SOL: Structural Operational Language — Engineering Grounding Protocol for AI-Assisted Mechanical Analysis

Structural Operational Language (SOL) is an experimental semantic grounding protocol designed for engineering reasoning across heterogeneous systems, including human engineers, AI agents, CAD environments, and diagnostic workflows. The protocol introduces a lightweight topology-oriented intermediate representation intended to reduce semantic drift during long-horizon technical discussions and multi-agent coordination. SOL defines structured engineering primitives, causal operators, observability semantics, and layered interaction models (SOL-H, SOL-A, SOL-IR, SOL-CAD/DW) for stabilizing engineering intent across communication boundaries. This publication presents the current experimental specification (v1.2), including token architecture, protocol layers, usage examples, limitations, and proposed validation methodology.