Challenges of Modeling and Evaluating the Semantics of Technical
Content Deployed in Recommendation Systems for Industry 4.0
Jos Lehmann, Michael Shamiyeh and Sven Ziemer
Bauhaus Luftfahrt e.V., Willy-Messerschmitt-Straße 1, Taufkirchen, 82024, Germany
Keywords:
Modeling, Evaluation, Deployment of Semantics, Web Ontology Language, Industry 4.0, Aviation.
Abstract:
In the context of Industry 4.0 the Smart Factory is enabled by the automation of physical production activities.
The automation of intellectual pre-production activities enables what is here dubbed the “Smart Studio”. A
key-element of the Smart Studio is Semantic Technology. While prototyping an ontology-based recommen-
dation system for technical content about the case-study of the aviation industry, the problem of the readiness
level of Semantic Technology became apparent. This led to the formulation of a Semantic Modeling and Tag-
ging Methodology. The evaluation of both prototype and methodology yielded valuable insight about (i) the
quantity and quality of semantics needed in the Smart Studio, (ii) the different interaction profiles identified
when testing recommendations, (iii) the efficiency and effectiveness of the methods required to achieve se-
mantics of right quantity and quality, (iv) the extent to which an ontology-based recommendation system is
feasible and reduces double work for knowledge workers. Based on these results in this paper a position is
formulated about the challenges for the viable application of Semantic Technology to technical content in
Industry 4.0.
1 INTRODUCTION
Research on Industry 4.0 develops and evaluates soft-
ware prototypes to assess how and to what extent dig-
ital technology can make industrial processes more
flexible and efficient (Vogel-Heuser et al., 2017). As
discussed in (Lehmann et al., 2017) and in (Lehmann
et al., 2018), digital technology can potentially ef-
fect two new paradigms: the Smart Factory, an es-
tablished concept in research on Industry 4.0, and
what, by analogy, can be dubbed the “Smart Studio”.
In the Smart Factory Robotics, Cyber-physical Sys-
tems (CPS) and the Internet of Things (IOT) can en-
able the automatic reconfiguration of Production and
Logistics lines, increasing productivity and reduc-
ing costs. In the Smart Studio Knowledge Manage-
ment (KM) and Artificial Intelligence (AI) can reshape
pre-production processes, from Conceptual Design to
Prototyping, by supporting or automating the intellec-
tual activities that make enterprise knowledge avail-
able when relevant a goal comparable to what pur-
sued in Knowledge-based Engineering and Ontology-
based Design (Li and Ramani, 2007).
A key-element of both the Smart Factory and the
Smart Studio is Semantic Technology (ST) (Biffl and
Sabou, 2016). The use of semantics in the Smart Fac-
tory is characterized by a focus on physical activities.
Here observations through sensors can be leveraged in
order to update and correct derivations about a given
state of affairs. The use of semantics in the Smart
Studio, on the other hand, cannot rely on sensing. It
therefore has to rely to a larger extent on logical in-
ference, reasoning or other forms of association, in
order to harmonize and integrate information sources
about multidisciplinary subjects (e.g. textual corpora,
model data, expert knowledge) and to flesh out im-
plicit meanings and consequences.
At present it is unclear how easily semantic tech-
nology, especially its modeling tools, can help estab-
lish the new work flow of the Smart Studio. In (Xu
et al., 2018) this point is made more generally for
many of the technologies that are being applied in
research on Industry 4.0 and that lack the required
readiness level.
While prototyping an ontology-based recommen-
dation system for technical content about the case-
study of the aviation industry, intending to test to
what extent this type of system is feasible and whether
it reduces double work for knowledge workers, the
problem of the readiness level of Semantic Technol-
ogy became apparent. This led to breaking down this
problem into a number of sub-problems (discussed
Lehmann, J., Shamiyeh, M. and Ziemer, S.
Challenges of Modeling and Evaluating the Semantics of Technical Content Deployed in Recommendation Systems for Industry 4.0.
DOI: 10.5220/0008348503590366
In Proceedings of the 11th International Joint Conference on Knowledge Discovery, Knowledge Engineering and Knowledge Management (IC3K 2019), pages 359-366
ISBN: 978-989-758-382-7
Copyright
c
2019 by SCITEPRESS Science and Technology Publications, Lda. All rights reserved
359
in Section 2 of this paper) about the modeling and
evaluation of semantics when deployed in the Smart
Studio. This in turn led to the formulation of a Se-
mantic Modeling and Tagging Methodology (Section
3). The evaluation of both prototype and methodol-
ogy (Section 4) yielded valuable insight about (i) the
quantity and quality of semantics needed in the Smart
Studio, (ii) the different interaction profiles that may
be identified when testing recommendations, (iii) the
efficiency and effectiveness of the methods required
to achieve semantics of right quantity and quality,
(iv) the extent to which an ontology-based recommen-
dation system is feasible and reduces double work for
knowledge workers. Based on these results in Section
5 a position is formulated about the challenges for the
viable application of Semantic Technology to techni-
cal content in Industry 4.0.
2 HYPOTHESES, PROTOTYPE,
PROBLEMS
Research on the Smart Studio usually assumes that
the automated fostering of enterprise knowledge is
both possible and essential to increasing the produc-
tivity of knowledge workers. In order to pin down and
partly test this assumption research hypotheses RH1
and RH2 were formulated.
RH1. It is technically feasible to implement an
ontology-based recommendation system (OBRS) that
provides in real time references to legacy data to
knowledge workers as they compile new technical re-
ports.
RH2. An OBRS increases the knowledge workers’
productivity by supporting the reuse of existing
knowledge and avoid double work.
Despite existing successful examples of ontology-
based recommendation systems in many domains, the
emphasis of RH1 is on the ontological integration
of technical content. This type of content is highly
structured and detailed, making it more challenging
to strike the right balance between the abstraction re-
quirements of ontological integration and the level of
precision required by the users of technical content.
In order to test RH1 and RH2 the design, imple-
mentation and evaluation of the prototype PR1 was
undertaken:
PR1. A prototype OBRS that provides in real-time ref-
erences to legacy technical data to knowledge work-
ers of an aviation firm as they compile in a text editor
new technical reports about aircraft components. The
prototype is developed around an existing linguistics-
and statistics-based recommendation engine, origi-
nally designed for recommendations of short non tech-
nical text items. The transition to a OBRS for technical
content is accomplished by semantic-linguistic mod-
eling and tagging, not by re-engineering the recom-
mendation engine.
PR1s development was based on the generic ar-
chitecture for multilingual semantic applications sup-
porting enterprise knowledge reuse shown in Figure
1. As reported in (Lehmann et al., 2018) with the
same formulation but more detail, the architecture
comprises four main phases (the alternating gray ver-
tical bars, read left to right).
Raw Data Acquisition. Textual data, e.g. PDF files
of technical reports and related non-textual data, e.g
STEP files of component models, are selected for in-
tegration.
Semantic Modeling. Raw data are sampled in order
to extract domain knowledge and compile ontological
structures that enable semantic tagging.
Linguistic-Semantic Integration. Textual data are
tagged based on term frequency of terms described
in the ontology. The ontology is also used to semi-
automatically tag non-textual data. All tagged data
are then stored in a database.
User Interaction. The database is dynamically ac-
cessed by a text editor to provide end-users with rec-
ommendations of existing reports or models that may
contain information that is relevant to the contents be-
ing typed in.
(Chen and Wu, 2008) discusses an architecture for
a comparable class of document recommendation sys-
tems, though based to a larger extent on user prefer-
ences rather than semantic modeling.
Working on PR1 raised two groups of problems
about the scaling-up of established approaches to data
integration. On the one hand, data-related problems
(DP1 through DP6 below) had to do with the optimiza-
tion of software components that, as shown in Fig-
ure 1, are located in the parts of the architecture, that
support the preparation and enrichment of the tens of
thousands of documents available to the OBRS plug-
in. Although not further discussed in this paper the list
of these problems provides some context on issues of
data preparation required by an OBRS.
DP1. Large Quantity of Documents.
DP2. Layout of Documents.
DP3. Large Size of Documents.
DP4. Integration of additional and relevant Metadata
avalaible to Data Owner.
DP5. Suitable Client-Server Architecture.
KEOD 2019 - 11th International Conference on Knowledge Engineering and Ontology Development
360
Figure 1: Architecture of multilingual semantic application, OBRS PR1, supporting enterprise knowledge reuse.
DP6. Connection to Data Sources.
On the other hand, semantics-related problems
(SP1 through SP7) surfaced in various parts of the ar-
chitecture shown in Figure 1. They in large part had
to do with providing the OBRS plug-in with semantics
of the right quality in the right quantity.
SP1. Coverage of the Domain Knowledge required
by the Use Cases.
SP2. Representation of the High Level of Detail of
the Vocabulary of the Model Data.
SP3. Representation of the Lexical Variations and
Multilingualism of the Documents.
SP4. Extraction of Large Quantities of Knowledge.
SP5. Ontology Reusability.
SP6. Semantic Tagging of Textual Data.
SP7. Semantic Tagging of Model Data.
3 SEMANTIC MODELING AND
TAGGING
As reported in (Lehmann et al., 2018) the engineer-
ing of appropriate ontologies requires to accurately
model the information ecosystem in which the OBRS
is meant to operate. On the one hand, a normative
modeling approach makes sure that documents are
correctly classified with respect to the domain of ref-
erence. On the other hand, when deploying an ontol-
ogy onto the corpus, issues specific to the corpus in-
terfere with correct interpretation: lexical variations,
multilingualism, abbreviations, technical data.
Figure 2 presents an updated version of the
methodology introduced in (Lehmann et al., 2018),
which supports the transition of information from
sample data to an ontology. After sampling a de-
scriptive document, e.g. a nomenclature for a landing
gear extension/retraction system, a conversion into
a spreadsheet takes place in step SM2a. Then, the
contents (found in headers, lists, indexes, tables etc.)
are classified as individuals of a minimal number of
classes (e.g., system, component, part) and ordered
by an hyponym property (e.g., narrower-than). For
instance, the individual of class component retrac-
tion actuator is narrower-than, i.e. an aspect of or
a functional part of, an individual landing gear exten-
sion/retraction system of class system. In turn such
system is narrower-than, i.e. an aspect of or a func-
tional part of, individuals nose landing gear resp.
main landing gear of class component. Finally, these
components are aspects of an individual of class mas-
tersystem, which classifies the most generic systems
for inferential convenience. Similarly, classes mas-
tercomponent and masterpart group the most generic
components resp. parts.
The resulting hierarchy mixes-up class/subclass,
class/instance, whole/part hierarchies, which are dis-
entangled in step SM2(b)iD. After ontological checks
and name assignments (SM2(b)i to SM2(b)iii), the
OWL ontology (DOCO-R) is set-up via a mapper.
Challenges of Modeling and Evaluating the Semantics of Technical Content Deployed in Recommendation Systems for Industry 4.0
361
SM1. Sample Data
sample reports and design models that are relevant to use-
cases
SM2. Master-Spreadsheet
(a) Prepare Sources
export content of existing multilingual documentation (such
as pdf files of reports as textual data, spreadsheets of com-
ponent hierarchies generated from design models as non-
textual data) into a spreadsheet and delete irrelevant parts
(b) Create Ontology’s Basic Version
i. Ontological Modeling
first version of ontology is created in reified form
A. Create Classes and Hyponym Property
from sources’ section names, table headers
B. Create Individuals
from sources’ section content, table entries
C. Assert Hyponym Property between Individuals
from sources’ section content, table entries
D. Qualify Hyponym Property between Individuals
disentanglement of relationships class/subclass,
class/instance, whole/part
ii. Ontological Checks
A. Translate Individuals IRI’s
into main language of ontology
B. Find Duplicate Individuals
as exact match, partial match, no match
iii. Assign names to Individuals as Annotations
including synonyms, abbreviations, their grammatical
variations (plural, cases)
SM3. OWL Ontology
(a) Export ontology
from Master Spreadsheet to DocO-R
(b) Integrate ontology
i. Abstract Individuals to Classes
from DocO-R to DocO-A
ii. Match Classes
between DoC-A and DesO-A resulting in
AviO-A
iii. Reify Classes to Individuals
from AviO-A to AviO-R
(c) Assess Coverage of Ontology
(d) Merge Ontology
(e) Export Ontology
SM4. Semantic Tagging
(a) Textual Data Enrichment
(b) Data Model Integration
Figure 2: Semantic Modeling and Tagging Methodology.
(a) AviO-A (b) AviO-R
Figure 3: Retraction Actuator in AviO.
KEOD 2019 - 11th International Conference on Knowledge Engineering and Ontology Development
362
DOCO-R is then abstracted as DOCO-A via a con-
version function, which outputs a representation of
the domain knowledge, which exploits the full po-
tential of DESCRIPTION LOGIC (DL) and does away
with classes such as mastersystem, mastercomponent,
masterpart, introduced in the reified version of the
ontology for inferential convenience. In DOCO-A
the appropriate parts of the contents of DOCO-R are
converted into a DL class hierarchy, while the rest is
represented by appropriate object or data properties.
DOCO-A can be matched with relevant ontologies,
e.g. a Design Ontology DESO-A, to get to a version
that is called Aviation Ontology (AVIO-A in Figure
3a). In this example the class aircraft of DOCO-A is
matched with the class Aircraft of DESO-A thereby
acquiring a part-of relation to the class Fuselage of
DESO-A, not found in the original sample data, given
their focus on the extension/retraction system under
consideration. AVIO-A is then reified as AVIO-R,
shown in 3b. AVIO-R reduces the number of proper-
ties and classes, reducing the expressivity of the on-
tology, while retaining all annotations.
Both conversions (Abstract, Reify) are akin to
so-called meta-modeling techniques presented for in-
stance in (Welty, 2006), (Glimm et al., 2010), (Jek-
jantuk et al., 2011).
Steps SM3c through SM3e involve checks of
AVIOs coverage with respect to external knowledge
sources, as well as the transformation of its import
structure and of its serialization, to enable its use by
the tagging modules. These steps are not further dis-
cussed in this paper.
Finally, AVIO-R is used by the Semantic Tex-
tual Data Enrichment module to integrate the term-
frequency-based tagging of the documents with extra
tags derived from the hyponym hierarchy. AVIO-A is
used by the Semantic Data Model Integration module
to provide an expert user of the Data Model Extrac-
tion & Management module (not shown in Figure 1)
with semantic tags for the non-textual data.
4 EVALUATION
The evaluation of PR1 was based on (i) user feed-
back given through questionnaires, (ii) screen shot se-
quences of user interactions that included the assess-
ment by users of the relevance of recommendations,
(iii) interviews, (iv) developer feedback given through
reporting. All this provided evidence on the following
issues:
1. How do PR1s quantity of semantics (in terms
of domain coverage) or quality of semantics (in
terms of level of detail or of lexical variations)
score on the following scale?
[too poor, poor, ok, rich, too rich]
Note that values poor and rich can either have a
positive or a negative connotation, therefore too
poor resp. too rich are used to indicate a value
beyond what is considered practical by the evalu-
ator.
2. Which types of interaction can be observed be-
tween PR1 and its users and how productive are
such interactions?
3. How do the methods described in Figure 2 score
on the following scales?
[partially efficient, efficient]
[partially effective, effective]
These scales are intended for the assessment of
the amount of effort needed (efficiency) when ap-
plying a given method for the solution of a seman-
tic problem i.e. for modeling the minimal amount
of knowledge required by the use cases of a OBRS
(effectiveness).
4. Does the evaluation of points 1 through 3 above
confirm PR1’s feasibility (RH1) and its role in
reducing double-work for knowledge workers
RH2)?
4.1 Evaluation of Semantics in PR1
As shown in Table 1 the quality (in terms of domain
coverage) and the quantity (in terms of level of detail
and lexical variations) of the semantics of PR1 was
evaluated from the perspectives of three stakehold-
ers: the ontology developer, the plug-in developer, the
plug-in user.
The coverage of the domain knowledge required
by the use cases was evaluated as ok by the ontol-
ogy developer and the end user but poor by the plug-
in developer. The ontology developer was satisfied
by the amount of domain knowledge provided to PR1
by sampling representative documents. The end user
did not notice obviously lacking semantic tags among
those the OBRS plug-in provided with any given rec-
ommendation – although the end user did not always
agree with some tags that were used for a recommen-
dation. The plug-in developer who, as opposed to
the plug-in user, had direct access to the ontology,
expected more domain knowledge to drive the rec-
ommendation engine, beyond what was harvested by
sampling the data pool.
The representation of the high level of detail of
the vocabulary of the model data was rich for the
ontology developer, because such data provides a lot
of information about class and part-of hierarchies for
Challenges of Modeling and Evaluating the Semantics of Technical Content Deployed in Recommendation Systems for Industry 4.0
363
Table 1: Evaluation of semantics in PR1.
Semantics View of View of View of
Problem Ontology Plug-in Plug-in
Developer Developer User
Coverage of
ok poor ok
Domain
Knowledge
SP1
Representation
rich too rich too rich
of Detail Level
of Model Data
SP2
Representation
ok poor n/a
of Lexical
Variations
SP3
components, down to their smallest and most com-
mon parts (e.g. O-Ring). From the perspectives of
both the plug-in developer and user this level of detail
was too rich, i.e. problematic, because the list of
recommendations could at times be clogged with rec-
ommendations that were irrelevant despite containing
many occurrences of a term, e.g. O-Ring, which ap-
peared in the input text and was very frequent in the
data pool.
Finally, the representation of the lexical varia-
tions and multilingualism of the documents varied:
for some entities in AVIO lexical variations of their
names was evaluated as rich, having been modeled
extensively, while for other entities the lexical vari-
ation was poor. This led to some dissatisfaction on
the plug-in developer’s part again based on the expec-
tation of as much structure as possible to drive the
recommendation engine.
4.2 Interaction Profiling
The relevance assessment of recommendations by the
users allowed to identify the interaction profiles de-
scribed below.
Unaimed search-Experimental tester (UE): In this
type of interaction the OBRS users saw the sys-
tem as a means to understanding more about a
theme and to finding documents beyond what
they already knew or expected as recommenda-
tions given the text they input. Users might not
always be satisfied with the recommendations
especially regarding the ontological or linguistic
categories used by the system to tag a given doc-
ument. They appreciated though the interaction
with a system that helps to explore the data pool.
Frequency: 30%
Aimed search-Prudent tester (AP): In this type of in-
teraction users similarly to UE interactions saw
the system as a means to exploring the data pool,
aiming though at getting a specific document high
up in the recommendation list.
Frequency: 10%
Very aimed search-Conservative tester (VC): In this
type of interaction users saw the OBRS from the
standpoint of their usual way of working. They
sought recommendations through a controlled in-
teraction with the system, i.e., they often typed
in just the name of a specific report, a part num-
ber, a single concept or even only an acronym in
order to test whether the system was able to de-
liver a very specific document they expected. In
these interactions users were interested in testing
whether the system could perform as well as a
user who, based on expertise and knowledge of
the data pool, knows exactly what to look for and
how to find it.
Frequency: 60%
In general, users who preferred VC interactions eval-
uated PR1 less favorably than users who preferred UE
and AP interactions. In this respect, the increase in
productivity yielded by avoiding double work seems
to be more readily available to users who are ready to
invest time in exploring the data pool through the rec-
ommendation list – either because they are interested
in exploring new aspects of the data pool to avoid du-
plication of effort or because they lack expertise and
are uncertain which existing documents they need for
a given task.
4.3 Evaluation of Methods
As shown in Table 2 the modeling and deployment
methods employed for the semantics of PR1 was
mainly evaluated from the perspective of the ontol-
ogy developer.
Sampling textual and non-textual data has proven to
be an efficient way of achieving the minimal cov-
erage and level of detail required by the use cases.
The first two rows of Table 1 suggest though that sam-
pling can only bring so far in terms of a satisfactory
behavior of an OBRS. As the number of use cases han-
dled by the system grows, more ontological modeling
is needed to semantically consolidate the system.
Assigning names to individuals as annotations for lex-
ical variations is effective, as it increases the sys-
tem’s reach on the data pool with limited ontological
modeling. As opposed to ontological modeling, an-
notating the ontology is still time-consuming though
and more likely to create redundancies.
Tabulating and mapping for knowledge extraction is
very efficient, as spreadsheets provide a first cut
of the ontology in a format in which it is easier than
KEOD 2019 - 11th International Conference on Knowledge Engineering and Ontology Development
364
Table 2: Evaluation of methods for handling semantics.
Method View of View of
for Problem Ontology Plugin
Developer Developer
Sampling for efficient,
n/aCoverage and Detail partially
SM1 for SP1, SP2 effective
Annotating partially
n/afor Lexical Variations efficient,
SM2(b)iii for SP3 effective
Tabulating and Mapping efficient,
n/afor Knowledge Extraction partially,
SM2 for SP4 effective
Abstraction and Reification partially
n/afor Reusability efficient,
SM3(b)i SM3(b)iii for SP5 effective
Textual Data Enrichment efficient, efficient,
for Semantic Tagging partially effective
SM4a for SP6 effective
Data Model Integration partially
n/afor Semantic Tagging efficient,
SM4b for SP7 effective
in ontology editors to sort and to identify explicit or
semi-implicit duplicates in the sample data. Tabula-
tion is not effective for more advanced modeling
and does not support the logical checks provided by
ontology editors.
Abstraction and reification are effective ways of
achieving reusabilty of semantic modeling results,
when starting from sample data and a hyponym-type
of relation. On the other hand, implementing and
maintaining the abstraction and reification conversion
procedures is time-consuming and requires non trivial
ontological choices.
The two semantic tagging methods employed on tex-
tual resp. non-textual data have complementary ef-
ficiency and effectiveness. SM4a can rely on a high
degree of automation because it is based on Natural
Language Processing and on term frequency, yielding
results though that do not always effectively mirror
the core semantics of a given document. Conversely,
SM4b is driven by user interaction thereby tagging
component models more effectively, at the cost of
time consuming tagging sessions.
4.4 Evaluation of RH1 and RH2
The overall evaluation of problems DP1 through DP6
(not discussed in this paper) and SP1 though SP7
allowed to establish that PR1 is technically feasible
(RH1) and that the PR1 improves the productivity of
knowledge workers (RH2). PR1 is most effective in
helping knowledge workers to learn about the seman-
tic structure of the data pool as well as about the po-
sition of single documents within that structure.
5 CONCLUSION
Work on the development and the evaluation of PR1
has helped identify a number of challenges for the vi-
able application of semantic technology in Industry
4.0.
On the one hand, many of the steps that allow for
the preparation and consolidation of semantic struc-
tures for a given organization (e.g. the steps described
in Figure 2) should be integrated in normal, day-to-
day Knowledge Management activities. Organiza-
tions that undertake the transition to a paradigm like
the Smart Factory or the Smart Studio need to develop
the necessary expertise to be able to assess the opti-
mal ratio between effort and semantics quantity and
quality when deployed in recommendation or other
computing systems. These Knowledge Management
activities should be supported by the automation of
the following functionalities:
1. Knowledge extraction in a tabular format (e.g. a
spreadsheet), rather than in an ontology editor, to
make it easier to bootstrap ontologies from sam-
ple data by operating (sorting, filtering, match-
ing, editing) on a large amount of raw input in-
formation. This is needed in order to make a se-
mantic structure specific to its context of use and
enable its deployment in a specific information
eco-system. An OWL editor becomes essential at
the later stages of ontological analysis, refinement
and general management of a consolidated ontol-
ogy.
2. Meta-modeling, i.e. (class) abstraction and reifi-
cation to learn and reuse ontologies.
3. Automated matching and automated coverage as-
sessment, to enrich ontologies.
4. Gold standard preparation of a representative sub-
set of the data pool through systematic semantic
tagging, to enable the user-independent evaluation
of ontology-based systems.
5. Automated monitoring of user-interactions, to
achieve a behavioral definition of the values in the
scales used in Section 4 (e.g. too poor, poor,
etc.) and of the interaction profiles.
On the other hand, the end-user needs to be sup-
ported in the interaction with the recommendations by
means of the following functionalities:
6. Explanations of the recommendations with re-
spect to the input text.
7. Migration of OBRS to applications other than text-
editors.
8. Configuration of queries relative to user profile or
function in the organization.
Challenges of Modeling and Evaluating the Semantics of Technical Content Deployed in Recommendation Systems for Industry 4.0
365
ACKNOWLEDGMENTS
The project underlying this
research (EFFPRO 4.0 In-
tegration and Analysis of De-
sign and Production Data for
a more efficient Development
Process Chain) has received
funding from the German
Federal Ministry for Economic Affairs and Energy
under grant agreement no. 20Y1509E.
Ontology editing and presentation in Prot
´
eg
´
e
http://protege.stanford.edu, US NIGMS/NIH grant
no. GM10331601.
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