The REA-DSL: A Domain Specific Modeling Language for Business Models - Advanced Information Systems Engineering - page 256

Object Management Group's(OMG) metamodeling architecture called Meta-
Object Facility (MOF) [14]. MOF comes with a meta-meta model (M3 layer)
that allows us to define the structure, i.e. the abstract syntax, of the REA DSL
as a meta-model (M2 layer). The resulting REA DSL meta-model comprises
three interlinked views, of which we describe in detail the duality and the value
chain perspective. Due to space limitations, we do not elaborate in detail on the
third view on economic resources. However, it is important to note that economic
resources - scarce objects having utility and under control of an enterprise [15]
- may form a generalization hierarchy.

3.1 The Duality Model
The duality relationship is a core concept in REA. It links an increment in the
resource set with a corresponding decrement; where increments and decrements
must be members of two different event entity sets. In the REA ontology, the
duality relationship is characterized by the unary relationship assigned to the
concept of an economic event (see Figure 3(a)).

Duality

Transformation

Transfer

Transformation

nonConsuming
Transformation

Consuming
Transformation

nonConsumingTransformation ConsumingTransformation

E1

R1

Give Ta ke Use Produce Consume

Economic
EventSeries

Entity
Set

EntitySet

Inside1 Outside1

Stock
Flow

Economic
Event

Participation

StockFlow Participation

E4

E2

R2

E3

R5

R4

Economic
Resource

Economic
Agent

EconomicResource

EconomicAgent

R3

Economic
ResourceSeries

Inside
Agent

Outside
Agent

EconomicResourceSeries

InsideAgent

OutsideAgent

Inside2 Inside3 Outside1 Inside4 Inside5 Outside1 Inside6 Outside1

(a) Meta Model (b) Example

Fig. 3. Duality

In the REA DSL, duality becomes a core model element that serves as a
building block for further purposes. The duality meta model is depicted in Figure
3(a). Figure 3(b) presents a (rather abstract) example model - which should help
understanding the meta model concepts and to introduce the concrete syntax
and the corresponding stencils.
The duality concept applies to transfers (exchanges with external actors) and
transformations (value creation inside the enterprise). In the case of transforma-
tions we distinguish between resource-consuming and non-resource consuming
transformation . As a consequence, the meta model defines consuming transfor-
mation and non-consuming transformation as special kinds of transformation as
well as transfer and transformation as specializations of duality .