Chimera: Composable Semantic Transformation Pipelines

Chimera is a framework implemented on top of Apache Camel offering components to define schema and data transformation pipelines based on Semantic Web solutions.

:toolbox: The chimera-deployment-templates repository offers ready-to-use templates to deploy a Chimera conversion pipeline in different environments.

:arrow_forward: The chimera-tutorial repository provides a complete example of a Chimera conversion pipeline.

Goals

The motivating scenario is about many stakeholders with an interoperability need. To avoid the definition of point-to-point conversions, an any-to-one centralized mapping approach based on Semantic Web technologies (and a reference ontology used as global conceptual model) offers the following advantages:

• Let stakeholders keep using their current legacy systems
• To obtain interoperability with other actors in the ecosystem, a stakeholder only needs to define lifting mappings from the adopted standard to the reference ontology, and lowering mappings from the reference ontology to the standard
• Knowledge graph as an additional valuable product of the conversion

The main goal of Chimera is to facilitate the definition of conversion pipelines in the described scenario. In particular, the main objectives are:

• to enable the definition of so-called semantic conversion pipelines (using Semantic Web-based solutions for data transformation) to obtain message-to-message mediators or batch converters;
• to minimise the amount of code to be written, in principle, the aim is to completely avoid coding by just configuring the various components provided.

Architecture

The main assumption of Chimera is that it is possible to break down a converter (or mediator, using the naming conventions specific to Enterprise Service Buses) into smaller, composable and reusable entities. The inspiration to this approach is taken from the Enterprise Integration Patterns, breaking a data-based process into blocks to be composed, that are implemented in Apache Camel. Chimera provides additional blocks for the Apache Camel framework enabling the reuse of production-ready Camel components already defined (e.g., integration with input/sink data sources) and/or the implementation of additional blocks (e.g., custom pre-processing).

The RDF graph can be interpreted as a variable which is shared among all the blocks in a conversion process. A basic conversion process based on Semantic Web technologies generates triples from the incoming message/dataset (lifting) and uses the resulting graph to extract data which is used to populate the structure of the destination message/dataset (lowering). Furthermore, the conversion can require enrichment with some background knowledge (being either a set of ontologies or a set of master/lookup data).

With this high-level process in mind, we defined a core set of blocks:

• Lifting or Graph Construction: this block takes a structured message as input, and enriches the RDF graph with the triples obtained by applying a "mapping" to the input.
• Graph Transformations: this block loads a set of RDF files, or generates a set of triples (e.g. CONSTRUCT queries or ontology enabled inferences) and loads them into the RDF graph.
• Graph Validation: this block loads a set of ontology files into the RDF graph, inference rules can generate additional triples enriching the graph.
• Lowering or Graph Exploitation: this block applies a “mapping” to data extracted from the RDF graph, and produces a structured message as output.

Use Chimera

The project has a parent POM that can be used to trigger Maven goals and compile the project locally. The different modules can be imported as dependencies from Maven Central. Chimera is currently composed of three Apache Camel Components, available as sub-projects in this repository. All the components rely on the rdf4j library to handle the RDF graph.

• camel-chimera-graph Camel component used to create and manipulate RDF knowledge graphs.
• camel-chimera-rmlmapper Camel component used to lifting using the rmlmapper-cefriel library
• camel-chimera-mapping-template Camel component able to implement both lifting and lowering steps using the mapping-template library

N.B. The camel-chimera-mapping-template includes camel-chimera-graph as a dependency. Therefore, when using the camel-chimera-mapping-template component, you do not need to include the camel-chimera-graph dependency separately.

Chimera Pipeline Configuration

Apache Camel provides support for multiple domain-specific languages (DSL) to define routes, with the primary options being the Java, XML, and YAML DSLs. When utilizing the YAML DSL, routes can be configured graphically through Camel Karavan, as detailed in the approach outlined here.

Projects

• Mouseworld Lab for Network Digital Twin (NDT): https://github.com/Mouseworld-Lab/mouseworld-kg
• SMARTY: Scalable and Quantum Resilient Heterogeneous Edge Computing enabling Trustworthy AI https://www.smarty-project.eu/
• SmartEdge: Semantic Low-code Programming Tools for Edge Intelligence https://www.smart-edge.eu/
• TANGENT: Enhanced Data Processing Techniques for Dynamic Management of Multimodal Traffic https://tangent-h2020.eu/
• SPRINT: Semantics for PerfoRmant and scalable INteroperability of multimodal Transport http://sprint-transport.eu/
• SNAP: Seamless exchange of multi-modal transport data for transition to National Access Points https://snap-project.eu/

Publications

• Scrocca M., Grassi M., et al. (2024) Intelligent Urban Traffic Management via Semantic Interoperability Across Multiple Heterogeneous Mobility Data Sources. In: The Semantic Web – ISWC 2024. Springer. https://doi.org/10.1007/978-3-030-62466-8_26
• Scrocca M., Carenini A., et al. (2024) Not Everybody Speaks RDF: Knowledge Conversion between Different Data Representations. In: 5th International Workshop on Knowledge Graph Construction co-located with the ESWC 2024. CEUR-WS. https://ceur-ws.org/Vol-3718/paper3.pdf
• Grassi M., Scrocca M., Comerio M., Carenini A., Celino I. (2023) Composable Semantic Data Transformation Pipelines with Chimera. In: 4th International Workshop on Knowledge Graph Construction co-located with the ESWC 2023. CEUR-WS. https://ceur-ws.org/Vol-3471/paper9.pdf
• Scrocca M., Comerio M., Carenini A., Celino I. (2020) Turning Transport Data to Comply with EU Standards While Enabling a Multimodal Transport Knowledge Graph. In: The Semantic Web – ISWC 2020. Springer. https://doi.org/10.1007/978-3-030-62466-8_26

Commercial Support

If you need commercial support for Chimera contact us at chimera-dev@cefriel.com.

Contributing

Before contributing, please read carefully, complete and sign our Contributor Licence Agreement.

When contributing to this repository, please first discuss the change you wish to make via issue or any other available method with the repository's owners.

License

Copyright (c) 2019-2025 Cefriel.

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.