[Paper Review] Declarative Event-Based Workflow as Distributed Dynamic Condition Response Graphs

Thomas Hildebrandt, Raghava Rao Mukkamala|IT University Of Copenhagen (IT University of Copenhagen)|Oct 19, 2011

Business Process Modeling and Analysis24 references17 citations

TL;DR

This paper introduces Dynamic Condition Response Graphs (DCR-Graphs), a declarative, event-based workflow model that generalizes prime event structures and enables flexible, constraint-driven process modeling. By using four primitive relations—condition, response, include, and exclude—it supports dynamic, distributed workflows with visual run-time state tracking and a formal mapping to Büchi automata for verification.

ABSTRACT

We present Dynamic Condition Response Graphs (DCR Graphs) as a declarative, event-based process model inspired by the workflow language employed by our industrial partner and conservatively generalizing prime event structures. A dynamic condition response graph is a directed graph with nodes representing the events that can happen and arrows representing four relations between events: condition, response, include, and exclude. Distributed DCR Graphs is then obtained by assigning roles to events and principals. We give a graphical notation inspired by related work by van der Aalst et al. We exemplify the use of distributed DCR Graphs on a simple workflow taken from a field study at a Danish hospital, pointing out their flexibility compared to imperative workflow models. Finally we provide a mapping from DCR Graphs to Buchi-automata.

Motivation & Objective

• Address the rigidity of imperative workflow models by proposing a declarative alternative that supports flexible execution and evolution.
• Overcome limitations of LTL-based approaches by providing a visual, user-friendly notation that avoids complex logic syntax.
• Enable dynamic and distributed process modeling through role-based event assignment and support for infinite behaviors.
• Provide a formal foundation for workflow execution and verification using a conservative generalization of prime event structures.
• Facilitate practical adoption by offering a prototype engine and integration with model checkers like SPIN.

Proposed method

• Define DCR-Graphs as a directed graph with events as nodes and four relations: condition (→•), response (•→), include (→+), and exclude (→−).
• Introduce markings to represent the run-time state of a DCR-Graph, enabling visualization of active and enabled events.
• Generalize prime event structures by replacing causal order with dual condition and response relations to model progress and dependencies.
• Extend the model to allow dynamic inclusion and exclusion of events, enabling finite representation of infinite behaviors.
• Assign roles and principals to events to model distribution and coordination across multiple actors.
• Provide a formal mapping from DCR-Graphs to Büchi automata to characterize acceptance conditions for finite and infinite runs.

Experimental results

Research questions

• RQ1 How can a declarative workflow model support flexible execution and evolution without requiring full re-specification?
• RQ2 Can a visual, constraint-based notation be both human-readable and formally grounded for verification?
• RQ3 How can dynamic behavior, including infinite runs and event reconfiguration, be modeled and represented finitely?
• RQ4 What is the formal relationship between DCR-Graphs and established models like prime event structures and Petri nets?
• RQ5 To what extent can DCR-Graphs express the same behaviors as LTL while remaining more accessible to end users?

Key findings

• DCR-Graphs provide a conservative generalization of prime event structures, preserving their formal properties while adding dynamic behavior and distribution.
• The model supports weak concurrency fairness through its dual condition and response relations, enabling correct handling of non-deterministic execution.
• The graphical notation allows direct visualization of run-time state via markings, improving usability and transparency for non-expert users.
• A formal mapping to Büchi automata enables model checking and formal verification of both finite and infinite executions.
• The prototype implementation integrates with the SPIN model checker, demonstrating feasibility for tool-supported workflow analysis.
• The approach outperforms LTL-based models in usability while maintaining sufficient expressiveness for real-world workflows, as validated in a hospital case study.