=Paper=
{{Paper
|id=Vol-2383/paper8
|storemode=property
|title=Building an Executable Axiomatisation of the REA2 Ontology
|pdfUrl=https://ceur-ws.org/Vol-2383/paper8.pdf
|volume=Vol-2383
|authors=Wim Laurier,Satoshi Horiuchi
|dblpUrl=https://dblp.org/rec/conf/vmbo/LaurierH19
}}
==Building an Executable Axiomatisation of the REA2 Ontology==
https://ceur-ws.org/Vol-2383/paper8.pdf
Building an executable axiomatisation of the
REA2 ontology
Wim Laurier1[0000−0002−9448−248X] and Satoshi Horiuchi2
1
SMASH, Faculté ESPO, Université Saint-Louis - Bruxelles, Boulevard du jardin
botanique 43, 1000 Bruxelles
wim.laurier@usaintlouis.be
https://www.researchgate.net/profile/Wim_Laurier
2
Faculty of Commerce, CHUO University, 21225, 742-1 Higashinakano Hachioji-shi,
Tokyo 192-0393 Japan
satoshi@tamacc.chuo-u.ac.jp
https://ir.c.chuo-u.ac.jp/researcher/profile/00010558.html?lang=en
Abstract. This project aims at producing an executable version of the
Resource-Event-Agent ontology. This executable version is built with the
MERODE methodology, which guarantees coherence between class and
state diagrams. Where the MERODE CASE tool supports generating
Java code from conceptual diagrams, our aim is to produce fully REA-
compliant blockchain code with this methodology.
This project’s main innovation is the use of existence dependency and
event propagation to model increment and decrement as fundamental
stand-alone concepts that simultaneously affect economic resources, event,
agents and the nature of the stock-flows, participations and dualities be-
tween them.
The second – and most probably the most important – contribution of
this paper is the formalisation of the REA axioms as executable finite
state machines.
In the future, both of these innovations are believed to contribute to
the reliability of a generic semantic blockchain technology for both the
finance and logistics domain in both the traditional and the sharing
economy. As such it is expected to promote both traceability and ac-
countability in value networks and supply chains.
Keywords: REA ontology · MERODE · Blockchain · Model Driven
Architecture
1 Introduction
1.1 Blockchain
Blockchain is – by some – believed to be the silver bullet to solve almost any issue
in the world. The blockchain technology is particularly known for it’s applications
in finance (e.g. Bitcoin), although it’s impact on the non-financial economy (e.g.
2 Laurier & Horiuchi
logistics) is also growing rapidly (e.g. Provenance3 ). Where blockchain has an
impact in both finance and logistics, the full power of the technology has to
the best of our knowledge not been realised in both domains simultaneously.
What is needed is an approach that can link financial and logistical processes
to each other, to promote transparency, fair trade, and fight money laundering,
counterfeit and the funding of terrorism.
1.2 Introduction to REA & REA2
The Resource-Event-Agent (REA) ontology [5] has the power to unite financial
and non-financial value streams and has been shown to serve as a conceptual
foundation for blockchain implementations. [2] REA has a conceptualisation for
describing an organisation’s metabolism (i.e. the value chain[6]) from the inside
with it’s dependent or trading-partner view and supply chains with its inde-
pendent view [3], which is the perspective of a third party not taking part in
an economic exchange. The REA2 [4] ontology unites these two views demon-
strating by means of a operationalised mapping that the three perspectives on an
exchange (i.e. buyer, seller and third party) are – although semantically different
– information equivalent.
1.3 Content of this paper
Section 2 introduces the methodology of this project, discussing the model me-
diated transformation of the ontology to blockchain code in subsection 2.1, and
model coherence checking in subsection 2.2. The paper concludes with a sum-
mary of the contribution (i.e. subsection 3.1), an overview of the progress (i.e.
subsection 3.2), and a discussion of the limitations (i.e. subsection 3.3) in section
3.
2 Methodology
2.1 Model-Driven Architecture
This project aims at building a truthful implementation of the REA ontology in
blockchain technology. To this end a Model-Driven Architecture (MDA) [7] ap-
proach was used in which the REA ontology – and its formalisations [1] – serves
as a computation independent model (CIM). This CIM is then implemented as a
platform independent model (PIM), which is suitable for a particular implemen-
tation technology domain, while abstracting from the implementation details.
This PIM is finally transformed in a platform specific model (PSM), which cov-
ers the implementation details in the technology of choice. In this project the
PIM is a static conceptual model (i.e. existence dependency graph4 (EDG)) com-
plemented with a set of behavioural conceptual models (i.e. finite state machines
3
https://www.provenance.org
4
which is a formal subset of class diagrams
Building an executable axiomatisation of the REA2 ontology 3
(FSM)). This projects considers these static and behavioural models to be a sin-
gle PIM as the MERODE methodology explained in section 2.2 guarantees the
consistency of the EDG and FSMs. Finally, the PIM is implemented as a plat-
form specific model (PSM), which is suited for a chosen technological platform.
The JMermaid5 CASE6 tool, which is used for building the MERODE compliant
PIM in this project, is able to generate Java code, where Hyperledger Fabric7 ,
which has been chosen as the blockchain technology platform for this project,
is used for building the PSM codes (i.e. Hyperledger Fabric code, composed
of CTO, JavaScript, acl). In absence of a Hyperledger Fabric code generator
in JMermaid, the Java code is used for validating the run-time behaviour of
the model and Hyperledger Fabric code compliant with the Java code and is
produced manually. Figure 1 summarises the project approach.
CIM Resource-Event-Agent Ontology
PIM Merode Computer Aided Software Engineering
PSM Hyperledger Fabric (Java)
Fig. 1. Project approach CIM-PIM-PSM
2.2 MERODE
The MERODE methodology relies on the concept of existence dependency for
its static conceptual model (i.e. the EDG).
“The existence-dependency relation is a partial ordering on objects and object
types which is defined as follows: Let P and Q be object types. P is existence
dependent on Q if and only if the life of each occurence p of type P is embedded
in the life of one single and always the same occurence q of type Q. p is called
the dependent object (P is the dependent object type) and is existence dependent
on q, called the master object (Q is the master object type). ”[8, p.83-84]
“A more informal way of defining existence dependency is as follows: If each
object of a class P always is associated with minimum one, maximum one and
always the same occurrence of class Q, then P is existence dependent on Q. In
terms of life cycles, existence dependency means that the life of the existence-
dependent object cannot start before the life of its master. Similarly, the life of
an existence-dependent object ends at the latest at the same time that the life of
its master ends.”[8, p.83-84]
5
http://mermaid.econ.kuleuven.ac.be
6
Computer-Aided Software Engineering
7
https://www.hyperledger.org/projects/fabric
4 Laurier & Horiuchi
For example, “a hotel customer and a room object will have to be created
before a reservation object by that customer for that room can be created, and
reversely, due to referential integrity rules, the reservation object will have to be
terminated before life of the customer or the room object can be ended.” [8, p.83]
Next to existence dependency, MERODE relies on event propagation to check
the coherence of EDG and FSMs.
The event propagation rule implies that if P is existence dependent on Q,
then Q participates in each event in which P participates. In other words, each
event marked for the dependent P must also be marked for the master Q. This
can be explained as follows. When an existence-dependent object is involved in
an event, its master objects are automatically involved in this event as well. For
example, if a copy is created, the corresponding title is (implicitly) involved as
well, as we now count one more copy for this title. Similarly, a state change
of a loan, e.g. because of the return of the copy, automatically implies a state
change of the related copy and member: the copy is back on shelf and the member
has one copy less in loan. By marking each event type the dependent object type
participates in also for the master object type, all implicit participations are
made explicit, and as a result, all possible places for information gathering and
constraint definition are identified. For example, the borrow method of the class
MEMBER is the right place to update the number of copies a member has in
loan and to check a rule such as a member can have at most five copies in loan
at the same time. The borrow method of the class COPY is the right place to
count the number of times a copy has been borrowed. At implementation time,
methods that are empty because no relevant business rule or effect was identified
can be removed to increase efficiency. [8, p.115]
3 Conclusion
3.1 Contribution
This project aims at producing a platform independent model that formalises
the REA ontology8 and allows for the generation of executable code with the
help of the MERODE methodology and JMermaid tool. This project’s main con-
tribution is the formalisation of the REA ontology using existence dependency
and event propagation to expose increment, decrement and duality as the be-
havioural fundaments of the REA ontology. A second contribution of this paper
is that it formalises the REA axioms as executable finite state machines.
3.2 Progress
This project was launched with a workshop at CHUO university (Japan) in
March 2018 and continued with a workshop at universit Saint-Louis - Brussels
(Belgium) in December 2018. The approach was developed at the workshop in
Japan together with a first generation of PIMs (i.e. a set of coherent EDGs
8
which served as a computation independent model
Building an executable axiomatisation of the REA2 ontology 5
and FSMs) in JMermaid and a first generation of PSMs in Hyperledger Fabric.
A second generation of PIMs was presented and discussed at the workshop in
Brussels and a third generation of PIMs and a second generation of PSMs will
be shown at the VMBO workshop in Stockholm.
3.3 Limitations
Currently, the JMermaid tool only allows for generating Java code. Consequently,
the generated code was used to validate the EDG, OET and FSMs, testing the
behaviour of the generated Java code. After this validation, blockchain code (i.e.
Hyperledger Fabric) exhibiting the same behaviour was written manually. Full
compliance with the REA literature still needs to be validated, and mappings
with e3value and DEMO might be useful.
Acknowledgements
We would like to acknowledge Jun Azumi, and Satoshi Shimiza for their con-
tribution at the workshop held at CHUO university (Japan), and Geert Poels,
Monique Snoeck, and Graham Gal for their contribution at the workshop held at
universit Saint-Louis Brussels (Belgium), and Hugues Dumont and Geert Poels
for sponsoring the workshop in Belgium.
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