Events may afect the unfolding of other events in several ways. It happens, for instance, when we have an event that consists of a variation of what constitutes the objects that participate in an external, main event - e.g., by replacing parts of some of its participants or by adding/removing portions of the matter of which the participants are made. With that, such side events may result in qualitative changes in the participants of the main event. Sometimes the modified qualities may play a role in the dynamic of the main event. In such cases, any side event that afects these qualities will indeed have an efect on how the main event unfolds. Given this particularity, such a type of side event fill an important position in several domains and an understanding of its ontological nature is in order for a good conceptual modeling of those domains. Thus, in this paper, based on the idea of events as entities delimited by systems, we present an ontological account of auxiliary events, i.e., events that influence the unfolding of other events. We illustrate the proposed idea with a case study from the field of Geology.
In Computer Science, an ontology is the specification of a system of categories accounting for a
certain view of the world [
Even so, there are certain issues regarding events with which current approaches cannot properly deal. For example, they lack an account of how certain events can afect the unfolding of other events. This issue corresponds to the cases in which the sequence of stages in the Proceedings of the XVI Seminar on Ontology Research in Brazil (ONTOBRAS 2023) and VII Doctoral and Masters COoNnTsOorBtRiuAmS o2n02O3:n1to6ltohgSiems(iWnaTrDonOO2n0t2o3lo),gByrRaessieliaar,cBhrianzBilr,aAzuilgust 28 - September 01, 2023. nEvelop-O CEUR Workshop Proceedings course of an event is not exclusively determined by the interaction of its participants. Instead, in these cases, some of such stages partially result from the contribution of external elements.
Dealing with such a scenario is important in domains that rely on interference between processes. This is the case, for example, of process industries – such as the chemical or petrochemical industries – in which the unfolding of a main production process is modulated by several secondary processes (e.g., the heating/cooling of chemical reactors in order to control the rate of reaction that is taking place inside it, or the mixing of additives into a fluid in order to ease its flow through pipelines). A good model of how an event can afect another could help both in designing process plants as well as in decision-making during production. An account of how events influence one another is also useful for scenarios in which we are not able to directly observe the happening of a given event – such as geological and other nature processes – but can acquire good information about side events that involve some of the objects that participate in the main event and have an influence on it. Thus, a model of such side events can help in making inferences about the unfolding of the event of interest.
With that, in this paper, we propose an ontological account for what we call auxiliary events,
i.e., events that afect the unfolding of other events, which is based on a view of events as entities
delimited by systems [
In this section, we present the basic notions needed to convey the idea we propose in this work. We start by presenting some basic entities (e.g., objects and particularized properties). Then we proceed by describing contextual entities (e.g., situations and systems) that consist of arrangements of the basic ones. Finally, we employ the previous notions to convey the account of events we considered in this work.
Continuants are things that continue to exist through time while maintaining their identity,
being wholly present at any time point they are present [
Finally, dispositions are individualized properties that present characteristic manifestations
under some stimulus conditions, corresponding to what we usually refer to as potentialities,
propensities, capacities, tendencies, liabilities, and so on [
In this work, we regard a situation as an instantaneous, particular configuration of a part of
reality that is understood as a whole [
We also regard a (concrete) system as a complex object composed of a collection of at least
two interrelated material components forming an integrated, unitary whole [
In this work, we consider that two systems overlap if they share some common object. It may be the case of two systems that share a common component or whose components share a common part, or that a component of one system is part of a component of the other system, or even that one system is a component or part of a component of the other system. As a last remark, given this description of the notions of situation and system, we can assume the existence of a special type of situation that consists of a snapshot of a system at a given time, corresponding to the configuration of the components of such a system at that point.
Events are broadly characterized as things that happen in time. An event is usually regarded
as a transition among successive states of the world [
Given that, whenever a disposition is manifested, we necessarily have a system composed of at least two objects and a dispositional connection between them. Then, every event that is the manifestation of some disposition requires a system in order to happen. Its initial situation is a snapshot of a system with its components arranged in a way that activates certain of their dispositions. The situation the event brings about after that is another configuration of the same system that results from the manifestation of those dispositions. Therefore, for every disposition manifestation, there is a corresponding event consisting of a transition between snapshots of a system. Moreover, the resulting snapshot of the system may consist in an arrangement of its components in order to further activate their dispositions, which keeps the event going on. This recurrent correspondence between the manifestation of dispositions and the transition between snapshots of the system that activates them suggests the pervasive nature of this type of event. With that, we have the notion of system-invariant event, i.e., an event whose course is composed of situations that are snapshots of a single system.
In a system-invariant event, its participants maximally compose a system that persists during the happening of the event and whose connections are responsible for the manifestations of the dispositions that bring about the successive situations in the course of the event. Also, it is said that such a system delimits the event by delimiting the portion of reality that is subject to the event. Thus, being a participant of a system-invariant event at an instant t consists of being, at t, a component of the system that delimits the event and vice versa.
In this section, we introduce the notion of auxiliary events and the criterion to characterize an event as such. To guide the discussion, we start with an illustrative example to clarify the intuitions underlying the notion of auxiliary events. Then we elaborate on the nature of the efect that such events may have on other events and present the required conditions for attributing such type of efect to an event.
Let us consider the process of bacterial culture3, i.e., the process of multiplying bacteria by letting them reproduce in a culture medium4. With some simplification, we will regard it as an 3https://en.wikipedia.org/wiki/Microbiological_culture 4“A solid, liquid, or semi-solid designed to support the growth of a population of microorganisms” https://en.wikipedia. org/wiki/Growth_medium. event delimited by a system composed of a microbial colony and a culture medium, which are connected by a relation of containment such that the medium contains the colony. This relation of containment qualifies as a dispositional connection for exposing the nutritive capacity 5 of culture medium to the metabolic capacities of the bacterial colony.
Now, let us consider an ideal scenario A (fig. 1(A)) in which a bacterial culture process cult happens during 3 hours (from t1 to t4), involving a colony col, initially composed of 1000 individuals, and a culture medium med whose composition allows the colony to double its bacteria count every hour. Therefore, after 3 hours ( i.e., at time t4), the size of col reaches 8000 individuals.
Nevertheless, bacterial cultures are processes very sensitive to laboratory conditions, such as temperature or exposition to contaminants, and certain incidents may happen. Hence, let us consider that things actually happened as described in scenario B (fig. 1(B)). Here, instead of cult, another bacterial culture process cult’ takes place during the same time interval [t1, t4], also involving col and med as participants, starting in the same conditions (i.e., col composed of 1000 individuals and med allowing the colony to double its size every hour). However, diferently from cult, one hour after the start of cult’ (i.e., at t2), an event of antibiotic contamination cont happens, through which a small portion of antibiotic ant becomes part of the medium med. With some simplification, we will regard it as an event delimited by a system composed of ant 5Which we will regard as the ability of the medium to support the growth of bacteria (www.ncbi.nlm.nih.gov/pmc/ articles/PMC229120/) and med, which are connected by a relation of contact that exposes the solubility of ant to the dissolving ability of med.
Due to the presence of ant in its composition, from time t3 onward, med only supports a 50% hourly growth of the colony col. Hence, at time t4, col only reaches the size of 6000 individuals rather than the 8000 individuals that it would have achieved if cont had not happened.
As we can see, the actual bacterial culture cult’ and its modal counterpart cult have many similarities, i.e., they are events of the same type, having the same delimiting system, happening at the same time interval, and starting from the same initial conditions. Despite that, their courses are markedly diferent. The incorporation of a portion of antibiotic ant into the culture medium med changes the composition of med, which makes it exhibit a weaker nutritive capacity at t3. In consequence, at the last situation in the course of cult, the colony col is 1/4 smaller than it would be at the same time point in the course of cult’. This divergence in the nutritive capacity of med at t3 and in the size of col at t4 amounts to the efect of the side event of antibiotic contamination cont on the unfolding of the actual cult’ event. Specifically, such an efect consists of a deviation from the default course that an event of bacterial culture, with initial situation cult’, would have in the absence of any interference – such as the course of the counterpart event cult.
Given its contribution in delineating the course of cult’, cont would be what we will call an auxiliary event in relation to the main event cult’. Here, we regard an auxiliary event as an event that overlaps with, but is not part of, another main event and has some efect on the unfolding of such a main event. Thus, an auxiliary event has three main characteristics: (1) it is associated with a counterfactual efect on the main event, (2) it is a transformation of a portion of reality that overlaps with that of the main event, and (3) there is some causal link between the unfolding of the auxiliary event and the main events. We explore each of these characteristics in what follows.
Every auxiliary event has a counterfactual efect on its main event. This efect consists of the contrast between the course of the actual main event and the course of its counterpart event, delimited by the same system as the main event, starting from the same initial conditions (e.g., same system composition and structure) and at the same time, that would have taken place if the auxiliary event had not happened. In other words, it is the diference between the course of the main event and the sequence of snapshots that its delimiting system would present at the same time points if the auxiliary event had not happened.
Such a diference basically consists of the course of one of such events containing a situation that is not in the course of the other. That is to say, the courses of both events are equal up to a certain point but diverge after this point. It may be the case that the courses of both events have equivalent situations at a given time, which are succeeded by a distinct situation in the course of each event. For instance, the courses of cult’ and cult are equal up to time t2 but diverge with respect to the situations that obtain from time t3 onwards. That is, situations cult’1 and cult’2 are, respectively, identical to situations cult1 and cult2 (i.e., they obtain at the same time points, include the same colony col and medium med standing in the same contains relationship, with col having the same size and med having the same nutritive capacity), but situations cult’3 and cult’4 are distinct from cult3 and cult4 in terms of med nutritive capacity and col size.
For an auxiliary event to afect the unfolding of an ongoing main event, the efects of the auxiliary event on its subject portion of reality must be in some way ‘communicated’, so to speak, to the main event. Here we propose that this ‘communication’ is enabled by both events being transformations of a shared portion of reality. In this way, the efect of the auxiliary event over its subject portion of reality is also an efect over the portion of reality subject to the main event – and, therefore, can act as an input condition for the unfolding of the main event.
This is so because when one event evA is a transformation of a portion of reality that overlaps with the portion being transformed in another event evB, there is always something in evB (e.g., a participant, part of a participant) that can also be afected by the occurrence of evA. With that, evB may not fully determine the configuration of its respective portion of reality at some time point. In such a case, there will be a situation s in the course of evB that is not exclusively brought about by the interaction of its participants as they were arranged in the preceding situation. Instead, s will have some contribution of external objects, which are participants of evA. In other words, there will be a situation s in the course of evB that would not have been brought about if evA had not happened, which corresponds to a counterfactual efect of evA over evB (as exposed in section 3.2). Given this description, we have the sort of overlap between events – which we will call subject-overlap – needed to allow an auxiliary event to afect the unfolding of another, main event.
As discussed in section 2, in the case of a system-invariant event, it is a system that delimits the portion of reality that is subject to it. Therefore, two system-invariant events overlap if (1) they temporally overlap and (2) their delimiting systems overlap during a time interval in which both events are happening. To capture this idea we define the subject-overlap relation as follows: Definition 1. subject-overlap(ev1,ev2) =def A binary relation between an event ev1 delimited by the system sys1 and another event ev2 delimited by the system sys2 such that (1) ev1 and ev2 temporally overlap at a time instant t; and (2) overlap(sys1,sys2) at t.
To illustrate, in the example described in section 3.1, we have a subject-overlap relationship between the bacterial culture cult’ and the antibiotic contamination cont. Those events temporally overlap during the interval [t2,t3] and, during this interval, their underlying systems overlap by having the culture medium med as a common component, and the antibiotic portion ant composes the delimiting system of cont, but not that of cult’.
It is worth noting that even though a subject-overlap between two events allows an event to afect the unfolding of the other, it does not entail that one event will indeed afect the other. Sometimes, the efect of an event on the portion of reality it shares with another event has no impact on the unfolding of the latter (e.g., a change in the color of a car during a race would not afect the race). In other cases, such an efect does influence how the overlapping event will unfold (e.g., the cooling of a reactor generally slows down a chemical reaction that is going on inside it). That is, although necessary, subject-overlap is not a suficient condition for an event to afect another.
Another central characteristic of an auxiliary event is that it is not simply associated with a counterfactual efect on its main event; rather, it must produce such efect. To put it another way, there must be a causal link between the happening of the auxiliary event and its associated efect on the main event. This feature distinguishes a genuine auxiliary event from an event that also subject-overlaps the main event and that is indeed correlated with a counterfactual efect on it, but that is not the origin of such an efect.
As discussed in section 3.2, if an event aux has a counterfactual efect on another event main, there will be at least one situation s in the course of main that would not be established if aux had not happened. If aux is indeed causally related to such efect on main, aux must in some way contribute to bringing about s. Hence, the causal link between aux and its efect on main lies in the mechanism that supports this contribution, i.e., the role of aux in the disposition manifestations that jointly result in s.
In the course of an undisturbed event u, every situation is brought about by the manifestation of dispositions of participants of u, whose stimulus conditions are all provided by the way in which such participants were arranged in the preceding situation. Stating diferently, u comprehends all the elements required for the disposition manifestations that bring about each situation in its course. In contrast, in the course of an event main afected by an auxiliary event aux, at least one situation s will result from the manifestation of dispositions whose required activation elements are not all provided in the preceding situation. That is, the bringing about of s will comprise the manifestation of a disposition whose activation requires something external to main, which is provided by aux.
As exposed in section 2.1, the activation of a disposition d requires at least 5 elements: (1) the disposition d, (2) the bearer of d, (3) a property p that is complementary to d, (4) the bearer of p, and (5) a relationship between the bearers of d and p. With that, for aux to contribute to bringing about s, s must (at least partially) result from the manifestation of a disposition such that one of the elements for its activation is provided by aux rather than main. Thus, the causal link between aux and its efect on main lies in the fact that one of the elements for the activation of the referred disposition is, at the time when the disposition is triggered, in the system that delimits aux and not in the system that delimits main.
To illustrate, in the example from section 3.1, the efect of cont on cult’ consists of the presence of ant in the composition of med from t3 onwards, which means a weakening of the nutritive capacity of med. Thus, the causal link between cont and such efect on cult’ lies in the fact that the incorporation of ant into med results from the manifestation of the dissolving ability of med, which requires its exposition to the solubility of ant, which composes the delimiting system of cont but not that of cult’.
Turbidity currents (also known as turbidity flows ) are among the most important processes of
transport of sediment 6 from the continental shelf to the deep sea [
Physically speaking, a turbidity current is the movement of a mixture of turbulent fluid and
suspended sediment (which are habitually called interstitial fluid and suspended sediment
load) down an inclined seabed slope toward the deep marine floor. In a turbidity current, the
sediment load is kept in suspension by the interstitial fluid turbulence7 [
Turbidity currents are markedly influenced by some associated processes, especially those
of erosion and deposition. Erosion is the process by which seabed sediment is incorporated
into a flowing fluid-sediment mixture [
In this section, we briefly characterize turbidity currents as system-invariant events and erosion as an auxiliary event in relation to a turbidity current.
Given what was exposed, we can regard a turbidity current as a process of transport of suspended
sediment by a turbulent fluid . It is a process that takes place due to a complex interaction between
the solid and fluid phases of the mixture, which are treated as first-order participants with
specific roles in the process. Namely, the sediment in suspension is regarded as the suspended
‘load’8 to be transported [
With that, we propose modeling a turbidity current as an event delimited by a flowing
fluidsediment mixture, which we regard as a system with two components, i.e., an interstitial fluid
and a suspended sediment load, connected by turbulently suspends relationship that exposes
the suspended-sediment transport capacity of the flowing fluid [
This view is backed up by the literature from the domain, with plenty of descriptions of
the fluid-sediment mixtures as entities composed of two components involved in complex
interactions [
The fluid-mixture system exists in an environment that includes a seabed, which is connected
to the fluid-sediment system by a shear contact relation. Domain literature reflects this view
in various passages that characterize the seabed as an external element that modulates the
evolution of the flowing system [
Hence, we can regard erosion as the event by which an amount of sediment ceases to be part of
the sediment that constitutes the seabed and enters in suspension in the flowing mixture, becoming
part of its sediment load. Also, erosion can be seen as the manifestation of two reciprocal
dispositions, namely, the erosivity of the flowing mixture, i.e., its ability to cause erosion9
[
With that, we have all the elements to characterize erosion as a system-invariant event delimited by a system composed of a flowing fluid-sediment mixture, its suspended sediment load, a seabed, and the amount of sediment that is eroded. The bulk of its structure includes a shear contact relation between the flowing mixture and the seabed, which exposes the erosivity of the former to the erodibility of the latter. It also includes the part-of relation between the load and the flowing mixture and between the eroded sediment and either the seabed or the lfowing mixture, depending on the stage of the erosion.
Given this description, erosion genuinely qualifies as an auxiliary event in relation to a main turbidity current. First of all, it has a counterfactual efect on the turbidity current since, upon the occurrence of erosion, an amount of sediment is added to the suspended load of the turbulent lfuid-sediment mixture. This consists of a variation in the volume of the carried load that could not be achieved only by the interaction of the participants of the turbidity current. Such an efect is enabled by the subject-overlap between erosion and its main turbidity current, which consists of their underlying systems sharing a common component, i.e., the suspended load, and the whole turbulent fluid-sediment mixture system is also a component of the erosion system. Finally, there is a causal link between erosion and the variation in the volume of the suspended load. In particular, the variation happens through the manifestation of erosivity of the flowing mixture, which is manifested only when exposed to the complementary disposition of erodibility that inheres in the seabed, which participates in erosion but not in the current. 9www.collinsdictionary.com/dictionary/english/erosivity
This view is also confirmed by domain literature. In the context of turbidity currents, erosion
is regarded as an associated process through which seafloor topography influences flow behavior
[
Figure 2 brings a schematic representation of an erosion event as an auxiliary event of a turbidity current. The erosion is a transition through situations comprising a seabed bed, a lfowing fluid-sediment mixture mix, its suspended sediment load load, and the eroded sediment eroded sedim, which loses the part-of relation with bed and acquires a part-of relation with load. The turbidity current involves the interstitial fluid fluid and the suspended sediment load load and consists of the change in their location loc over time (here, from region r1 to region r4). The efect of the erosion on the turbidity current consists of the change in the volume vol of load from its original value x to the increased value x+e such that e is the volume of the eroded sediment eroded sedim.
This work presented an ontological analysis of how an event can afect the unfolding of another. It was based on the view that an event is a transition among situations that are snapshots of a single system of connected components so that the participants in the event at an instant t are the components of such a system at t. With that, we proposed the notion of auxiliary event as an event aux that operates over a portion of reality that overlaps with the one that is subject to another event main, and that, by transforming such a shared portion of reality, can afect influence the course of main.
A noteworthy point of our work is that it sheds light on a contextual facet of events. The notion of auxiliary event allows us to describe an influence network among events that is not possible to account for when relying only on the usual subsumption, mereological, temporal, or successively causal relations. With that, our approach may help in modeling types of events that interfere with another event in various ways, e.g., causing the entry/exit of participants during its occurrence (e.g., manufacturing processes, with diferent tools being employed in diferent stages and new components being added to the unfinished product) or qualitatively altering the participants of an event in a way that impacts its dynamic (e.g., heating the oil inside a pipeline in other to increase the flow rate of an oil transport process).
Such an account of how the happening of an event can be molded by its surrounds seems
to have a close relation with the ideas of context and of event modifiers discussed in [
Finally, following our reflections in [
Research supported by CAPES (Funding Code 001), CNPq, and Project Petwin (financed by FINEP and LIBRA Consortium).