Re: #ontology Can we come up with a better term than "Flow Object"? #ontology

Elias Sebastian Azzi


Reading up that long email thread I wrote a summary of the different views expressed. I also summarise an article that describes another ontology for IE, rather different vocabulary, hoping it will help us see the ontology from a different perspective.



Alpha / Summary


Issue - Human vocabulary for BONSAI's core ontology

While there seems to be an agreement among the participants around the three core classes of the ontology (i.e. on their conceptual meaning), there is not yet a consensus on how these classes should be named in human readable language. There is however an agreement on the fact that the vocabulary used during the hackathon 2019 is not ideal. Most of the controversy lies in the term "flow object". This issue seems of high importance because it affects how people perceive the ontology, understand it and decide whether to take it up or not.


Below, we summarise the different views/suggestions on that issue, pros, cons and remarks.


V1. [Chris] "Flow object" is not consistent with the other terms of the ontology and is hard to related to. The alternative "item" is suggested.

Pro: definition of item is "an individual article or unit, especially one that is part of a list, collection, or set" which fits in the concept.

Pro: it echoes to fields of computer science and mathematics

Remark: activities are also part of a list/collection/set, according to that definition activities are also items of a collection of activities.


V2. [Chris] "Flow" is good but has no natural counterpart. An alternative for "flow" could be "exchange".


V3. [Agneta] Return to the published LCA ontology (Kuczenski et al. 2016), with the three terms Activity (a thing that happens), Flow (a thing in the world that exists because of some instance of an Activity), and Exchange (an established relationship between an activity instance and a flow instance).

Pro: (to verify) coherence with the vocabulary used by most industrial ecologist / (disagreement) in (1) the authors argue that terminology is not consistent between industrial ecologist, even for basic definitions.

(1) Pauliuk, S.; Majeau-Bettez, G.; Müller, D. B.; Hertwich, E. G. Toward a Practical Ontology for Socioeconomic Metabolism. J. Ind. Ecol. 2016, 20 (6), 1260–1272; DOI 10.1111/jiec.12386.


V4. [Rutger] In  ecospold1, only exchanges are defined. In ILCD data formats, both exchange and flows (i.e. flow objects) are defined. Environmental compartments are specified. In SimaPro platform, Flows do not include compartments, as in the Bonsai hackathon version. Exchange is not yet used, but is considered. At PRé, flow-objects are of two types: substances and products, but not perfect.

Con: flow and exchange are both dynamic terms


V5. [Matteo] Flow and Flow-object in the post-hackathon ontology are clear and well defined: they relate the Flow and the Object of the Flow (aka the Flow Object). In other words, by keeping the word "flow" in both definitions their link and subtle difference is kept explicit and forces the new-comer to think twice about these definitions.

Pro: all terms can be confusing, the advantage of Flow and Flow-object is that the difficulty is not hidden behind different terms, does not allow for misunderstanding to happen.


V6. [Bo] The vocabulary we use needs to distinguish between "the observation of a specific flow (22 kg input of steel) and the abstract flow-object (steel)".


V7. [Agneta] "hackathon vocabulary" -> "new vocabulary"

Flow-object => Flow

Flow => Exchange


Long List of Terms:

Flow object, entity, object, flux, item, thing, element, substance, component, Noumenon, Flow-item, commodity

Flow, Exchange, Phenomenon






Bravo / Looking at it from a different angle


This being said, I would like to add to the discussion the following points:

-          Matteo has a point: by using the work “flow” twice (in flow and flow-object) we keep the complexity explicit.


-          We seem to agree on the structure, but finding the right words for human communication is tricky: do we have to choose? In the end, examples speak by themselves. We will choose a term now, but we can keep the list of alternatives: the list helps clarify things!


-          Do we actually agree on the structure? Your discussions forced me to re-open that article by Pauliuk and co: they have the same goal as Bonsai, performed a review of all IE fields, and (wait for it) came up with a totally different wording. I would say that it is one level of abstraction higher than the current Bonsai ontology, and rather stimulating to read. Here some highlights:

o   Many inconsistencies of vocabulary and definitions exist within IE and even within certain fields e.g. LCA

o   Industrial ecologist describe socioeconomic metabolism by a bipartite directed graph (i.e. SUTs) or directed graph

o   Five key definitions:

Definition 1, Sets: A set is a collection of distinct objects

Definition 2, Hierarchical, mutually exclusive and collectively exhaustive (H-MECE) object classification: An HMECE object classification is a grouping of a given set of objects into an H-MECE collection of sets.

Definition 3, Stock: A stock is a set of objects of interest.

Definition 4, Process: A process is a set-based description of one or several events of interest, expressed in terms of the objects of interest that are involved in these events during their course.

Definition 5, Flow: A flow is a description of a particular type of event, where objects are preserved and move from one set a to another set b.

o   In sounds very different, but when you read the article in details, all the issues we face are somehow discussed. Including how to handle the properties of objects of interest (see Figure 2)

o   Definition 2 is of interest for the correspondence table group






From: <> On Behalf Of Chris Mutel
Sent: den 5 april 2019 12:46
Subject: Re: [bonsai] #ontology Can we come up with a better term than "Flow Object"?


I added a table with what I could make of the existing systems, and the possible alternatives we have discussed, here: Feel free to edit this if you think I have made a mistake.

> To re-iterate: Flow is a verb

Flow can be a verb or a noun, and there is something to be said for having all the core terms be nouns (I think everything else is).

Join to automatically receive all group messages.