Publications

Conference Papers


From Art to Engineering: An Architecture Evaluation Framework for Deep Graph Transformation Tasks

Paper submitted for peer review. Publication expected in late 2026.

Deep graph transformation lacks evaluation protocols for comparing architectures across structurally different graph transformation tasks. We introduce an evaluation framework for edge-level graph transformation that places nine architectures under a shared evaluation contract so that observed differences reflect architectural suitability rather than incidental experimental variation. Using thirteen graph-computation and real-world tasks drawn from a deep graph transformation taxonomy, we show that no single architecture dominates across tasks: suitability is governed less by model complexity or graph-theoretic complexity class than by the structural computation required. Dense models dominate when canonical or domain-specific features encode the relevant edge signal; graph-native models dominate when multi-hop relational verification is required; and global attention is useful only for some forms of long-range structure. Cross-task clustering recovers architecture-response groups that cut across the original taxonomy, suggesting an empirical task dimension based on four computational primitives. The framework provides reproducible baselines and experimental instruments for studying when relational inductive bias helps, fails, or becomes unnecessary.

Recommended citation: A. Machowczyk, S. De Sabbata and R. Heckel, "From Art to Engineering: An Architecture Evaluation Framework for Deep Graph Transformation Tasks", 2026.

Benchmark First: Defining Tasks for Graph Transformation Learning

Published in The 19th International Conference on Graph Transformation. INRIA Center, Rennes, France, 2026

Learning graph transformations from examples requires datasets for training and benchmarking. To establish which machine learning architectures are suitable for which kinds of problems, we need to experiment on a range of graph-computation tasks. In this paper, we propose a framework for defining such tasks and categorising them along four dimensions: complexity, input-output relation, graph type, and the structural changes they require. We apply the framework to 16 tasks for which we have implemented data generators or provided data sets in a unified interface. Our aim is to work towards a benchmark that supports the training and evaluation of graph transformation models in a framework that can be used by the wider community to support their own research, define more tasks, thereby extending and refining the framework.

Recommended citation: Machowczyk, A., Heckel, R. (2026). Benchmark First: Defining Tasks for Graph Transformation Learning. In: Archibald, B., Semeráth, O. (eds) Graph Transformation. ICGT 2026. Lecture Notes in Computer Science, vol 16624. Springer, Cham. https://doi.org/10.1007/978-3-032-29730-3_13
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Towards Graph-to-Graph Transformation Networks

Published in The International Workshop on Graph Computation Models. University of Twente, Enschede, Netherlands, 2024

Graph Neural Networks (GNNs) operate primarily by performing matrix operations, such as multiplication, Hadamard product, transposition and inversion, on graph adjacency matrices. Due to their essential use in machine learning, they are efficiently implemented even for large matrices. Instead, the complexity of finding a match of the LHS in the host graph, as required in rule-based graph rewriting, is worst-case exponential. GNNs perform a simple form of parallel graph rewriting where a single rule with a central node is applied to all nodes of the graph to aggregate data from all its neighbors. However, this model can only compute on node or edge attributes, not change the graph itself, and pattern matching is usually restricted to this node and its outgoing edges. We are interested in a GNN architecture that can efficiently implement general transformations from input to output graphs.

Recommended citation: A. Machowczyk and R. Heckel, "Towards Graph-to-Graph Transformation Networks" in GCM 2024. Post-Proceedings.
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From Message Passing to Actor Graph Neural Networks

Published in The International Workshop on Graph Computation Models. University of Twente, Enschede, Netherlands, 2024

Graph Neural Networks (GNNs) are neural networks operating on graphs to compute node- or graph-level properties, and predict nodes or edges. One of the basic forms are Message Passing Neural Networks (MPNNs) where each node sends a message to its neighbours based on its current state, then aggregates messages received from its neighbours to update their own state. Aggregation is expressed by the multiplication of feature vectors (carrying node attributes) with the adjacency matrix of the graph. At the most expressive level, we have a model reminiscent of actor grammars where actors can send and receive messages asynchronously, change their attributes, create or delete edges to other actors, create other actors and remove themselves from the graph. We would like to explore the following questions:
1. How can models at different levels be implemented efficiently using matrix operations?
2. For which types of problems are agent- or rule-based models competitive?
3. How can we assess the expressiveness of such models?

Recommended citation: R. Heckel and A. Machowczyk, "From Message Passing to Actor Graph Neural Networks" in GCM 2024. Post-Proceedings.
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Graph Rewriting for Graph Neural Networks

Published in The 16th International Conference on Graph Transformation. College Court, Leicester, UK, 2023

Nominated for the Best Paper award.

Given graphs as input, Graph Neural Networks (GNNs) support the inference of nodes, edges, attributes, or graph properties. Graph Rewriting investigates the rule-based manipulation of graphs to model complex graph transformations. We propose that, therefore, (i) graph rewriting subsumes GNNs and could serve as formal model to study and compare them, and (ii) the representation of GNNs as graph rewrite systems can help to design and analyse GNNs, their architectures and algorithms. Hence we propose Graph Rewriting Neural Networks (GReNN) as both novel semantic foundation and engineering discipline for GNNs. We develop a case study reminiscent of a Message Passing Neural Network realised as a Groove graph rewriting model and explore its incremental operation in response to dynamic updates.

Recommended citation: Machowczyk, A., Heckel, R. (2023). Graph Rewriting for Graph Neural Networks. In: Fernández, M., Poskitt, C.M. (eds) Graph Transformation. ICGT 2023. Lecture Notes in Computer Science, vol 13961. Springer, Cham. https://doi.org/10.1007/978-3-031-36709-0_16
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