=Paper=
{{Paper
|id=Vol-2195/pattern_paper_2
|storemode=property
|title=Two Ontology Design Patterns toward Energy Efficiency in Buildings
|pdfUrl=https://ceur-ws.org/Vol-2195/pattern_paper_2.pdf
|volume=Vol-2195
|authors=Iker Esnaola-Gonzalez,Jesús Bermúdez,Izaskun Fernández,Aitor Arnaiz
|dblpUrl=https://dblp.org/rec/conf/semweb/Esnaola-Gonzalez18
}}
==Two Ontology Design Patterns toward Energy Efficiency in Buildings==
Two Ontology Design Patterns toward Energy
Efficiency in Buildings
Iker Esnaola-Gonzalez1,2 , Jesús Bermúdez2 , Izaskun Fernández1 , and Aitor
Arnaiz1
1
IK4-TEKNIKER, Iñaki Goenaga 5, 20600 Eibar, Spain
{iker.esnaola, izaskun.fernandez, aitor.arnaiz}@tekniker.es
2
University of the Basque Country (UPV/EHU), Paseo Manuel Lardizabal 1, 20018
Donostia-San Sebastián, Spain
jesus.bermudez@ehu.eus
Abstract. Achieving an energy efficient operation of a building is not
a straightforward task. In this article, two Ontology Design Patterns
(ODP) are proposed, motivated by specific challenges that arise in this
domain, and with the intention to support data analysts towards this
goal. The two proposed ODPs are the AffectedBy ODP and the EEP
(Execution-Executor-Procedure) ODP, which is an extension of the first.
Both of them are intended to fill the gap that existing ontologies and
ODPs fail to address adequately. Furthermore, both ODPs are aligned to
an upper level ontology and some other related ontologies, which makes
them applicable to other domains and scenarios.
1 Introduction
Buildings and construction account for more than 35% of global energy use and
nearly 40% of energy-related CO2 emissions [1]. This is why efficient manage-
ment of building energy plays a vital role and is becoming the trend for a future
generation of buildings. Furthermore, since people spend more than 85% of their
time in buildings [2], feeling comfortable while staying indoors is a must. In
this context, the convergence of the Internet of Things’ (IoT) rapid spread and
the Knowledge Discovery in Databases (KDD) is expected to lead to significant
progress. A KDD process can be understood as a five step process to extract use-
ful knowledge from raw data and, in the energy efficiency field for buildings, they
have traditionally been employed for tasks such as energy consumption forecast-
ing [3]. However, having insufficient domain expertise can make data analysts
feel overwhelmed throughout this process, resorting to a trial-and-error approach
searching for variables and tasks to make accurate predictions. Consequently, the
KDD process becomes arduous and time-consuming.
The EEPSA (Energy Efficiency Prediction Semantic Assistant) process ad-
dresses this problem taking leverage of Semantic Technologies like ontologies,
ontology-driven rules and ontology-driven data access to guide data analysts
through the different KDD phases in a semi-automatic manner, towards the en-
hancement of the KDD process [4]. In this process, the EEPSA ontology3 plays
a vital role capturing the necessary knowledge, mainly related to buildings, sens-
ing and actuating devices, and their corresponding observations and actuations.
This knowledge, along with other relevant domain and expert knowledge for the
matter at hand, is captured in well-decoupled modules and represented in a form
that can support data analysts.
In this paper, two Ontology Design Patterns (ODP) are proposed: the Af-
fectedBy ODP and the Execution-Executor-Procedure (EEP) ODP, which is an
extension of the AffectedBy ODP. Both ODPs are motivated by specific chal-
lenges that arise in problems related to energy efficiency in buildings, and they
are defined with the intention to support data analysts throughout the KDD
process. These two ODPs form the core of the renewed version of the EEPSA
ontology. Furthermore, both ODPs are aligned to an upper level ontology and
some other related ontologies, which makes them applicable to other domains
and scenarios.
The rest of this paper is structured as follows. Section 2 introduces the related
work. Section 3 describes the two ODPs. Finally, the conclusions of this work
are presented in section 4.
2 Related Work
The energy efficiency in buildings domain spans concepts that overlap with the
IoT field such as spaces, devices, observations, procedures, properties, and units
of measurements to name a few. Some ontologies have considered these issues
in their universe of discourse. However, the intended broad scope of these on-
tologies, usually cause large and complex bodies of terminology, and sometimes
introduce too specific commitments that provoke a hard learning curve and hin-
der their reuse. An encouraging ontology design methodology to unlock these
problems is the pattern-based ontology design. An ODP is a modelling solution
to solve a recurrent ontology design problem [5]. Ideally, ODPs should be ex-
tendable but self-contained, minimize ontological commitments to foster reuse,
address one or more explicit requirements (such as use cases or competency ques-
tions), be associatable to an ontology unit test, be the representation of a core
notion in a domain of expertise, be alignable to other patterns, span more than
one application area or domain, address a single invariant instead of targeting
multiple reocurring issues at the same time, follow established modelling best
practices, and so forth [6]. Following, a quick review of ODP-based ontologies
related to sensing and actuating devices, and their context, is presented.
The DOLCE+DnS Ultralite (DUL4 ) ontology is a simplification of some
parts of the DOLCE Lite-Plus library and Descriptions and Situations ontology.
It is an upper-level ontology, and it defines general terms that are common
across different domains. Therefore, it supports a broad semantic interoperability
3
https://w3id.org/eepsa
4
http://www.ontologydesignpatterns.org/ont/dul/DUL.owl
among domain-specific ontologies by providing a common starting point for the
formulation of definitions.
The Semantic Sensor Network (SSN) ontology [7] was developed by the W3C
Semantic Sensor Networks Incubator Group (SSN-XG5 ) and described sensors,
observations and methods used for sensing among other concepts. It was aligned
with the DUL ontology and built around a central ODP called Stimulus-Sensor-
Observation [8] (SSO) describing the relationship between sensors, stimulus and
observations. The W3C Spatial Data on the Web Working Group (SDWWG6 )
proposed an update of the SSN ontology7 that became a W3C recommendation.
The new version of the SSN ontology8 follows a horizontal and vertical modular-
ization architecture by including a lightweight but self-contained core ontology
called SOSA9 (Sensor, Observation, Sample, and Actuator) for its elementary
classes and properties. Furthermore, similar to the original SSO patterns, SOSA
acts as a central building block for the new SSN ontology. In line with the changes
implemented for the new SSN ontology, SOSA also avoids the direct DUL import
that previous version had, although an optional alignment can be achieved via
the SSN-DUL alignment module10 .
The Actuation-Actuator-Effect11 (AAE) ODP intends to model the relation-
ship between an Actuator and the Effect it has on its environment through
Actuations. This pattern adapts the SSN ontology’s SSO ODP for actuators.
The new version of the SSN ontology covers the function of the AAE ODP for
actuators by expanding the SSO pattern in the SOSA ontology.
The SSN ontology does not provide enough constraints to the definitions of
classes and properties to guarantee a proper answer to a question like: what is
the feature of interest corresponding to a given property that has been observed
by a sensor? And neither to this other question: which sensors observe a given
property of a feature of interest? The patterns proposed in this paper solve these
problems.
The SmartEnv ontology, proposed as a representational model to assist the
development process of smart environments, is a network of 8 different ODPs [9].
These ODPs are used to modularize the proposed solution, while at the same
time avoiding strong dependencies between the modules to manage the represen-
tational complexity of the ontology. The SmartEnv relies on the SSN ontology
without introducing enough constraints to solve the aforementioned weaknesses
of the SSN ontology.
The SEAS Ontology[10] is an ontology designed as a set of simple core ODPs
that can be instantiated for multiple engineering related verticals. It is planned
5
https://www.w3.org/2005/Incubator/ssn/
6
http://www.opengeospatial.org/projects/groups/sdwwg
7
https://www.w3.org/TR/vocab-ssn/
8
http://www.w3.org/ns/ssn/
9
http://www.w3.org/ns/sosa/
10
http://www.w3.org/ns/ssn/dul
11
http://ontologydesignpatterns.org/wiki/Submissions:
Actuation-Actuator-Effect
to be added to the SAREF (Smart Appliances REFerence) ontology12 , which
is expected to ease its adoption and extension by industrial stakeholders, while
ensuring easy maintenance of its quality, coherence, and modularity [11]. The
SEAS Feature of Interest ontology13 , is one of the modules that forms the SEAS
ontology, and defines features of interest (seas:FeatureOfInterest) and proper-
ties (seas:Property). The Procedure Execution ontology14 (PEP) defines pro-
cedure executors that implement procedure methods, and generate procedure
execution activities. Furthermore, PEP defines an ODP as a generalization of
SOSA’s sensor-procedure-observation and actuator-procedure-actuation models.
The patterns proposed in this paper are a reengineering of the PEP and the Fea-
tureOfInterest ontologies and, additionally, an integration of them into a single
ODP.
The Observation15 ODP aims at representing observations of things, under a
set of parameters. This set of parameters may include the place where the obser-
vation was made, the time when it was made, and any other feature concerning
the specific thing being observed.
The IoT Application Profile (IoT-AP) ontology, is an ontology for represent-
ing and modelling the knowledge within the domain of the IoT [12]. The ontology
is designed re-using ODPs such as the aforementioned Observation ODP. It fo-
cuses in observations, but it also covers sensors that make those observations,
values of those observations and observation collections. However, this ontology
suffers from similar weaknesses to those previously commented about the SSN
ontology. This is basically due to the lack of proper constraints on property
definitions.
The ODP repository16 collects and makes ODPs available on the web, allow-
ing users to download, propose, and discuss them. Some of the mentioned ODPs
are hosted in this repository.
3 Motivation and Pattern Overview
The EEPSA ontology supports data analysts that are not experts in the energy
efficiency in tertiary buildings domain, towards the creation of enhanced pre-
dictive models. For that purpose, the ontology not only needs to contain both
domain knowledge and expert knowledge, but also needs to represent it in a way
that can be leveraged to guide data analysts throughout the KDD process.
In energy efficiency problems related to tertiary buildings domain, two re-
current modelling challenges arise. The first one is related to modelling variables
that may affect an indoor condition such as indoor temperature or occupancy.
The second one is related to modelling the variables measured within a building
and the systems to measure them. The definition of ODPs for these problems
12
https://w3id.org/saref
13
https://ci.mines-stetienne.fr/seas/FeatureOfInterestOntology
14
https://ci.mines-stetienne.fr/pep/
15
http://ontologydesignpatterns.org/wiki/Submissions:Observation
16
http://www.ontologydesignpatterns.org
would be beneficial and could ideally act as building blocks to be reused in case
someone else faces these same modelling challenges.
3.1 AffectedBy
In the first phase of a typical KDD process, known as the Data Selection phase,
the EEPSA process supports data analysts selecting datasets and subset of vari-
ables or data samples that are relevant for the matter at hand. Taking into
account that data analysts may not be experts in the energy efficiency in ter-
tiary buildings domain, they may feel overwhelmed during this task, due to their
lack of expertise in choosing the adequate variables. Therefore, they would ben-
efit from a resource that supports the discovery of relevant variables that affect
the environment of a given space or another feature of interest. Any of these
variables will be represented as properties or qualities of a feature of interest.
For example, let us consider the LR03 lecture room as a feature of interest: a
lecture room located on the ground floor of a building, and with a large window
that overlooks the road that passes near the building. Some properties of LR03
are: the area of the lecture room, the number of seats available or the quality
of comfort at any given time. The quality of comfort in this lecture room is
affected by the room temperature and the nearby outdoor noise. In turn, the
temperature of LR03 is affected by the number of people present in the lecture
room, the humidity of the lecture room, and the intensity of solar radiation
received through the room window. Regarding the impact of outdoor noise, it
is affected by the sound insulation factor of the room. Lastly, the received solar
radiation is affected by the azimuth (i.e. orientation) of the lecture room window.
The following competency questions must be considered:
– CQ1: What are the properties/qualities of a feature of interest?
– CQ2: What are the properties/qualities that affect a given property of a
feature of interest?
– CQ3: Which feature of interest does a given property/quality belongs to?
The SSN Ontology contains a building block that may be useful for this
matter. However, an inadequacy was spotted. The ssn:Property class is textu-
ally defined as “a quality of an entity. An aspect of an entity that is intrinsic
to and cannot exist without the entity”. This definition is made basically, ac-
cording to the definition of the dul:Quality class. In fact, it is declared17 that
ssn:Property rdfs:subClassOf dul:Quality. Furthermore, the ssn:Property class
is linked to the ssn:FeatureOfInterest class with the ssn:isPropertyOf object
property. Nevertheless, this object property is not functional, meaning that the
ssn:isPropertyOf property can have more than one value for the same individual,
so the following triples can be found in a ssn-annotated triple set:
:temperature rdf:type ssn:Property.
:temperature ssn:isPropertyOf :lr03.
17
https://www.w3.org/TR/vocab-ssn
:lr03 rdf:type ssn:FeatureOfInterest.
:temperature ssn:isPropertyOf :lr07.
:lr07 rdf:type ssn:FeatureOfInterest.
:lr03 owl:differentFrom :lr07.
According to the aforementioned ssn:Property’s class textual definition, in-
dividual :temperature is intrinsic to and cannot exist without the existence of
individual :lr03. However, the triples shown contradict such definition (i.e., :tem-
perature is a quality of different entities). Probably, designers of the SSN ontol-
ogy would advise against this practice and, in fact, example “B.3 apartment
134”18 uses the URI for referring to an
individual that represents the electrical consumption of the apartment #134.
However, the identification of the feature of interest (i.e., apartment #134) of
this property is embedded in the URI and this is not enough for machine inter-
pretation. Of course, two different rooms may have the same temperature value
(e.g. 15◦ C) but such circumstance would be represented as a property value of
each different temperature instances. Moreover, a suitable hierarchy of Property
subclasses may be desirable. A class Temperature would be a subclass of class
Property. Therefore, it could be possible to ask for all the features of interest
that have a temperature quality.
The issue mentioned above is tackled in the SEAS Feature of Interest ontol-
ogy, where an ODP to describe features of interest and their properties is defined.
In this pattern, the seas:isPropertyOf object property links a seas:Property to
a seas:FeatureOfInterest, and it is declared as subproperty of ssn:isPropertyOf.
However, seas:isPropertyOf is functional. Therefore, it represents more faithfully
the textual definition of ssn:Property.
Furthermore, the SEAS Feature of Interest ontology also defines the seas:de-
rivesFrom object property which links a seas:Property to another seas:Property
it derives from. This object property is defined as a symmetric property, which
means that the property has itself as inverse. However, this constraint is un-
necessary and sometimes even inappropriate. For instance, the temperature of
individual :lr03 may derive from the occupancy of the room, but the occupancy
does not necessarily derive from the temperature of the room.
In addition, the SEAS Feature of Interest ontology contains a textual com-
ment that, although relevant, it is not materialized as an axiom:
seas:hasProperty