A formal ontology describing LCA methodology
The Life Cycle Assessment (LCA) methodology captured as an ontology formalised in the Web Ontology Language
Introduction
In a previous post we saw how a process specification perspective can be applied to provide some structure and semantics for methodology description and execution, taking the Life Cycle Assessment (LCA) methodology as example. In this article, we’ll apply this perspective and expose a well-rounded ontology that captures the full Life Cycle Assessment (LCA) methodology description. To keep the core structure of the ontology within context, we’ll reuse the four basic notions provided by the Process Specification Language (PSL) ontology (ISO18629–1:2004). These notions are sufficient for modelling the backbone of LCA methodology description and execution.
- Activity: Activities help define reusable behaviours that may or may not have occurrences. The concept of activities is very important when it comes to general methodology description.
- Activity Occurrence: Activity occurrences are unique executions of activities that span over time. The concept of activity occurrences helps capture execution level semantics of activities and, therefore, provides a basis for modelling LCA methodology execution semantics.
- Timepoint: Timepoints are distinct points in time. Timepoints are required for modelling the start and end times of activity occurrences and how they span over time. Timepoints constitute another concept relevant to LCA methodology execution.
- Object: Objects are abstract or concrete entities (i.e., neither activities, nor activity occurrences, nor timepoints) that are required for describing the things that are the participants in or influence activities and their occurrences. The concept of objects is very important in both LCA methodology description and execution capture.
Scope of work
The scope of this work is specifically on LCA methodology description, which means that the focus is on activities and objects. To keep the LCA ontology in the general context of process specification, we’ll still acknowledge the concepts of activity occurrence and timepoint, for anyone wishing to extend the ontology to capture LCA methodology execution semantics. In the ontology development process, I was also inspired by other PSL notions for capturing, e.g., activity-subactivity relations, participation of objects, and a few others. Additionally, I’ve had to come up with my own set of relations for catching activity-object and activity-activity associations.
Note: In my previous post I identify the need for extending PSL if we are to use it as a process specification perspective for methodology description.
Activity and process concepts
The diagram shown below depicts the hierarchy of activity and process concepts to support LCA methodology description semantics. The types of activities identify the main phases in LCA methodology description like inventory analysis and life cycle interpretation. The model also captures programme management activity types since these work hand in hand with the process design and process management of LCA as a programme.
Object Concepts
In the diagram shown next, various kinds of objects are identified. These object types capture the concrete and abstract things that can participate in and influence LCA activities in various ways, e.g., different deliverables are required during the LCA process for reporting on specific topics of interest.
Occurrence and Temporal Concepts
Two classes are acknowledged in the model to allow for capturing occurrence and temporal concepts. These classes are ActivityOccurrence and Timepoint, which although being outside the scope of LCA methodology description, are still relevant to a process specification perspective.
Deliverables
There are two useful outputs from this work:
- Firstly, there’s an OWL ontology which defines the full set of concepts and relationships. This provides a formal basis for exchanging the semantics of the knowledge model. Click here for more details on the LCA methodology ontology.
- Secondly, there’s an interactive graphical representation of the LCA ontology where you can navigate around the various concepts and drill down into their textual definition. Note that, for clarity, I only show the activity-activity and activity-object relationships. For a complete representation, please refer to the OWL version.
References
- ISO14040:2006. Environmental management — Life cycle assessment — Principles and framework.
- ISO18629–1:2004. Industrial automation systems and integration — Process specification language — Part 1: Overview and basic principles.