Assurance via workflow+ modelling and conformance

TL;DR

This paper introduces a novel assurance approach called WorkflowPlus (WF+), which models safety processes through layered workflows emphasizing data relationships, and compares it with GSN, highlighting WF+'s advantages.

Contribution

The paper proposes WorkflowPlus, a layered workflow model for assurance that explicitly incorporates data relationships, and provides a detailed comparison with GSN.

Findings

WF+ models include process, data, and argument layers.

Explicit dataflow modeling distinguishes WF+ from GSN.

GSN does not fully meet assurance modeling promises.

Abstract

We propose considering assurance as a model management enterprise: saying that a system is safe amounts to specifying three workflows modelling how the safety engineering process is defined and executed, and checking their conformance. These workflows are based on precise data modelling as in functional block diagrams, but their distinctive feature is the presence of relationships between the output data of a process and its input data; hence, the name ``WorkflowPlus'', WF+ . A typical WP^+ model comprises three layers: (i) process and control flow, (ii) dataflow (with input-output relationships), and (iii) argument flow or constraint derivation. Precise dataflow modelling signifies a crucial distinction of (WP+)-based and GSN-based assurance, in which the data layer is mainly implicit. We provide a detailed comparative analysis of the two formalisms and conclude that GSN does not fulfil its promises.