ISO 13584-20:1998

Overview

ISO 13584-20:1998 - "Industrial automation systems and integration - Parts library - Part 20: Logical resource: Logical model of expressions" defines a logical model and EXPRESS schemas for representing expressions used in parts libraries and industrial automation data exchange. It provides an EXPRESS schema for generic expressions and a specialized schema for expressions over integer, real, Boolean and string data types (based on ISO 10303-11). The standard focuses on the syntax, semantics, validation and exchange of expressions - including constants, variables and defined functions - and on functions that test properties such as integer evaluation and SQL mappability.

Key Topics

• EXPRESS schemas: formal ENTITY and function definitions for generic expressions and for numeric/Boolean/string subsets.
• Expression syntax and semantics: representation of literals, variables, unary/binary/multiple-arity expressions, and semantic constraints to ensure correctness.
• Variable modelling: syntactic representation, domain of values and semantic description (variable_semantics, environment, interpretation).
• Functionality for analysis:
  • Is_int_expr - checks whether a numeric expression should evaluate to an integer.
  • Is_SQL_mappable - tests whether an expression can be mapped to an SQL query.
  • Used_variables / Used_functions - identifies dependencies for evaluation and exchange.
• Exchange and validation: rules for exchanging expressions (constants and variables), ensuring acyclicity and semantic correctness.
• Scope boundaries: explicitly excludes assignment of values to variables in a context and runtime triggering mechanisms that evaluate expressions.

Applications

ISO 13584-20 is practical for organizations that need to exchange, validate and map symbolic expressions across engineering and enterprise systems:

• PLM/PDM and CAD/CAM vendors using parts libraries to represent parametric rules, formulas and constraints.
• Industrial automation and systems integrators who exchange configuration rules or parameterized component data.
• Data exchange and interoperability specialists implementing EXPRESS-based data schemas (ISO 10303) and mapping models to relational databases (SQL).
• Software developers building validation, model-checking or transformation tools that need to determine expression properties (e.g., integer-only, SQL mappability).

Related Standards

• ISO 10303-11 (EXPRESS language) - defines the expression language subset referenced by ISO 13584-20.
• Other parts of ISO 13584 (Parts library) - for broader component data modelling and exchange.

ISO 13584-20 is essential when you need a formal, exchangeable logical model of expressions for parts libraries and for mapping EXPRESS-based expressions to SQL and other implementation targets. Keywords: ISO 13584-20, EXPRESS schema, expressions schema, parts library, industrial automation, SQL mappability, ISO 10303-11.