ONTOLOGY CONSTRUCTION IN PRACTICE
Experiences and Recommendations from Industrial Cases
Kurt Sandkuhl, Annika Öhgren
School of Engineering at Jönköping University, P.O. Box 1026, 55111 Jönköping, Sweden
Alexander Smirnov, Nikolay Shilov, Alexey Kashevnik
SPIIRAS, 39, 14 line, 199178 St.Petersburg, Russia
Keywords: Ontology construction, ontology engineering, experience report.
Abstract: Significant progress in ontology engineering during the last decade resulted in a growing interest in using
ontologies for industrial applications. Based on case studies from different industrial domains, this paper
presents experiences from ontology development and gives recommendations for industrial ontology
construction projects. The recommendations include (1) using defined roles in a matrix project organisation,
(2) perspectives on generalisation/specialisation strategy and ontology lifecycle phases, and (3) aspects of
user participation in ontology construction.
1 INTRODUCTION
During the last decade, significant progress was
made in development methods, engineering tools
and application environments of ontologies, which
resulted in a growing interest from industry in
applying ontologies for solving various industrial
problems. Integration with other technology areas,
like knowledge management (Nanoka and Takeuchi
1995), enterprise modeling (Vernadat, 1996), or
information systems (Scheer, 1992) is another
reason for the increasing use of semantic
technologies in industry.
This paper presents experiences and recommen-
dations for ontology construction projects with focus
on industrial application contexts. The research
approach is conceptual and argumentative based on
a number of case studies that were carried out in
industrial enterprises from different domains.
In two of these cases, recent trends in the world-
wide economy to implement new production and
marketing paradigms were clearly visible and among
the reasons for starting the ontology construction
projects. These trends indicate major shifts of the
knowledge-dominated economy: (i) shift from
“capital-intensive business environment” to
“intelligence-intensive business environment” – an
“e” mindset – and (ii) shift from “product push”
strategies to a “consumer pull” management – mass
customisation approach. (Smirnov et al., 2002). All
changes required for implementation of mass
customisation approach are connected to changes in
information factors: production systems need more
knowledge about customers and customers need
more knowledge about products (Caddy, 2000).
The remainder of the paper is structured as
follows: After a brief description of important
concepts and methods for ontology construction
(chapter 2), three industrial cases of ontology
development from different application domains are
introduced (chapter 3). Experiences and recom-
mendations are presented and discussed (chapter 4)
related to project organisation, development strategy
and user participation. Conclusions and future work
are presented in chapter 5.
2 ONTOLOGY CONSTRUCTION
Ontology construction has been subject of work in
numerous research activities. This chapter will
briefly present two aspects of ontology construction
important for the following part of the paper:
ontology representation (2.1) and ontology
development methods (2.2).
250
Sandkuhl K., Öhgren A., Smirnov A., Shilov N. and Kashevnik A. (2007).
ONTOLOGY CONSTRUCTION IN PRACTICE - Experiences and Recommendations from Industrial Cases.
In Proceedings of the Ninth International Conference on Enterprise Information Systems - ISAS, pages 250-256
DOI: 10.5220/0002384002500256
Copyright
c
SciTePress
From the many different definitions of the term
“ontology” in computer science related research,
Gruber’s proposal will be used in this paper:
“An Ontology is a formal, explicit specification
of shared conceptualization.” (Gruber, 1993).
2.1 Ontology Representation
For case 1 and 3 presented in chapter 3, we use
Protégé frames or the W3C recommendation
ontology language OWL (Web Ontology language)
to represent the ontology. An OWL ontology
consists of Individuals, Properties and Classes.
In case 2 an object-oriented constraint network
paradigm (Smirnov et al., 2006) is applied, which
supports capturing of constraints in a more
sophisticated way. The OOCN-based ontology
consists of Classes, Class Attributes (Values), Value
Domains and Constraints. The Class Instances
(Individuals) are stored separately from the
ontology. The OOCN representation can be
transformed to OWL and vice verse.
2.2 Ontology Development Methods
Previously, we have evaluated existing manual
methods for ontology construction, see (Öhgren and
Sandkuhl, 2005). The aim was to find a
methodology which fits to the requirements in small-
scale application contexts (shorten development
time; minimize need for ontology expert; etc.). Since
none of the existing methodologies fulfilled the
requirements, an enhanced methodology was
proposed. Relevant parts from different
methodologies have been combined into a new
methodology, together with some other ideas. The
enhanced methodology consists of four different
phases: requirements analysis, building,
implementation, and evaluation and maintenance.
The first phase is the requirements analysis, in
which all the formalities are specified, such as users
and uses of the ontology, purpose, knowledge
sources, etc. This should also include usage
scenarios, competency questions and answers. Also,
in order to shorten the development time, integration
of already existing ontologies should be elaborated
already at this stage.
The building phase uses a middle-out approach
and is iterative. The previously defined knowledge
sources should be used and each term should also be
described in natural language. It is natural in this
phase to include domain expert evaluation, since the
domain experts probably are involved in this phase.
The implementation phase consists of
implementing the ontology in an appropriate
ontology editor tool, which also includes choosing
the most suitable ontology representation.
Finally the ontology needs to be evaluated and
tested according to the requirements stated in the
requirements analysis. The ontology should also be
evaluated according to criteria such as clarity,
consistency, and reusability.
3 INDUSTRIAL CASES
This chapter introduces the industrial cases forming
the basis for discussion of experiences in chapter 4.
When selecting these cases, the objective was to
achieve a wide heterogeneity regarding
The type of project including research project,
applied research and contract development,
The application domain, which here
encompasses automotive industry, media
industry and industrial automation
The purpose of the ontology developed
including information structuring, model
integration and product codification.
Besides the above cases, experiences from a number
of other ontology projects contributed to this paper,
like (Smirnov, 2001), (Billig and Sandkuhl, 2002),
(Smirnov et al, 2006), (Tarasov, 2006).
3.1 Autoliv Electronics
The first industrial case was taken from automotive
industries. Automotive manufacturers and suppliers
have to manage a large number of product variations
and their integration into a specific car model. In
order to manage and control variety, manufacturers
and suppliers increasingly recognize the need to
manage project entities like models, documents,
metadata, and classification taxonomies in such a
manner that the integrative usage of these entities is
supported.
The application scenario for the ontology
developed is integration of different kinds of
structures reflecting the artefacts and their
interrelations. On the one hand, model hierarchies
have to be captured, indicated and implemented by
different modelling levels (system, software,
hardware, etc.), which furthermore will have model
instances (artifacts) to be managed. On the other
hand, term networks and taxonomies have to be
considered as equally important. These networks
represent organizational structures, product
structures or taxonomies originating from customers
that are closely related to artifacts. Explicit
denotation of these relationships are considered
ONTOLOGY CONSTRUCTION IN PRACTICE - Experiences and Recommendations from Industrial Cases
251
beneficial for identification of reuse potential of
components or artifacts.
The ontology construction was performed in a
Swedish automotive supplier of software-intensive
systems. The development process applied is an
enhanced version of the METHONTOLOGY
process as described in 2.2. Most important
knowledge sources were (1) a description of the
suppliers internal software development process
with defined procedures for all major aspects of
software development and software project
management and (2) documentation of two example
cases for requirement handling, including original
customer requirements, system and functional
requirements, and (3) interviews and working
sessions with members of the software development
department were conducted including project
manager, software developers and engineers.
The resulting ontology consisted of 379 concepts
and with an average depth of inheritance of 3,5.
3.2 Festo
The second industrial case originates from industrial
and process automation. For companies with wide
assortments of products (more than 30 000 – 40 000
products of approx. 700 types, with various
configuration possibilities) it is very important to
ensure that customers can easily navigate among
them. One solution is to provide a codification
system that can produce easily recognizable and at
the same time relatively short codes. In this section
an overview of the ontology-based approach to
designing product codes is presented. The approach
has been implemented at the industrial company
Festo that has more than 300.000 customers in 176
countries. Festo has more than 52 subsidiaries
worldwide with more than 250 branch offices and
authorised agencies in further 36 countries. A
detailed description of the approach can be found in
(Oroszi et al., 2006).
The developed approach is based on the idea that
knowledge can be represented by two levels. The
first level describes the structure of knowledge.
Knowledge represented by the second level is an
instantiation of the first level knowledge; this
knowledge holds object instances. The knowledge of
the first level (structural knowledge) is described by
a central ontology of the company's product families
(classes). In this particular case the entities are
product families. Usage of product families enables
defining product platforms that can be reused across
whole families of similar products.
In Festo case the goal was to build a problem-
oriented ontology for the given, specific purpose.
Hence it was more reasonable to build a new
ontology using the formalism that met the
requirements than to try to adapt other existing
ontology models like CYC or SENSUS. The
creation of the ontology described above was done
automatically based on existing documents and
defined rules of the model building. The resulting
ontology consists of more than 1000 classes
organized into a 4 level taxonomy, which is based
on the VDMA classification.
Taxonomical relationships support inheritance
that makes it possible to define more common
attributes for higher level classes and inherit them
for lower level subclasses. The same taxonomy is
used in the company's PDM and ERP systems.
For each product family (class) a set of
properties (attributes) is defined, and for each
property its possible values and their codes are
defined as well. The lexicon of properties is
multilingual and ontology-wide, and as a result the
values can be reused for different families.
Application of the central single ontology provides
for the consistency of the product codes and makes it
possible to instantly reflect incorporated changes in
the codes.
3.3 Jönköpings-Posten
The third application case was taken from media
industries and is focusing on a local newspaper
specialising on news from the region of Jönköping
in Sweden. In order to meet the demands of their
readers, the newspaper aims at providing not only
news and background information about events,
activities, politics or businesses in the region, but
also if local organisations or individuals are involved
in events outside the region, like a local politician
having a car accident in Stockholm or the ice hockey
team finishing on 2
nd
place at a tournament abroad.
Various information sources are used for
detecting relevant news, like different news
agencies, archives, own reporters or e-mails
containing hints from readers. The intended use of
the enterprise ontology developed is to support
evaluating, ranking and assigning the incoming
information to the reporter in charge for the
respective subject area. (Uschold and King, 1995)
name several intended uses for an enterprise
ontology, including being “communication medium”
between different people, people and computational
systems, and different computational systems. From
these intended uses, the enterprise ontology
developed for the newspaper primarily aims at
supporting communication between people.
Furthermore, Uschold and Kings recommendation to
use enterprise ontologies for integrating and relating
ICEIS 2007 - International Conference on Enterprise Information Systems
252
available information is also an important
motivation for constructing the ontology.
The development process followed the
description in section 2.2 and started by a number of
interviews at Jönköpings-Posten to get a feeling of
which were the most important terms and what
should be the focus of the ontology. In the initial
stage it was decided that the ontology should capture
regional and organisational aspects, and different
terms and concepts related to sports. Old issues of
the newspaper were analysed in order to try to
extract and find important terms and concepts and
the relationships between them.
The resulting ontology has 457 concepts, but has
not yet been evaluated thoroughly, and might be
subject for further revisions.
4 EXPERIENCES
Experiences and recommendations presented in this
chapter were based on the industrial cases
introduced in chapter 3, findings from other research
and development projects applying ontologies and
teaching ontology construction in university courses.
4.1 Project Organisation
General project management principles, like those
introduced in (Sommerville, 2004, chapter 5) should
also be applied for ontology development projects,
i.e. there should be clear and unambiguous
description of the purpose of the ontology to be
developed, a project plan including resource
allocation, milestones and deliverables should
include the complete development process, quality
control should be established independently from the
project management and be guided by a quality plan,
and resource allocation for the project should be
adequate. In addition to these recommendations,
which are valid for most project types, focus of this
section will be on project organisation for ontology
development projects.
The critical resources during the development of
ontologies for industrial purposes are from our
experience the domain experts in the companies.
Typical situation in companies is that these experts
are involved in several projects or activities and that
agreeing on meetings or workshops with them is a
difficult endeavour. An appropriate resource
allocation to the overall project solves this problem
only partly because it still is depending on the other
activities running which priority the ontology
development will be given by the superior of the
domain expert. Our recommendation is to
additionally establish a matrix organisation for the
ontology development project, i.e. for the runtime of
the project an organisation unit should be created
reflecting the project. For the required share of their
work the domain experts should then be released
from their position in the line organisation and
moved to the projects’ organisation unit, which
gives the project manager in the company better
control on how to use their time. (Jenny, 1997)
discuss additional aspects of matrix and line
organization in IT projects.
In the Autoliv case, the matrix organisation was
not established. Although both the company and the
department in question committed to support the
project, the availability of the domain experts was
not as expected due to other activities with higher
priority. The Festo case had a dedicated project team
following the matrix organisation principle resulting
in a good availability of the resources. This
difference between the projects was to some extent
of course due to the fact that one project was applied
research not financed by the company (Autoliv)
whereas the other case was contract research with
Festo as the paying customer.
Furthermore, the project team should include
several roles:
Process owner: the owner of the development
project who is responsible for establishing the
project in the company, assigning the right
personnel resources, arranging meetings, etc.
Planner: the person responsible for proposing
the way of working and establishing a
consensus between all participants, coordinator
of different tasks, moderator of meetings, etc.
Method expert: provides expert knowledge in
ontology development process and method to
the project
Facilitator: is experienced in using the selected
ontology management tool and facilitates
ontology construction
Domain expert: provide knowledge about the
domain under consideration, which is basis for
ontology development
Persons assigned to these roles from company
side, i.e. project manager and domain experts,
should be members of the projects organisation unit.
4.2 Development Process
The development process as such is governed by the
method applied (see chapter 2). Experiences with
these methods have been published earlier (see 2.2).
Additional experiences contributed by this paper
concern the identification of relevant concepts,
relation and properties or constraints. One aspect to
ONTOLOGY CONSTRUCTION IN PRACTICE - Experiences and Recommendations from Industrial Cases
253
discuss is whether to work top-down, bottom-up or
middle-out. Our impression from ontology
development projects indicates that experience from
enterprise modelling (e.g. (Vernadat, 1996))
concerning these strategies can be applied as rule of
thumb for ontology projects:
Top-down approaches should be used in
application domain well-known to the project team
where the complexity in terms of required level of
detail and the scope of the development is clearly
defined. An example from our background would be
the Festo case, where the existing codification
system, number of products and potential variation
limited the complexity of problem at hand. In cases
with unclear or unknown complexity, there is the
danger of consuming the resources allocated to the
project before reaching the goal of having developed
an ontology.
Also in projects with bottom-up development
strategy, the danger of exceeding the given time and
budget of a project is existing, if required granularity
of the ontology and complexity of the overall area
are not clear. Bottom-up can result in a number of
thoroughly defined parts of an ontology, which are
not very well interlinked and do not cover the
intended scope of the ontology. These “solution
islands” often contain more details than required for
the purpose of the ontology. Our recommendation is
to always test suitability of the bottom-up approach
by using it in a pre-study with limited scope and
clearly defined evaluation criteria.
The middle-out approaches is from our
experience suitable to explore both, complexity of
the problem at hand and required level of detail, in
application fields unknown to the ontology expert.
At the same time the middle-out way in most cases
creates results that can be used for the final
ontology. The middle-out approach was for example
used in the Jönköpings-Posten case in order to
capture sports related concepts in combination with
regional concepts. What level of detail of regional
information was needed in order to describe the
sports selection in this region in sufficient detail
became only clear during the ontology development
process.
In addition to this generalisation/specialisation
strategy, we recommend to also have different
lifecycle phases of an ontology in mind during the
development process, like
The conceptual stage where the main elements,
structures, relations and constraints of an
ontology are identified based on the knowledge
of the domain experts and other knowledge
sources. This stage should be independent from
the actual ontology representation or ontology
engineering tool to be used in order to avoid
unnecessary dependencies from implementation
technology
The implementation stage coding the result
from the conceptual stage in appropriate
representation with a suitable tool. Separation of
conceptual and implementation stage allows for
selection of the implementation technology
based on the lessons learned from the
conceptual stage
The application stage concerning the pruning
and optimisation of the implementation for the
application purpose, which for example can
include additional instances or axioms for
consistency purposes.
To distinguish between these different phases is
part of several methods, like METHONTOLGY or
the method proposed by Staab et al. (2001), who use
feasibility study/ontology-kickoff and refinement
instead of conceptual stage and implementation
stage. However, many other methods do not make
this strict distinction, which is why this paper
emphasizes the importance of clear separation.
In the Autoliv case, the decision to use Protégé
was made quite early in the development process,
i.e. the conceptual and the implementation stage
were not clearly separated. As a consequence, the
enterprise ontology developed and represented in
Protégé did require a number of compromises and
work-arounds in order to represent feature models in
this ontology. Feature models to a substantial part
include “subsumes” relations between the features,
which could not adequately be captured by the “is a”
relations in Protégé. The users of the ontology were
not satisfied with the solution and demanded a
rework. Separation between conceptual and
implementation stage would have avoided the
unnecessary iteration.
In the Festo case, the application stage is of
particular importance. Since the company
continuously introduces new products, the built
ontology has to be modified accordingly. For this
purpose the company experts were given a tool that
they successfully use. The tool is domain oriented:
the experts do not even necessarily know that they
work with the ontology.
4.3 User Participation
Since more than a decade, participative modelling is
recognised as valuable and practicable instrument
contributing to solving design problems in particular
in organisational contexts (see e.g. (Nilsson et al,
1999)). As opposed to the traditional approach of
gathering facts by interviewing stakeholders in an
organisation and afterwards developing a solution
without stakeholder involvement, the participative
ICEIS 2007 - International Conference on Enterprise Information Systems
254
way of working includes development of the
intended solution with direct involvement and
contribution of the future users, like modelling in
facilitated group sessions.
Experiences from ontology development projects
like the cases presented in chapter 3 indicate the
value of user participation even for ontology
development projects. The main recommendations
are to thoroughly prepare participation and to
concentrate on the conceptual stage of development.
To prepare user participation should start with
the key persons at the industrial company, e.g. the
head of the organisation unit in charge and the
process owner, who should be introduced to the
potentials and limits of ontologies. In many
organisations there exists the myth of ontologies as
the silver bullet for all knowledge representation
problems; in other they are considered as yet another
modelling technique. By clearly defining purpose of
the project, intended use of ontologies and known
limits, the expectation of the industrial partner
should be adjusted to realistic possibilities. This
should preferably happen before the project starts.
After sufficient management information and
attention, the intended participative steps of the
ontology development should be prepared by
individual discussions with the participants. Each
participant should be informed about the purpose of
the ontology development project and the intended
way of working. However, main purpose of these
individual discussions is to start identifying existing
knowledge sources in the organisation relevant for
the ontology development, to build up trust to the
participating users, and to increase their commitment
to the project.
During the participative parts of the ontology
construction, focus should be on the conceptual
stage of the ontology development and on use of
techniques like card sorting or pencil and paper
sketches. Main reason for this is to not put the
burden of learning and understanding the formalities
of an ontology language or the functionality of an
ontology engineering tool on the domain experts and
end users participating. A notation that everyone
understands should be used, otherwise to too much
attention is lost when the participants try to
understand the notation used.
Furthermore, the role distribution proposed in
section 4.1 should also be observed during the
participative part. In particular, the ontology expert
and the facilitator should lead the overall process
based on the selected construction methods. Too
much focus on the method or even training the
participants in method knowledge will based on our
experience distract the participants from solving the
problem at hand. The facilitator should also make
sure that the process owner does not dominate the
sessions. An important point of participatory
working is extending the view by including a wider
group of stakeholders and giving them an equal
possibility to contribute.
5 CONCLUSIONS
Based on the discussion of three industrial cases and
on results from earlier ontology construction
projects, this paper presented a number of
experiences and recommendations for ontology
construction in an industrial context. The
recommendations can be summarizes as follows:
Project organisation:
establish a matrix organisation for ontology
construction projects
Use the roles process owner, planner, facilitator,
method expert and domain expert
Development process
Use top-down development for well-known
domains with clearly defined scope
Use middle out development for unknown
application fields
Always perform a pre-study before deciding to
use bottom-up development
Clearly separate between conceptual,
implementation and application stage
User participation
Create realistic expectations on company
management side by introducing potentials and
limits of ontology use
schedule individual discussions with every
participant to prepare the participative parts
use participative work mainly in the conceptual
stage, i.e. avoid details of ontology
representation
do not train users in development method
Although the work presented in this paper is
based on quite a few industrial projects, the main
limitation of the research is that the empirical
grounding should be improved by an increased
number of cases. The recommendations presented
are considered useful, but they can not be expected
accurate for all industrial cases.
In the Festo case, the main limitation is that the
ontology built and the methodology used are not
universal but oriented to the particular problem.
However, due to usage of the OOCN formalism they
still can be used for different purposes, e.g., those
mentioned in (Oroszi et al., 2006). Besides,
compatibility between OOCN and OWL makes it
ONTOLOGY CONSTRUCTION IN PRACTICE - Experiences and Recommendations from Industrial Cases
255
possible to use the developed ontology in other
company projects.
Future work will include further elaboration on
the recommendations. We consider it interesting and
important to investigate, whether and how the
different application domains, development purposes
or project types affect project organisation,
development process and user participation, i.e. is it
possible to recommend – based on extended
empirical grounding – project organisation and
development process for enterprise ontology
development in for example automotive industry?
Furthermore, there are a number of experiences
from industrial projects not discussed in this paper
because they were just based on a single case, like
the integration of ontologies with existing IT-
systems in the companies under consideration.
ACKNOWLEDGEMENTS
Some parts of the research presented here were done
under the joint project "New Order Code" between
Festo AG & Co. KG and SPIIRAS. Elements of the
ontology-driven architecture were developed under
project # 16.2.35 of the research program
"Mathematical Modelling and Intelligent Systems",
project # 1.9 of the research program “Fundamental
Basics of Information Technologies and Computer
Systems” of the Russian Academy of Sciences, and
project funded by grant # 05-01-00151 of the
Russian Foundation for Basic Research.
Other parts of this work were financed by the
Swedish Knowledge Foundation (KK-Stiftelsen),
grant 2003/0241, project “Semantic Structuring of
Components in Model-Based Software Engineering
for Dependable Systems” and by Hamrin
Foundation (Hamrin Stiftelsen), project “Media
Information Logistics”.
Cooperation between SPIIRAS and Jönköping
University was supported by the Swedish
Foundation for International Cooperation in
Research and Higher Education under grant #
IG2003-2040.
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