=Paper= {{Paper |id=Vol-1449/saoa2015-6 |storemode=property |title= Redefinition and Statistical Analysis of Measures for Evaluating the Quality of Ontologies. |pdfUrl=https://ceur-ws.org/Vol-1449/saoa2015-6.pdf |volume=Vol-1449 |dblpUrl=https://dblp.org/rec/conf/jaiio/TibaldoWTRG15 }} == Redefinition and Statistical Analysis of Measures for Evaluating the Quality of Ontologies. == https://ceur-ws.org/Vol-1449/saoa2015-6.pdf
                Redefinition and Statistical Analysis of Measures
                   for Evaluating the Quality of Ontologies

                 Melina Tibaldo1 , Alexia Wilkinson1 , Ma. Laura Taverna1 , Mariela Rico1 , and
                                               Ma. Rosa Galli2
                    1
                         Centro de Investigación y Desarrollo de Ingenierı́a en Sistemas de Información
                          (CIDISI) - Universidad Tecnológica Nacional - Facultad Regional Santa Fe,
                                     Lavaise 610 - S3004EWB - Santa Fe - SF - Argentina
                                                    mrico@frsf.utn.edu.ar
                        2
                           INGAR-UTN-CONICET, Avellaneda 3657, S3002GJC Santa Fe, Argentina



                           Abstract. OntoQualitas is a framework to evaluate an ontology whose
                           purpose is the interchange of information between different contexts.
                           However, the framework does not propose acceptance thresholds of the
                           measure values. In this paper, measures proposed in this framework are
                           redefined in order to improve their usefulness in assessing the quality of
                           such ontologies. These measures were calculated semi-automatically on
                           a set of ontologies and its results were described by means of a statistical
                           analysis as a first step to the definition of their acceptance thresholds.

                           Keywords: ontology quality, measure, statistical analysis


                1       Introduction

                Even after more than a decade since the emergence of ontologies in Computer
                Science and with its growing use in different disciplines, standardized methods
                have not been developed for evaluating their quality [8].
                    Although methodologies, methods, techniques, and software tools to sup-
                port the ontology building process were proposed, ontology evaluation still plays
                only a passive role in ontology engineering projects [17]. In order to assess the
                ontology quality, different works have emerged depending on the kind of ontolo-
                gies being evaluated and for what purpose [1, 3, 5–7, 9, 15, 20–22]. These works
                present different quality measures and evaluate some ontologies quantitatively.
                However, specific studies have not been found about the suitable values of these
                measures, their acceptance thresholds, and their impact on the quality of the
                evaluated ontologies.
                    Quality is not a property of something, but a judgment, so that should be in
                relation to some purpose [6]. While issues such as orphan classes or consistency
                in naming are important, the purpose for which the ontology is developed should
                guide the evaluation of quality thus contributing to the enrichment of its quality.
                The set of measures and their corresponding weights should be in relation with
                the purpose of the ontology [15].




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Redefinition and Statistical Analysis of Measures for Evaluating the Quality of Ontologies




                      A proposed framework to evaluate an ontology considering its specific pur-
                  pose is OntoQualitas, which includes known measures and new measures to
                  evaluate the quality of an ontology whose purpose is the interchange of infor-
                  mation in a collaborative business processes environment [15]. To this aim, a set
                  of requirements is identified that the ontology should fulfill and, associated with
                  them, it is identified a set of questions that reflect specific aspects relevant to
                  the evaluation of ontology. For each question, appropriate measures, their ranges
                  of possible values, and the optimal values are defined. However, the framework
                  does not propose acceptance thresholds of the measure values.
                      In order to advance in the definition of these thresholds and their impact on
                  the ontology quality, the definition of the proposed measures should be analyzed
                  and, if necessary, modified to ensure their homogeneity. Then, it is necessary to
                  calculate the measures on a set of ontologies and conduct a descriptive statistical
                  analysis of the redefined measures in order to study their behavior.
                      This paper presents the reformulation of some of the measures outlined in
                  OntoQualitas, resulting in measures that will be more convenient for evaluation
                  of the ontology quality. In addition, a statistical study of a set of ontologies is
                  shown, to whom the reformulated measures were calculated.
                      The paper is organized as follows: Section 2 describes the main characteristics
                  of the OntoQualitas framework; Section 3 presents the reformulated measures;
                  Section 4 presents the results of the preliminary analysis of data. Results are
                  discussed in Section 5, which also includes the conclusions of this work.


                  2    OntoQualitas

                  OntoQualitas is a framework to evaluate the quality of an ontology whose pur-
                  pose is the interchange of information between different contexts [15]. It is struc-
                  tured from an overall requirement imposed on ontologies regarding its content
                  and structure, which is that the ontology should allow the interchange of infor-
                  mation between different contexts without imposing a global meaning of such
                  information to all involved contexts. From this overall requirement, three spe-
                  cific requirements are derived: (i) the representation of information interchanged
                  should be formal, (ii) only the information strictly necessary for the interchange
                  must be represented, and (iii) the representation must allow a correct interpre-
                  tation of the interchanged information in all involved contexts.
                      The second requirement aforementioned has two aspects: completeness and
                  conciseness. The third requirement has three aspects: semantic correctness, syn-
                  tactic correctness, and representation correctness, which is assessing the quality
                  of mappings of entities, relations, and features into the elements of the ontology.
                      OntoQualitas specifies questions that help addressing relevant aspects for
                  ontology evaluation. For each question, appropriate measures are associated.
                  Some of them have been proposed with the objective of assessing the quality of
                  ontologies from a quantitative perspective [3, 5, 6, 20, 21]; others were proposed
                  with the aim of evaluating the mapping between domain entities, its relationships
                  and features, and the elements used for its representation [13].




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Redefinition and Statistical Analysis of Measures for Evaluating the Quality of Ontologies




                  3    Analysis of Measures

                  In OntoQualitas, the value of some measures is provided in the range [0, 1],
                  others are provided in the range [0, n], some optimal values are 1, and others are
                  0. In order to quantify the different quality aspects and to compare values among
                  ontologies, it is necessary to homogenize the value ranges and optimal values of
                  the measures associated with each aspect. As a consequence, a first activity was
                  to modify the definition of some measures to ensure that all have the same scale
                  ([0, 1]) and optimal value (1). Additionally, some measures can only be calculated
                  if the considered ontology has the corresponding characteristics. These situations
                  are explicitly identified in Tables 1 to 5.
                       Completeness (Table 1) refers to the extension, degree, amount or coverage
                  to which the information in a user-independent ontology covers the information
                  of the real world [11].
                       Concise (Table 2) refers to whether an ontology does not store any unnec-
                  essary or useless definitions, if explicit redundancies do not exist between def-
                  initions, and redundancies cannot be inferred using other definitions and ax-
                  ioms [11].
                       Syntactic correctness (Table 3) tries to evaluate the quality of the ontology
                  according to the way it is written, i.e. the correctness and breadth of syntax
                  used [5].
                       Semantic correctness (Table 4) deals with the vocabulary used to represent
                  entities, relations, and features, and the correctness of the representation of the
                  interchanged information in the ontology.
                       Representation correctness (Table 5) is related to the quality of mappings of
                  entities, relations, and features into the elements of the ontology evaluated.


                  4    Results of Preliminary Analysis of Data

                  The results of this preliminary analysis are presented according to the second
                  and third requirements. Since the considered ontologies are formalized in OWL2,
                  the representation of information interchanged is formal, thus achieving the first
                  requirement.
                      In order to evaluate reformulations to the OntoQualitas measures, ontologies
                  for information interchange between different contexts were needed. A set of
                  ontologies created by students from the course “Development of ontology-based
                  information systems” have been developed from the same specific instructions.
                  First, ontologies (called “base”) were developed by using an ontology learning
                  technique. Then, the representation of entities, their relationships and features
                  were enriched, using a proposed method [14]. These ontologies were called “en-
                  riched”. Measures were calculated semi-automatically and the instructions were
                  the frame of reference.
                      In the base ontologies, certain measures could not be calculated due to lack of
                  the corresponding characteristics. Therefore, in the subsequent statistical anal-
                  ysis, the amount of data varies.




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Redefinition and Statistical Analysis of Measures for Evaluating the Quality of Ontologies




                                                    Table 1. Completeness measures
                   Measure
                   Necessary and sufficient conditions [11]                                           N SC = N SLC/LC
                   N SLC: Number of leaf classes with at least one set of necessary and sufficient conditions
                   LC: Number of leaf classes
                   The ontology should have at least a class hierarchy, without considering the root class (Thing)
                   Existential and universal restrictions [11]                                     EU R = EU RP/U RP
                   EU RP : Number of properties with existential and universal restrictions along the same property
                   U RP : Number of properties with universal restrictions
                   The ontology should have at least a property with an universal restriction
                   Domains and ranges of relations [11]                                    DRR = N HRDR/N HR
                   N HRDR: Number of non-hierarchical relations with domain and range specified
                   N HR: Number of non-hierarchical relations
                   The ontology should have at least an object property defined
                   * No omission of subclass partition                                             N OSP = SP D/CSC
                   SP D: Number of subclass-partitions defined on classes with the corresponding disjoint constraint
                   CSC: Number of classes with a set of direct subclasses identified
                   The ontology should have at least a class hierarchy, without considering the root class (Thing)
                   * No omission of exhaustive subclass partition                                 N OESP = CCA/CDSC
                   CCA: Number of classes with a set of disjoint direct subclasses and a covering axiom
                   CDSC: Number of classes with a set of disjoint direct subclasses identified
                   The ontology should have at least a class hierarchy, with a set of disjoint direct subclasses
                   Coverage of classes [12]                                               Coverage(Oc ; Fc ) =| Oc ∩ Fc | / | Fc |
                   Oc : Set of classes in the ontology
                   Fc : Set of classes in a frame of reference
                   The frame of reference should have at least a class
                   Coverage of relations between classes [12]                     Coverage(Orc ; Frc ) =| Orc ∩ Frc | / | Frc |
                   Orc : Set of relations between classes in the ontology
                   Frc : Set of relations between classes in a frame of reference
                   The frame of reference should have at least a relation between classes
                   Coverage of relations between instances [12]                   Coverage(Ori ; Fri ) =| Ori ∩ Fri | / | Fri |
                   Ori : Set of relations between instances in the ontology
                   Fri : Set of relations between instances in a frame of reference
                   The frame of reference should have at least a relation between instances
                   Coverage of instances [12]                                              Coverage(Oi ; Fi ) =| Oi ∩ Fi | / | Fi |
                   Oi : Set of instances in the ontology
                   Fi : Set of instances in a frame of reference
                   The frame of reference should have at least an instance
                   Coverage of entity features [15]                           Coverage(Of c ; Ff c ) =| Of c ∩ Ff c | / | Ff c |
                   Of c : Set of entity features in the ontology
                   Ff c : Set of entity features in a frame of reference
                   The frame of reference should have at least an entity feature
                   Coverage of dimensions [15]                               Coverage(Odf c ; Fdf c ) =| Odf c ∩ Fdf c | / | Fdf c |
                   Odf c : Set of dimensions used to specify entity contextual features in the ontology
                   Fdf c : Set of dimensions used to specify entity contextual features in a frame of reference
                   The frame of reference should have at least a dimension used to specify entity contextual features
                   * The measure was redefined




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Redefinition and Statistical Analysis of Measures for Evaluating the Quality of Ontologies




                                                    Table 2. Conciseness measures
                   Measure
                   * Semantically different classes                                                  SDC = 1 − CSD/C
                   CSD: Number of classes with the same formal definition as other class in the ontology
                   C: Number of classes in the ontology, without considering the root class (Thing)
                   The ontology should have at least a class hierarchy, without considering the root class (Thing)
                   * Semantically different instances                                               SDI = 1 − ISD/I
                   ISD: Number of instances with the same formal definition as other instance in the ontology
                   I: Number of instances in the ontology
                   The ontology should have at least an instance
                   * Nonredundant subclass-of relations                                         N RSR = 1 − RSCR/HR
                   RSCR: Number of redundant subclass-of relations in the ontology
                   HR: Number of hierarchical relations
                   The ontology should have at least a hierarchical relation, without considering the root class (Thing)
                   * Other nonredundant relations                                        ON RR = 1 − RN HR/N HR
                   RN HR: Number of redundant non-hierarchical relations in the ontology
                   N HR: Number of non-hierarchical relations
                   The ontology should have at least a non-hierarchical relation
                   * Nonredundant instance-of relations                                              N RIR = 1 − RIOR/IOR
                   RIOR: Number of redundant instance-of relations in the ontology
                   IOR: Number of instance-of relations in the ontology
                   The ontology should have at least an instance-of relation
                   Precision of classes [12]                                       P recision(Oc ; Fc ) =| Oc ∩ Fc | / | Oc |
                   Oc : Set of classes in the ontology
                   Fc : Set of classes in a frame of reference
                   The ontology should have at least a class, without considering the root class (Thing)
                   Precision of relations between classes [12]                    P recision(Orc ; Frc ) =| Orc ∩ Frc | / | Orc |
                   Orc : Set of relations between classes in the ontology
                   Frc : Set of relations between classes in a frame of reference
                   The ontology should have at least a relation between classes
                   Precision of entity features [12]                              Coverage(Of c ; Ff c ) =| Of c ∩ Ff c | / | Of c |
                   Of c : Set of entity features in the ontology
                   Ff c : Set of entity features in a frame of reference
                   The ontology should have at least an entity feature
                   Precision of instances [12]                                          P recision(Oi ; Fi ) =| Oi ∩ Fi | / | Oi |
                   Oi : Set of instances in the ontology
                   Fi : Set of instances in a frame of reference
                   The ontology should have at least an instance
                   * The measure was redefined




                                              Table 3. Syntactic correctness measures
                                     Measure
                                     Lawfulness [5]                                            SL = Xb/N S
                                     Xb: Total breached syntactical rules
                                     N S: Number of statements in the ontology
                                     The ontology should have at least a statement
                                     Richness [5]                                              R = Z/Y
                                     Z: Number of syntactic features used in the ontology
                                     Y : Number of syntactic features available in the ontology language
                                     The ontology language should have at least a syntactic feature




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                                            Table 4. Semantic correctness measures
                   Measure
                   Interpretability [5]                                                                   IN = SW/W CP
                   SW : Number of words used to define classes and properties that have at least a sense listed in WordNet
                   W CP : Number of different words used to define classes and properties in the ontology
                   The ontology should have at least a class or property name
                                                                                                                   P
                   * Clarity                                                                              CL = T N/ i Si
                   T N : Total of class or property names in the ontology that have at least a sense listed in WordNet
                   Si : Number of word senses for Ni in WordNet, where Ni is the name of the class or property i
                   The ontology should have at least a class or property name that has at least a sense listed in WordNet
                   * Non-circularity errors at distance 0                                 N CE0 = 1 − Cycles(O; 0)/HR
                   Cycles(O; 0): Number of cycles detected between a class with itself
                   HR: Number of hierarchical relations, without considering the root class (Thing)
                   The ontology should have at least a hierarchical relation, without considering the root class (Thing)
                   * Non-circularity errors at distance 1                                 N CE1 = 1 − Cycles(O; 1)/HR
                   Cycles(O; 1): Number of cycles detected between a class and an adjacent class
                   HR: Number of hierarchical relations, without considering the root class (Thing)
                   The ontology should have at least a hierarchical relation, without considering the root class (Thing)
                   * Non-circularity errors at distance d                                 N CEd = 1 − Cycles(O; d)/HR
                   Cycles(O; d): Number of cycles detected between a class and another at d classes away
                   HR: Number of hierarchical relations, without considering the root class (Thing)
                   The ontology should have at least a hierarchical relation, without considering the root class (Thing)
                   * Subclass partition without common instances                               SP N CI = 1 − SP CI/I
                   SP CI: Number of instances that belong to more than one subclass of a partition in the ontology
                   I: Number of instances in the ontology
                   The ontology should have at least an instance
                   * Subclass partition without common classes                                  SP N CC = 1 − SP CC/C
                   SP CC: Number of classes belonging to more than one subclass of a partition in the ontology
                   C: Number of classes in the ontology, without considering the root class (Thing)
                   The ontology should have at least a class, without considering the root class (Thing)
                   * Exhaustive subclass partition without common instances             ESP N CI = 1 − ESP CI/I
                   ESP CI: Number of instances belonging to more than one subclass of an exhaustive partition in the
                   ontology
                   I: Number of instances in the ontology
                   The ontology should have at least an instance
                   * Exhaustive subclass partition without common classes                   ESP N CC = 1 − ESP CC/C
                   ESP CC: Number of classes belonging to more than one subclass of an exhaustive partition in the
                   ontology
                   C: Number of classes in the ontology, without considering the root class (Thing)
                   The ontology should have at least a class, without considering the root class (Thing)
                   * Exhaustive subclass partition without external instances                ESP N EI = 1 − ESP EI/I
                   ESP EI: Number of instances of a base class that do not belong to any class of the exhaustive subclass
                   partition of the base class
                   I: Number of instances in the ontology
                   The ontology should have at least an instance
                   * The measure was redefined




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Redefinition and Statistical Analysis of Measures for Evaluating the Quality of Ontologies




                                              Table 5. Representation correctness measures
                      Measure
                                                                                                                            P
                      Principle of entities [15]                                                                     PE =         k
                                                                                                                                        αk /E
                      E: number of entities
                      The ontology should have at least an entity
                                                                                                                            P
                      Principle of intended use of entities [15]                                                     PU =           k
                                                                                                                                        αk /U
                      U : number of intended uses for all entities
                      The ontology should have at least an intended use for an entity
                                                                                                                          P
                      Principle of entity relations [15]                                                           PR =       k
                                                                                                                                  αk /RE
                      RE: number of relations identified for all entities
                      The ontology should have at least a relation between entities
                                                                                                                            P
                      Principle of simple entity features [15]                                                   P CS =       k
                                                                                                                                    αk /CS
                      CS: number of simple entity features identified for all entities
                      The ontology should have at least a simple entity feature
                                                                                                                          P
                      Principle of simple, measurable entity features [15]                                     P CM =       k
                                                                                                                                αk /CM
                      CM : number of simple, measurable entity features identified for all entities
                      The ontology should have at least a simple, measurable entity feature
                                                                                                                          P
                      Principle of complex entity features [15]                                                  P CC =       k
                                                                                                                                  αk /CC
                      CC: number of complex entity features identified for all entities
                      The ontology should have at least a complex entity feature
                                                                                                                            P
                      Principle of common entity features [15]                                                     P Cc =       k
                                                                                                                                    αk /Cc
                      Cc: number of common entity features identified for all entities
                      The ontology should have at least a common entity feature
                      αk = 0 if the k element is not represented; αk = 0.5 if the k element is represented in an incomplete
                      form; and αk = 1 if the k element is well represented




                  4.1       Evaluation of Measures


                  A statistical treatment of the data was performed in order to highlight the
                  most important quality characteristics of ontologies and synthesize them by a
                  few parameters. A total of 39 measures were calculated semi-automatically to
                  a set of 8 ontologies. InfoStat, Student Version3 , was used to do the statistical
                  analysis of this set of measures. Mean lets see the behavior of each measure on
                  the set of ontologies; position measures, the dispersion of data (deviation; Q1,
                  first quartile; and Q3, third quartile).


                  Table 6. Statistical of completeness measures                Table 7. Statistical of conciseness measures
                  Variable              n Mean S.D. Min Max Q1 Median Q3       Variable             n Mean S.D. Min Max Q1 Median Q3
                  NSC                   6 0,17 0,41 0,00 1,00 0,00 0,00 0,00   SDC                  6 0,75 0,28 0,39 1,00 0,53 0,78 1,00
                  EUR                   8 0,15 0,35 0,00 1,00 0,00 0,00 0,00   SDI                  4 1,00 0,00 1,00 1,00 1,00 1,00 1,00
                  DRR                   8 0,63 0,41 0,00 1,00 0,00 0,82 0,87   NRSR                 6 1,00 0,00 1,00 1,00 1,00 1,00 1,00
                  NOSP                  6 0,09 0,13 0,00 0,30 0,00 0,03 0,19   ONRR                 7 0,86 0,38 0,00 1,00 1,00 1,00 1,00
                  NOESP                 3 0,50 0,50 0,00 1,00      0,50        NRIR                 4 1,00 0,00 1,00 1,00 1,00 1,00 1,00
                  Coverage(Oc;Fc)       8 0,22 0,07 0,16 0,36 0,16 0,20 0,24   Precision(Oc;Fc)     8 0,33 0,20 0,07 0,57 0,08 0,31 0,50
                  Coverage(Orc;Frc)     8 0,36 0,23 0,10 0,70 0,10 0,35 0,50   Precision(Orc;Frc)   8 0,16 0,16 0,02 0,38 0,03 0,07 0,33
                  Coverage(Ofc;Ffc)     8 0,02 0,03 0,00 0,07 0,00 0,01 0,04   Precision(Ofc;Ffc)   8 0,00 0,00 0,00 0,00 0,00 0,00 0,00
                  Coverage(Odfc;Fdfc)   8 0,93 0,15 0,58 1,00 0,90 1,00 1,00   Precision(Oi;Fi)     4 0,00 0,00 0,00 0,00 0,00 0,00 0,00



                  3
                       http://www.infostat.com.ar/




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                      Regarding completeness (Table 6), only two of the nine measures have a
                  mean greater than 0.6. The measure with the highest mean value is Coverage
                  of dimensions (Coverage(Odf c ; Fdf c )); 90.0% of ontologies have a value greater
                  than or equal to 0.9, meaning that most of the dimensions used to specify en-
                  tity contextual features were made explicit in the ontology. Then, Domains and
                  ranges of relations (DRR) follows with a mean of 0.63, which determines the
                  proportion of domain and range of the relations and functions exactly and pre-
                  cisely delimited. The frame of reference had no instances. Then, the measures
                  Coverage of relations between instances and Coverage of instances, not listed in
                  Table 6, could not be calculated.
                      In regards to conciseness (Table 7), except in Precision, all other measures
                  have high values. Half of ontologies have all of instances semantically different
                  and nonredundant instance-of relations (SDI and N RIR are optimal). The other
                  half has no instances. No ontologies with hierarchical relations have redundant
                  subclass-of relations (N RSR has optimum value in all measures). Semantically
                  different classes (SDC) has a mean of 0.75 and 75% of ontologies have a value
                  greater than or equal to 0.53, meaning that more than half of subclasses are
                  defined with different characteristics. 75% of ontologies do not have redundant
                  non-hierarchical relations (ON RR is optimal).


                  Table 8. Statistical of semantic correctness Table 9. Statistical of syntactic correctness
                  measures                                          measures
                  Variable n Mean S.D. Min Max Q1 Median Q3         Variable n Mean S.D. Min Max Q1 Median Q3
                  IN       8 0,52 0,28 0,21 0,96 0,31 0,43 0,50     SL       8 1,00 0,00 1,00 1,00 1,00 1,00 1,00
                  CL       8 0,34 0,14 0,13 0,52 0,15 0,40 0,40     R        8 0,05 0,03 0,01 0,11 0,03 0,03 0,05
                  NCE0     6 1,00 0,00 1,00 1,00 1,00 1,00 1,00
                  NCE1     6 1,00 0,00 1,00 1,00 1,00 1,00 1,00     Table 10. Statistical of representation correct-
                  NCEd     6 1,00 0,00 1,00 1,00 1,00 1,00 1,00     ness measures
                  SPNCI    4 0,75 0,50 0,00 1,00 0,00 1,00 1,00      Variable n Mean S.D. Min Max Q1 Median Q3
                  SPNCC    8 0,96 0,06 0,88 1,00 0,88 1,00 1,00      PE       8 0,10 0,04 0,06 0,17 0,06 0,11 0,13
                  ESPNCI   4 1,00 0,00 1,00 1,00 1,00 1,00 1,00      PU       8 0,90 0,09 0,80 1,00 0,83 0,88 1,00
                  ESPNCC 8 1,00 0,00 1,00 1,00 1,00 1,00 1,00        PR       8 0,36 0,23 0,10 0,70 0,10 0,35 0,50
                  ESPNEI   4 1,00 0,00 1,00 1,00 1,00 1,00 1,00      PCS      4 0,90 0,13 0,75 1,00 0,75 0,92 1,00
                                                                     PCM      4 0,63 0,48 0,00 1,00 0,00 0,75 1,00




                      In relation to the semantic correctness (Table 8), the measures are mostly
                  high. The hierarchies are well defined, without cycles (N CE0, N CE1, and
                  N CED), as well as the exhaustive subclass partitions (ESP N CI, ESP N CC,
                  and ESP N EI). By contrast, ontologies are moderately interpretable and un-
                  clear; 75% of them have a value less than or equal to 0.5 and 0.4, respectively.
                      As for syntactic correctness (Table 9), it can be observed that the ontologies
                  are syntactically correct, but the proportion of syntactic features used is very
                  low, despite the development of ontologies supported by a case tool.
                      Finally, as to the representation correctness (Table 10), on average, 90%
                  of the intended use and simple features of entities is represented according to
                  its principle. However, only in 10% of cases, on average, the representation of
                  entities is performed through classes of ontology. The measures Principle of




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Redefinition and Statistical Analysis of Measures for Evaluating the Quality of Ontologies




                  complex entity features and Principle of common entity features could not be
                  calculated because the ontologies do not have these characteristics.


                  5    Discussion and Conclusions

                  In this paper, the reformulation of some measures of the OntoQualitas framework
                  has been presented, and the results of a preliminary analysis over the values
                  obtained from applying such measures to a set of ontologies have been shown.
                      According to the results, the evaluated ontologies do not fulfill adequately the
                  second requirement, i.e., the representation of the information strictly necessary
                  for the interchange. In part, this may be due to the ontology learning tool used to
                  generate the base ontologies that do not add necessary and sufficient conditions,
                  or existential and universal restrictions, among others.
                      Looking at the syntactic correctness measures, it can be observed that the
                  richness of language was not seized, despite the use of case tools for the develop-
                  ment of ontologies. The use of ontology learning techniques contributed to this,
                  as only limited to map the elements of the source into the ontology language
                  elements, untapped all syntactic features available.
                      As for the semantic interpretation, measures revealed that the names for the
                  ontology elements (classes, relations, properties) were not properly selected.
                      Regarding the representation correctness, an unexpected result is the low
                  representation of entities through the ontology classes.
                      Finally, these measures allow detecting errors in the development of ontolo-
                  gies, which affects its quality. An exploratory analysis of the data allowed to
                  characterize the studied ontologies. Future work is to carry out an inferential
                  statistical analysis to a larger set of ontologies that allows analyzing the possible
                  interdependence between measures, define acceptance thresholds of measures,
                  and propose a strategy for assessing the quality of ontologies.


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