Public Processes Legal Issues Verification using YAWL

Kaouther Mezaache and Latifa Mahdaoui

Department of Computing, University of Science and Technology Houari Boumediene, Algiers, Algeria

Keywords: Public Process Verification, Legal Requirements Verification, Design-Time Verification, Soundness Property,

YAWL.

Abstract: Improving public processes to build an effective e-government system has become a necessity for many

governments. For the purpose of providing quality electronic services to citizens, businesses and other public

institutions. However, this is not as easy as it seems, due to the nature of e-government system and the

requirements of its processes specially the legal ones. As a matter of fact, the law is one of the important

sources of knowledge that rigorously describes administrative procedures and their end results. Hence,

process verification will be a mandatory task to detect and to prevent process problems at the deployment

phase. Therefore, this paper aims to introduce an approach to assess public process legal issues against

soundness property using YAWL.

1 INTRODUCTION

Governments become nowadays subject of

modernization through the adoption of information

and communication technologies (ITC) (Cherouana

et al, 2017). Therefore, building an efficient e-

government system is one of the ultimate objectives

of contemporary governments. For the sake of

enhancing the access to and delivery of government

information and services to citizens, business

partners, and government entities (Layne and Lee,

2001).

It is worth mentioning that e-government cannot

be achieved by simply implementing good software

(Alpar and Olbrich, 2005), even though these later

have proven their effectiveness in the private sector.

This is due to the e-government system nature and

requirements of its processes, namely, political,

organizational, technical and especially the legal

requirements (Cherouana et al, 2017). Indeed,

according to (Hasan et al, 2015) the policies and

regulators become one of the most significant barriers

to reengineering public administration processes.

Nevertheless, (re) engineering the public

processes without respecting legal constraints is

rather dangerous (Alpar and Olbrich, 2005) and leads

to inconsistent situations which may cause an

enormous loss of trust and reputation (Hasan et al,

2015).

However, regarding their informal nature,

regulations could be source of many problems

(Aravanis et al, 2018): 1. Misinterpretation of legal

texts because of the difficulty of understanding. 2.

Lack of legislation or Legal vacuum. 3. Self-

contradictions 4. The origin of legal texts from

several sources can lead to overlapping regulations

at different levels of authority, and could sometimes

produce contradictions or conflicts between them. 5.

Frequent change and evolution of regulation over

time …Etc.

For these and other reasons, large amount of work

exists in the field of business process verification, to

maintain e-government’s proper functioning. Among

them, the approach proposed in the current paper. It

allows to perform a twofold process model

verification: formal and informal verification. Using

YAWL (see section 3), that will act as a simulator,

allowing to apprehend processes design issues that

may affect performance before proceeding to their

implementation.

The reminder of this paper is organized as

follows: some related works are presented in the

following section with a discussion about it. Section

3 introduces the proposed approach of process

verification as well as the research context. Section 4

will describe the case study used to illustrate the

approach application. Finally, we conclude the paper

with proposition of some future perspectives in

section 5.

Mezaache, K. and Mahdaoui, L.

Public Processes Legal Issues Veriﬁcation using YAWL.

DOI: 10.5220/0010454702890296

In Proceedings of the 16th International Conference on Evaluation of Novel Approaches to Software Engineering (ENASE 2021), pages 289-296

ISBN: 978-989-758-508-1

289

2 RELATED WORK

According to (Groefsema and Bucur et al, 2013), the

formal business process verification has mainly four

goals: 1) Basic process correctness: aim to verify

process basic properties such as termination, 2)

Process compliance: aims to address and provide

solutions to the alignment between business process

and regulations (Hashmi et al, 2018), 3) Variability:

aims to support different versions of the same

process. It uses rules to specify how each version of a

process should behave, 4) Processes including

multiple parties: aim to verify the compatibility

between processes (for example).

The following table (Table 4) summarizes some

of the related work about business process

verification.

Table 1: Related work.

Article Verification Method

Verification

Purpose

(He et al,

2018)

The authors propose

a workflow nets with

incorporation of data

constraints and define

four level of

soundness and use the

reachability graph to

verify the soundness

property of the

processes.

Detecting

errors from

the data-flow

perspective

(missing data,

conflicts….).

(Aravanis et

al, 2018)

The idea here is to

reduce the workflow

while preserving its

properties using six

novel reduction rules,

then substituted the

analysis of the

soundness property of

the reduced workflow;

thus, carry out the

verification of

soundness property on

a smaller WF-Nets.

Verifying the

crucial

business

processes of a

system with

large size and

big

complexity.

(Birukou et

al, 2010)

This method

combined two

constraints solving

methods: CLP

(Constraints Logic

Programming) and

SMT (Satisfiability

Modulo Theory), they

report that SMT

approach has much

better results than the

CLP, except for a

Verifying the

modal

specifications

of the

business

processes

(that describe

the necessary

behaviours of

processes).

conflict free workflow

net. For this reason,

they combined the two

of them.

(De Moura

et al, 2010)

Business rules are

represented using the

OCL language,

considered as a pre- or

post-condition for

business processes

represented by the

UML Activity

Diagram. The model

validation is based on

the simulation of the

execution of process

instances based on

specific scenarios. If

the violation is

detected -with the help

of the USE tool- than

the execution is

stopped and the

violation is reported

and returned to the

modeler whom could

rectify the rule or the

input or outputs.

Checking the

compliance

of business

processes

with the

business rules

(represented

in OCL) at

the Run-Time

phase.

(Corradini et

al, 2010)

The authors defined a

quality framework

which classifies the

delivery processes of

an e-government

digital processes and

they implemented a

tool applying a model

checking techniques,

to verify that

developed e-

government digital

processes satisfy the

properties defined in

the quality framework

Ensuring

quality of

governmental

processes by

comparing it

to a set of

properties.

(Gilliot and

Accorsi et al,

2009)

They use the model-

checking technique

based on linear

temporal logic (LTL)

and statistical

reasoning. And the

result could be one of

the 4-valued logic:

“true,” “false,”

“presumably true,” or

“presumably false.”

Anticipating

obligation

violations at

“Run-time”.

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Table 1: Related work (Cont.).

Article Verification Method

Verification

Purpose

(Jiang et al,

2015)

Authors propose A

compliance and

consistency checker

framework CCCF that

takes as input:

business process

represented with

modelling language

then formalized into

event-sequence and

regulations

represented with

Norms Nets. Then

provides three results:

whether regulations

are consistent,

whether business

process are compliant

and in case of non-

compliance which

operation to be

rectified.

Analysing

both

processes

compliance

with

regulations

and self-

consistency

of laws

(Governatori

et al, 2006)

Business

constraint in the

contract is represented

by a rule in FCL

language. While the

business processes

scenarios are

represented by BPMN

then transformed into

an event pattern (same

thing for the contract

conditions in order to

facilitate the checking

task). The comparison

results between the

events are as follows:

ideal “none violation

detected”, sub-ideal

“violation detected but

could be repaired”, a

non-ideal “a violation

detected without a

reparation” and

irrelevant situation

“there isn’t a rule to

apply in this situation.

Use of logic

in analysing

the

compliance

of business

processes

with business

contracts.

2.1 Discussion

From the works of the table above, we observe that

there are several characteristics to process

verification, that could be divided like so:

2.1.1 Concerning the Process

1. Process Perspective: the focus is on one of the

process perspectives (Van Der Aalst and Ter

Hofstede, 2005) namely: control-flow, data-flow or

resource-flow perspective.

2. Process Sector: the process could be for the

public sector or for the private sector (Corradini et al,

2010).

3. Process Complexity: i.e., a complexity factor

which specifies how far the process is complicated

(Aravanis et al, 2018).

2.1.2 Concerning the Method of Verification

1. Verification Phase: means at what phase of the

process life-cycle the verification will be performed.

According to (Hashmi et al, 2018) there are three

main strategies, namely: de-sign-time, run-time or

audit (post-execution).

2. Verification Type: stands for: 1) compliance

verification of the process with norms or 2)

consistency verification of the regulations governing

processes, or 3) both.

3. Employed Methods: refers to the methods used

to perform the verification, naming: use of logic, use

of well-known AI methods or conceptual ones…. etc.

2.1.3 Discussion

The majority of the studied papers focus on the

control flow perspective except for the (He et al,

2018) that treats the data flow perspective, without

precising the targeted sector excluding (Corradini et

al, 2010) that aims at proposing a quality framework

to ensure public processes (governmental processes)

quality. They also perform their verification at

different time of the process-life-cycle. Also, we

notice that the works mostly emphasis on the

compliance verification of processes with the

regulations -norms- and few of them have evoked the

regulation consistency verification. In the exception

of (Jiang et al, 2015) that perform the two of them at

once. We remark that various methods were used to

help in proposing verification approaches, we can

cite: logic in multiple works (Gilliot and Accorsi et

al, 2009) (Governatori et al, 2006). Finally, many

papers have used the model checking techniques to

check the applicability of the verification method.

The ultimate objective of proposing this approach

for process verification; is to detect legal problems

(legal vacuum, legal conflicts and obsolete law),

through analyzing public processes during the design-

time phase (build-time).

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3 PUBLIC PROCESS

VERIFICATION APPROACH

3.1 Definitions

The following definitions are necessary for

understanding the rest of the paper:

Workflow-net: is a subclass of Petri nets often used

in the context of workflow management and business

process management (systems) (Process Mining

course) WF-nets specifies the dynamic behaviour of

a single case in isolation (Van Der Aalst, 2000). In

fact, one of the most important notions in the WF-nets

is that it has a well-defined input start and output end.

Yawl: stands for Yet Another Workflow Language, is

a workflow system (business process management

system) fully open-sourced. It is a language with a

strictly defined execution semantics inspired by first:

Petri Nets with graphical representation, able to

support verification (Corradini et al, 2018), also

YAWL is based on the workflow patterns

(http://www.workflowpatterns.com). Yawl is a

successor of Workflow-Nets (Adams and Hofstede,

2020).

Soundness Property: A Workflow-net is sound if and

only if the following properties hold:

 Proper Completion: if the sink place is

marked, all other places are empty,

 Option to Complete: it is always possible to

reach the marking that marks just the sink

place, and

 Absence of Dead Parts: for any transition

there is a firing sequence enabling it.

Law: the law is any system of regulations to govern

the conduct of the people of a community, society or

nation, in response to the need for regularity,

consistency and justice based upon collective human

experience (Law dictionary).

Obsolete Law: The term is applied to statutes which

have become inoperative by lapse of time, either

because the reason for their enactment has passed

away, or their subject matter no longer exists, or they

are not applicable to changed circumstances, or are

tacitly disregarded by all men, yet without being

expressly abrogated or repealed (The law dictionary).

Legal Void (Vacuum): intuitively refers to a space in

which there is no law, is considered as a gap in the

law. In fact, it has a largely pejorative connotation for

those who feel that the law is the best means of

binding individuals and to ensure that everyone's

freedom is respected, while it will have a very

positive connotation for people who see the law as a

negative constraint and therefore, in its absence, a

space of freedom (Dinh, 2007).

Figure 1: Framework for governmental processes design

(Cherouana et al, 2017).

3.2 Research Context

In previous works, a framework dedicated to generate

public processes from their legal texts was proposed

(Mahdaoui and Cherouana, 2012). The developed

solution was an evolutionary framework comprising

a sequence of two major phases allowing a priori

design in compliance with the law (see Fig. 1),

namely: a) legal design, b) operational design

(Cherouana et al, 2017).

The following table gives a brief description of

each phase as well as their inputs and outputs:

Table 2: Public process design phases.

N° Phase Input Description Output

Legal

Design

Legal

corpus

Extract from

the legal texts

the different

characteristics

constituting

the public

process and

represent it

with the

workflow-net

formalism.

Global

Model

(Abstract

Process)

Operational

Design

Current

models

Abstract

process

Add the

operational

aspect not

necessarily

defined in the

law to the

abstract

process and

specific to

each public

institution.

Public

Process

ready to

deployme

Despite, the conformity of the generated process

model with the law, it cannot be definitely said that it

is valid and ready to be deployed yet. For the simple

reason that regulations and legal texts may include

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some shortcomings that certainly have a negative

impact on process validity.

Accordingly, we believe that detecting gaps and

inconsistencies in the legislation is of great

importance to ensure that the designed public process

will act properly when implemented.

Hence, we aim to propose verification approaches

at different steps of the process development as

depicted in the diagram (see Fig. 2), to be specific: a)

legal corpus verification, b) abstract process

verification, and c) global model verification.

Figure 2: Steps of process development with verification

tasks.

Indeed, we have previously proposed a pre-

verification approach (Mezaache and Mahdaoui,

2020) a verification of the consistency of the legal

corpus, that will serve as a basis for extracting the

process at a very early stage (before "legal design"

phase).

Therefore, in the current paper, we are interested

in the verification of the Abstract Process (see the

coloured verification task in figure 2).

3.3 Abstract Process Verification

Approach

So that, in this sub-section, we detail the verification

of the generated model from the “Legal Design”

phase: the abstract process. Which is a twofold

procedure: Formal verification & Informal validation.

3.3.1 Formal Verification

The abstract process is the result of the legal design

phase in the development of the process. During this

phase a law study is performed to extract the

activities, roles and constraints of the to-be process,

besides the logic of the control-flow of the latter, then

represented it in workflow-net formalism. At this

stage, our concern in this paper is to check that the

generated process is not subject to problems.

According to PR Will Van Der Aalst soundness

property is at the same time basic and most important

property that each WF-net model should satisfy for

being correct and free of anomalies.

YAWL, is concerned with the design time

detection of certain undesirable characteristics in

process models. It provides two verification

approaches; the first approach is based on the

ResetNet theory which supports the use of reduction

rules while the second proposes the use of the

wofYawl analysis algorithm (based on the concept of

transition invariants “petri-net”) (Adams and

Hofstede, 2020).

Basically, the abstract process (i.e., global model)

will be verified by the Reset-Net analysis tool to

check the soundness property. Remember that the

process model is an abstraction of the law, as such

whether the result of the analysis is positive or

negative, it reflects the consistency of the law.

Here comes our proposal to interpret the results of the

soundness property legally.

Results Interpretations: To do so, we proceed by

interpreting the negative results of soundness

property analysis:

Deadlock: In fact, the existence of deadlocks means

that one of the two properties “Option to complete”

or “Proper completion” is not verified. Indicating,

that there is no appropriate path to take (set of actions)

through the model. Which implies that no

corresponding legal text(s) that explains what is the

next step or how to deal with this situation: this is

called the law void.

Dead Parts (Transitions): The existence of dead

parts means that the property “Absence of dead parts”

is not verified. This means that there are tasks that

cannot be performed in any scenario, this could

indicate that the law is obsolete and doesn't respond

to the needs anymore, or simply it is not useful.

The following table represents the resulting links

between the four soundness properties and legal

problems:

Table 3: Correspondence table between WF-nets properties

(soundness) and legal problems.

Problem Encountered in The

Process Model Analysis (Wf-

Nets Properties)

Legal Interpretation

(Legal Problems)

P1: Existence of deadlocks

(The execution is blocked

before reaching the end).

=> property 'Option to

complete /proper completion'

is not checked.

- Legal void.

- Law incompleteness

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Table 3: Correspondence table between WF-nets properties

(soundness) and legal problems (Cont).

Problem Encountered in The

Process Model Analysis (Wf-

Nets Properties)

Legal Interpretation

(Legal Problems)

P2: Existence of transitions

that cannot be executed in any

scenario (Adams and

Hofstede, 2020).

=> property 'Absence of dead

parts' is not checked.

- Legal texts not

useful.

- Law obsolete.

- Law that does not

fulfil the needs.

P3: Multiple tokens in a place

at the same time.

=> Safeness property is not

checked.

-Conflict situation.

-Inconsistency.

It can be concluded that if there exists problems in

the analysis report of the soundness property, then the

legal texts on which the process is based are source of

these problems. Therefore, it is necessary to return to

the correspondence table to extract the appropriate

legal interpretations of the problems encountered.

3.3.2 Informal Validation

The abstract process needs to be approved by public

institution managers, owing to the fact that this model

is considered as a draft that each public institution

will enrich/complete it with its own operational

aspect (new activities, roles, constraints, gates…etc.).

That’s why, public institution has an extremely

important role in the final decision of the process

model validity.

The results of the formal verification with both

interpretations and eventual recommendations will be

sent to the public institution for study. Even though

the formal verification may contain some issues, it is

up to them to decide whether these problems are fatal

and need to be resolved, so the development process

will be suspended until solutions are put in place or

not.

This validation is informal, it comes back to the

fact that the decision is made by humans and could

not be formalized or automated.

4 CASE STUDY

We have chosen the process of managing competitive

entrance exams to the Higher School of Social

Security 'HSSS' (public institution) to obtain a

professional master's degree, for applying the

proposed validation approach. Three categories of

applicants can be distinguished: 1) External

applicants: coming from universities, preparatory

schools, etc. 2) Applicants from the social security

organisms, and 3) Foreign applicants: from foreign

countries.

The process for the first category was generated

from these legal texts 1) executive decree n°649 from

the Ministry of Higher Education and Scientific

Research 'MHESR' official site:

https://www.mesrs.dz/fr/chapitre3 , and from 2) the

school internal texts, in BPMN language. However,

the second and third categories were generated from

only internal texts because of the lack of legislation.

 Process Generation in BPMN:

Case 1: First Category

Figure 3: A part of the process: ' Verification of the result

of the university course' in BPMN.

Case 2: Second Category

Figure 4: A part of the process in BPMN for competitors

from the social security organisms.

 Process Transformation:

Then, the process will be transformed to the

workflow-nets formalism.

Case 1: First Category

Figure 5: The transformed process model in YAWL.

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Case 2: Second Category

Figure 6: The transformed process model in YAWL.

 Process Analysis (Problems Identification):

The process will be verified using the Reset-net

analysis tool of YAWL. It gives the observation about

the three properties of the soundness property:

Case 1: first category

Figure 7: The analysis results of soundness property by

ResetNet.

Case 2: second category

Figure 8: The analysis results of soundness property by

ResetNet reveals deadlocks for the second category.

 Report Generation and Recommendations:

Case 2: second category

Table 4: Recommendations for the process of competitors

from the social security organisms.

Problem number Recommendations/Diagnosis

P1: is detected

- Need to Legislate Laws

concerning the competitors from

the social security organisms by

the MLSS

Discussion.

This case study was a sort of comparative application

of the presented approach on two process model

variants: the external competitors and those from the

social security organisms.

The results showed that the soundness property of

the modelled process of external competitors (first

category) are maintained, so it can surely be said that

the process is valid and could be safely deployed.

Nevertheless, the verification of the second

variant process (second category) pointed out some

problems: " deadlocks ", returning to the

correspondence table, this is due to the "legal

vacuum", i.e., the lack of legal texts clarifying how to

deal with competitors registration files. So, the

process isn’t valid and legislation activity is needed.

5 CONCLUSION

The effectiveness and efficiency of public processes

are the key for e-government system success and

improvement. Unfortunately, this cannot be achieved

without maintaining compliance with the law.

In this context, the generated processes comply

with the law because they are intended for the public

sector.

Nevertheless, the law can sometimes be source of

problems, resulting in the invalidity of the process,

which could fail once deployed.

We believe, therefore, that detection of law

deficiencies could help tremendously in improving

public processes.

Hence, we propose an approach that interpret the

results of correctness analysis of soundness property

of the process. By leveraging the analysis features

offered by workflow-net (YAWL tool).

These interpretations allow to detect legal texts

problems whom the process is based on. Then, a

report will be sent to the public administration

managers to proceed the informal validation and give

the final decision.

Since this type of analysis or verification is tidily

concerned with the model quality (Van Der Aalst in

Process Mining course). We intend to proceed the

data perspective verification to integrate more

semantics and to put interest in both content and

model in future works.

REFERENCES

Adams, M., & Ter Hofstede, A. (2020). YAWL User

Manual. User manual, The YAWL Foundation.

Alpar, P., & Olbrich, S. (2005). Legal requirements and

modelling of processes in e-government. Electronic

journal of e-government, 3(3), 107-116.

Aravanis, T., Demiris, K., & Peppas, P. (2018, November).

Legal Reasoning in Answer Set Programming. In 2018

IEEE 30th International Conference on Tools with

Artificial Intelligence (ICTAI) (pp. 302-306). IEEE.

DOI: 10.1109/ICTAI.2018.00055

Birukou, A., D’Andrea, V., Leymann, F., Serafinski,

J., Silveira, P., Strauch, S., & Tluczek, M. (2010,

Public Processes Legal Issues Veriﬁcation using YAWL

295

December). An integrated solution for runtime

compliance governance in SOA. In International

Conference on Service-Oriented Computing (pp. 122-

136). Springer, Berlin, Heidelberg.

Cherouana, A., Mahdaoui, L., & Khadraoui, A. (2017).

BPM-based framework for e-government processes

improvement: legal requirements integration.

International Journal of Intelligent Information and

Database Systems, 10(1-2), 21-50.

Corradini, F., Falcioni, D., Polini, A., Polzonetti, A., & Re,

B. (2010, August). Designing quality business

processes for e-government digital services. In

International Conference on Electronic Government

(pp. 424-435). Springer, Berlin, Heidelberg. DOI

https://doi.org/10.1007/978-3-642-14799-9_36.

Corradini, F., Fornari, F., Polini, A., Re, B., & Tiezzi, F.

(2018). A formal approach to modeling and verification

of business process collaborations. Science of

Computer Programming, 166, 35-70. DOI

https://doi.org/10.1016/j.scico.2018.05.008.

De Moura Araujo, B., Schmitz, E. A., Correa, A. L., &

Alencar, A. J. (2010, March). A method for validating

the compliance of business processes to business rules.

In Proceedings of the 2010 ACM Symposium on

Applied Computing (pp. 145-149). DOI https://doi.

org/10.1145/1774088.1774117

Dinh, A. M. H. (2007). Le « vide juridique » et le « besoin

de loi ». Pour un recours à l'hypothèse du non-droit.

L'Année sociologique, 57(2), 419-453.

Gilliot, M., & Accorsi, R. (2009). Runtime predictions of

policy violations in automated buisness processes.

Extended Abstract: presented at Prime Life/IFIP

Summer School Program, 7-11.

Governatori, G., Milosevic, Z., & Sadiq, S. (2006, October).

Compliance checking between business processes and

business contracts. In 2006 10th IEEE International

Enterprise Distributed Object Computing Conference

(EDOC'06) (pp. 221-232). IEEE.

Groefsema, H., & Bucur, D. (2013). A survey of formal

business process verification. Proc. Int. Sym. Business

Modeling and Software Design, Noordwijkerhout, The

Netherlands.

Hasan, M. M., Loucopoulos, P., Anagnostopoulos, D., &

Nikolaidou, M. (2015, December). Regulatory

requirements compliance in e-Government service

development. In 2015 18th International Conference on

Computer and Information Technology (ICCIT) (pp.

254-259). IEEE.

Hashmi, M., Governatori, G., Lam, H. P., & Wynn, M. T.

(2018). Are we done with business process compliance:

state of the art and challenges ahead? Knowledge and

Information Systems, 57(1), 79-133.

He, Y., Liu, G., Xiang, D., Sun, J., Yan, C., & Jiang, C.

(2018). Verifying the correctness of workflow systems

based on workflow net with data constraints. IEEE

Access, 6, 11412-11423.

Jiang, J., Aldewereld, H., Dignum, V., Wang, S., & Baida,

Z. (2015). Regulatory compliance of business processes.

AI & society, 30(3), 393-402.

Law dictionary, https://dictionary.law.com/Default.aspx?

selected=1111, last accessed 20/02/2020

Layne, K., & Lee, J. (2001). Developing fully functional E-

government: A four stage model. Government

information quarterly, 18(2), 122-136.

Mahdaoui, L., & Cherouana, A. (2012). Towards a

methodological framework for the Government Process

Management. In International Conference on Research

Challenges in Information Science (RCIS).

Mezaache, K., & Mahdaoui, L. (2020, September). Law

analysis to support public process design. In

Proceedings of the 13th International Conference on

Theory and Practice of Electronic Governance (pp.

742-745).

Process Mining: Data Science in Action,

https://www.coursera.org/learn/process-mining/, last

accessed 20/02/2020.

The law Dictionary, https://dictionary.thelaw.com/

obsolete/, last accessed 20/02/2020

Van Der Aalst, W. M. (2000). Workflow verification:

Finding control-flow errors using petri-net-based

techniques. In Business Process Management (pp. 161-

183). Springer, Berlin, Heidelberg.

Van Der Aalst, W. M., & Ter Hofstede, A. H. (2005).

YAWL: yet another workflow language. Information

systems, 30(4), 245-275.

ENASE 2021 - 16th International Conference on Evaluation of Novel Approaches to Software Engineering

296