appear at the top level of a model, alongside other declarations.