=Paper=
{{Paper
|id=Vol-1289/kese10-06_submission_9
|storemode=property
|title=Towards an Ontological Analysis of BPMN
|pdfUrl=https://ceur-ws.org/Vol-1289/kese10-06_submission_9.pdf
|volume=Vol-1289
|dblpUrl=https://dblp.org/rec/conf/ecai/SanfilippoBM14
}}
==Towards an Ontological Analysis of BPMN==
https://ceur-ws.org/Vol-1289/kese10-06_submission_9.pdf
Towards an ontological analysis of BPMN
Emilio M.Sanfilippo1,2 , Stefano Borgo2 , and Claudio Masolo2
1
Institute of Industrial Technologies and Automation, ITIA-CNR, Italy
emilio.sanfilippo@itia.cnr.it
2
Laboratory for Applied Ontology, ISTC-CNR, Italy
Abstract. bpmn is a de-facto standard with more than 70 commercial
tools that currently support its use. However, its the semantic ambigu-
ities jeopardize its implementation. We perform an ontological analysis
of important constructs of bpmn like activities and events to highlight
their implicit commitments.
Keywords: Ontological analysis, bpmn, State, Event, Activity
1 Introduction
Business process (BP) modelling concerns the analysis and representation of the
activities by which companies coordinate their organisation and work, produce
goods, interact with each others and customers. The goal is a common con-
ceptual modelling language that can be easily understood to facilitate business
communication. The Business Process Model and Notation (bpmn) [9] is one of
such BP languages and is a OMG standard with more than 70 commercial tools
that currently supports its use3 . bpmn focuses on graphical constructs and lacks
formal semantics. Thus, it presents conceptual ambiguities regarding the inter-
pretation of its metamodel and the supporting software tools are not guarantee
to interoperate. We use ontological analysis to dwell into the backbone elements
of bpmn like activity and event. The goal is to investigate whether the standard
is (possibly implicitly) committed to some (coherent) ontological perspective.
The remainder of the paper is organized as follows: Section 2 describes the state
of the art about the analysis of bpmn. Section 3 looks at a bpmn process diagram
to highlight some problematic issues. Sections 4 gives the ontological analysis of
our target notions.
2 State of the art
The literature about bpmn focuses on three types of analysis: (i) the syntac-
tic analysis, (ii) the behavioral analysis, and (iii) the ontological analysis. The
syntactic analysis aims at defining the structural constraints that bpmn-models
3
This work is part of a larger study [11] that will be presented at the International
Conference on Formal Ontology in Information Systems (FOIS 2014). In this version
we assume some familiarity with bpmn.
must satisfy. [4] presents the bpmno meta-ontology implemented in OWL [7].
bpmno allows reasoning with semantically annotated processes and it enriches
bpmn with, e.g., temporal information. Similarly, [1] provides a bpmn ontology
encoded in the WSML language [2]. The behavioral analysis looks at what can
happen during the execution of a well-formed bpmn model like, e.g., the existence
of deadlocks or livelocks [3]. This (static) analysis of a process model considers
the semantics underlying the schema only for procedural information and is not
relevant for our work in this paper. Finally, the ontological analysis focuses on
the characterization of the primitives of the language. [8] discusses the OPAL
reference framework and characterizes the specific kinds of activities or events
present in a given model, but it lacks a characterization of the general difference
between bpmn-activities and bpmn-events. [5] uses the ontology ABDESO to
distinguishes actions from other events. The authors find quite a few ambiguous
and redundant elements, as well as missing concepts in bpmn. Finally, [10] looks
at the mutual relationship between bpmn and the Bunge-Wand-Weber (BWW)
foundational ontology. The paper highlights some ontological shortcoming in the
first release of the standard with respect to ontological completeness, construct
overload, construct excess and construct redundancy.
In this paper we are interested in the ontological analysis of bpmn with the
aim of clarifying how one can understand the notions of activity and event. We
carry out our study in two ways: first by ontologically analyzing the information
provided by the bpmn standard, and then by characterizing our findings on these
concepts with the Dolce ontology [6]. We are not proposing an evaluation of
bpmn with respect to an ontology; we rather use the ontology to find (possibly
implicit) commitments of the standard, identify business related elements that
the standard does not address, and to highlight the variety of interpretations
that are consistent with these constraints.
3 Activities and Events in bpmn
The bpmn diagram in Fig. 1 represents a process with four participants: Pur-
chaser, Service provider A, Service provider B and Service provider C. The pro-
cess starts when the event type None in the Purchaser pool happens. This is
followed by the execution of task Request Quotes which ends with the sending
of a message to each service provider participant in the process. Once a service
provider receives the message, it starts its own process consisting in sending a
quote to the Purchaser. After this, the service provider process ends. When the
Purchaser receives at least two quotes, it executes the Assess the Quotes task
after which the process ends for the Purchaser provided the condition Sufficient
reserve amount? is satisfied. Otherwise, the process is back to the Request Quotes
and flows again.
The reason why some parts of the process are marked as activities and others
as events is not immediately clear. In the diagram below, messages are exchanged
between the process participants by using tasks of type Message send. However,
in bpmn one could also use a Message as throw event (not showed in Figure
Fig. 1. bpmn process diagram, taken from [9, p.362]
1), which models the sending of a message as well. The meanings of these two
different constructs – that seem to model the same thing – is not immediately
clear. The bpmn specification [9] provides little help in clarifying the distinction
between activity and event. The bpmn Quick Guide4 states that “[...] an Event
maps to a time point on a time line [while] a Task [activity] maps to a time
interval”. This seems to mean that events are instantaneous while activities last
in time, which implies that temporal atomicity is a discriminating property.
Nevertheless, bpmn does not commit to a theory of temporal points or intervals,
thus every reference to time remains vague. Another possibility is to understand
activities and (at least some) events in terms of endogenous vs exogenous entities:
the first are happenings controlled within the poll the latter are out of the control
of the pool.
4 Ontological analysis of bpmn events and activities
Events and activities in bpmn are connected to other events and activities in the
same (in a different) pool by solid (dashed) arrows; these arrows mark execution
precedence and thus temporal dependences. This reveals the temporal nature of
events and activities in bpmn. From the ontological viewpoint, we can classify
them as (some type of) perdurants or occurrents, in the sense of entities that
extend in time possibly by accumulating temporal parts. In the following we
use the Dolce taxonomy of perdurants—mainly the concepts of Achievement,
Accomplishment, State, and Event—to discuss and ontologically characterize the
difference between Activities and Events, and between Catch- and Throw-events.
4
http://www.bpmn.org
While we find helpful to use a foundational ontology like Dolce, we remark that
the analysis could be based on other ontological systems provided they include
a taxonomy of perdurants.
Activities and tasks: We have seen that bpmn activities are not instantaneous,
thus they take time to execute. In addition, bpmn distinguishes between two
types of activities: tasks, i.e., atomic activities and sub-processes, i.e., non-atomic
activities. The relationship between being instantaneous and being atomic is not
trivial given that a task can have a positive temporal extension.
In some ontological theory [12] it is assumed that perdurants extend in time
by having different temporal slices at different times. This would rule out bpmn
tasks because, by extending in time, they necessarily have (temporal) proper
parts, where ‘necessity’ is here used in the ontological sense, namely tasks have
temporal parts in all possible worlds. According to this perspective, a task like
Request Quotes is necessarily anti-atomic and anti-homeomeric, i.e., all its in-
stances have parts that do not belong to Request Quotes. The anti-homeomericity
is evident for bpmn sub-processes, whose structure is explicitly included in the
BPMN-model.However, it might be suggested that bpmn models the world at
some granularity, in the sense that tasks are considered to be atomic in the con-
text of the model even though they have temporal parts in the actual world. In
this case, tasks could be conceived as atomic or non-atomic depending on the
context, granularity, or perspective on the world. We talk in this case of concep-
tual modality, because the ontological status of tasks relies not on how they are,
but rather on how they are conceived within a certain conceptual framework.
We observe also that the mereological sum of two instances of a task like Send
quote is not an entity of the same type. This is consistent with the assumption
that bpmn activities represent units of work with the purpose of achieving given
business goals; they thus culminate with the achievement of the goal.
We can then conclude that by considering a strict ontological modality ac-
tivities are anti-atomic and anti-cumulative, i.e., they can be mapped to Dolce
accomplishments. Vice versa, by assuming a conceptual modality, only sub-
processes may be mapped to accomplishments. More generally tasks would be
mapped to Dolce events, i.e., as anti-cumulative types of perdurants with no
commitment on atomicity and homeomericity.
Catch events: We saw that events are instantaneous, consequently they are
temporally atomic, that is, they cannot extend over or throughout a temporal
stretch. Catch events like the reception of a message, are in general exogenous,
i.e., their happening is outside of the control of the pool they belong to or,
at least, of the branch of the pool process at stake. In this perspective None
start events could be understood as ‘the system is turned-on’. In addition, being
culminating perdurants the catch events are anti-cumulative. Anti-cumulativity
and atomicity characterize the subcategory of achievements in Dolce.
The process of Service Provider A in Figure 1 cannot proceed unless a trigger
is received, i.e., a message is received. Accordingly, if the system of this service
provider is ‘turned-off’, the message will never be received. Thus, behind a catch
event there is the assumption that the process is waiting to be triggered, i.e.,
the system is on a receiving mode.
Differently from activities, these kinds of perdurants (e.g., waiting) are home-
omeric—i.e., the temporal slices of waiting-instances (if any) are themselves
waiting instances—and cumulative—i.e., the mereological sum of two (immedi-
ately consecutive) waiting-instances is still a waiting-instance. Homeomeric and
cumulative perdurants are called states in Dolce. For example, Figure 1 indi-
cates that Service providers A, B and C are (by default) in a waiting status for
receiving messages. Thus, a catch event identifies (perhaps implicitly) a state
and it further indicates that the pool is committed towards a specific trigger to
occur.
However, on the same line of [10], one could consider catch events as state-
transitions. For example, the reception of messages can be understood by refer-
ring to two states: the state of ‘waiting for the message’ and the state of ‘message
received’, where the latter is the pre-condition for executing the successive task.
The trigger thus enacts a state transition and, in turn, the starting of the new
state enables the process to perform its subsequent tasks5 .In the case of None
catch (start, intermediate) the trigger that is holding the process is not spec-
ified. From our viewpoint, there are at least two possible views regarding the
semantics of this modelling construct. It might be a placeholder for the initial
temporal boundary of the process that in our example corresponds, as a logical
constraint, to ‘there are no parts of the process that precede the Request Quote
task’. In this case, the None catch bears no further ontological commitment. On
the other side, one can return to the idea of a (hidden) waiting state. The latter
case seems to be incompatible with the interpretation of the start event as ‘the
system is turned-on’.
Throw events: Similarly to catch events, throw events are instantaneous, then
temporally atomic, and anti-cumulative, i.e., in Dolce they are classified as
achievements. Differently from catch events, throw events tend to be endogenous:
actions under the control of the pool they belong to. Note that differently from
tasks, which can be conceived as structured perdurants, although atomic under
a certain granularity, throw events are punctual, thus intrinsically unstructured.
Throw None end events can be understood as the achievement of the whole
process, and, in a fashion similar to start events, they can be interpreted either
as an ontologically neutral placeholder in the model, as a logical constraint, or
as an (ontologically committed) achievement. Note that the throw end events
marked with a specific trigger icon, like Message, Terminate, Signal and Error,
indicate an achievement as well but now the culmination point is qualified: the
triggers that are specified in these cases (message, signal, termination and error)
are amongst the participating entities of the achievement.
5
The analysis of the causal dependencies among triggers, events and tasks could be
very informative.
5 Conclusions
We focused on the ontological analysis of the bpmn notions of activity (task) and
event, and classified them within the Dolce account of perdurant entities. The
results are still preliminary and the hope is that it can help to reach a deeper
understanding of the system; and to develop sound bpmn-driven ontologies. In
the future, we shall expand this first analysis and develop a formalization cap-
turing our results on bpmn.
Acknowledgements: This research is in part supported by the Gecko and
Pro2Evo projects of the “Fabbrica del Futuro” (funding: MIUR).
References
1. W. Abramowicz, A. Filipowska, M. Kaczmarek, T. Kaczmarek Semantically en-
hanced Business Process Modelling Notation. In M. Hepp et al. (Eds.), Semantic
Business Process and Product Lifecycle Management. Proceedings of the Workshop
SBPM 2007, Innsbruck, April 7, 2007
2. J. de Bruijn, D. Fensel, U. Keller, M. Kifer, H. Lausen, R. Krummenacher, A.
Polleres, L. Predoiu Web Service Modeling Language (WSML). W3C Member
Submission 3 June 2005 Available at: http://www.w3.org/Submission/WSML. Last
access March 2014
3. R.M. Dijkman, M. Dumas, and C.Ouyang. Semantics and analysis of business
process models in BPMN. Information and Software Technology, 50(12):1281–1294,
2008.
4. C. Ghidini, M. Rospocher, L. Serafini A Formalisation of BPMN in Description
Logics. Technical Report TR 2008-06-004, FBK-irst, 2008.
5. G. Guizzardi, G. Wagner Can BPMN Be Used for Making Simulation Models?
7th International Workshop on Enterprise & Organizational Modeling and Simula-
tion (EOMAS 2011), together with the 23rd International Conference on Advanced
Information System Engineering (CAiSE’11), London, UK.
6. C. Masolo, S. Borgo, A. Gangemi, N. Guarino, A. Oltramari.
WonderWeb Deliverable D18. Ontology Library. Available at:
http://wonderweb.man.ac.uk/deliverables.shtml, 2002. Accessed March 2014
7. D.L. McGuinnes, F. van Harmelen OWL Web Ontology Language. Overview. W3C
Recommendation 10 February 2004. Available at: http://www.w3.org/TR/owl-
features. Last access March 2014
8. M. Missikoff, M. Proietti, and F. Smith. Linking ontologies to business process
schemas. Technical Report 10-20, Istituto di Analisi dei Sistemi ed Informatica del
CNR, 2010. ISSN: 1128 - 3378.
9. Object Management Group (OMG) Business Process Model and Notation (BPMN).
Version 2.0, 2011 Available at: http://www.bpmn.org Last access March 2014
10. J. Recker, M. Indulska, M. Rosemann, P. Green. Do Process Modelling Techniques
Get Better? A Comparative Ontological Analysis of BPMN. Australasian Conf. on
Information Systems. Sydney, 2005
11. E.M.Sanflippo, S. Borgo and C. Masolo. Events and Activities: Is there an Ontology
behind BPMN? In: Formal Ontology in Information Systems, IOS Press, 2014
12. T. Sider, Four-Dimensionalism. An Ontology of Persistence and Time. Oxford:
Clarendon Press, 2001.