A Model of Roles in Ontology Development Tool: Hozo

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A Model of Rolesin Ontology Development Tool
Hozo

• Sunagawa, E., Kozaki, K., Kitamura, Y.,
  Mizoguchi, R.
• I.S.I.R., Osaka University, Japan

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Back ground

• The world is full of roles.
• Wife, father, teacher, speaker, food, symptom,
  conclusion, product, doer(actor), input, output,
  etc.
• Roles are different from so-called natural
  types(referred to as basic concepts) in the way
  of losing its identity.
• While basic concepts such as human cannot lose
  its identity without dying(disappearing from the
  real world), roles can. For example, a teacher
  can stop being a teacher without dying
• There remain some unsolved problems
• Counting problem(number of guests vs. number of
  persons)
• Universal vs. Particular problem
• How many kinds of roles exist?
• How can we manage individuals(instances) related
  to roles?
• We dont have a sophisticated model of role nor a
  tool for dealing with roles appropriately.

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Professor is-a Human?
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Agenda

• Enumerate characteristics of role
• Issues to solve
• Our model of role
• Role model in our research
• Instances of roles
• Types of roles
• Primitive and compound roles
• Role representation in Hozo
• Two ways
• Implicit organization(Current)
• Explicit hierarchical organization(New)
• OWL translation
• Concluding remarks

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Characteristics of roles

• Roles are anti-rigid GuarinoA role is a
  property that is contingent(non-essential) for
  all its instances.
• Roles are dynamic MassaloAn entity can
  start/stop to play a role and a role can be
  played by multiple players.
• Roles are (externally) founded GuarinoRoles
  necessarily need some external concepts to define
  them.
• Roles are dependent on the context in which they
  are definedTeacher role depends on a school,
  medical doctor and nurse roles on a hospital,
  husband/wife on a marital relation, etc. They are
  specified according to their way of participation
  in the context.
• An entity can play multiple roles at the same
  timeA man can be a husband, a professor and dean
  at the same time.

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Characteristics of roles(contd)

• An entity can play the same role type many
  timesA person can become a student more than
  once. Those instances of student role are
  different from each other.
• A role can play another role
• A role is played by multiple entities at the same
  time It is true for drama roles such as Hamlet.
  How about Citizen role?
• Some features of an entity playing a role can be
  role-specific.In the bicycle case, the attribute
  of maximum length of riding time could be
  associated with the person who is playing the
  Rider role. And, the attribute is useless when
  he/she does not ride a bicycle.
• A teacher is a teacher while sleeping Loebe 2005
  .It is OK for teacher role.A pedestrian is not
  a pedestrian while sleeping.It is the matter of
  the way of participation in a context in which
  the role is define.

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Issues of roles

• Counting problemThe number of passengers in one
  week may be greater than the number of individual
  persons traveling with that means during the same
  period Wilinga 95.
• Universal vs. Individual Loebe 05Instance of a
  role?Its instantiation is done by being played
  by an entity (an individual)?Is an instance of
  role can exist without being played by any
  others? Teacher or Husband
• Sophisticated instance managementNot discussed
  extensively to date. It clearly specifies how a
  role is special
• Enumeration of role typesTop-level categories of
  roles Loebe 05,
• Primitive vs. Compound rolesHusband is
  primitive.Teacher is dependent on school and
  teaching action contexts.

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Our understanding of role

• Role
• An entity which is played by another entity in a
  context.
• What is recognized depending on the way of
  participation of an entity in a context
• We have been focusing on the context dependency
  of rolesas their essential attributes (rather
  than player link) .
• Mizoguchi 2000, Kozaki 2002
• Context Dependency corresponds roughly to
  foundation of roles and role-of.
• Guarino 1992Masolo 2004Loebe 2005
• Basic concept(natural type)
• Corresponding to firstness by Sowa
• Target roles of the research
• Teacher, Presenter, Audience, Minister, Patient,
  Actor, Fuel, Food, Symptom, Input, Output,
  Product

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Important distinctions

• Class level (Universal)
• Role Concept, Potential player, Role-Holder
• Role Concept
• A concept which is played by something
• Potential Player (Role-Playable Thing)
• A thing which is able to play a role
• Role-Holder (abstraction of Role-Playing Thing)
• A thing which is playing a role
• Both Role concept and Role holder are class-level
  things and have their own instance-level things
• By play, we mean act as, that is, it
  contingently acts as the role

In a Context, a Player plays a Role (Role
Concept), and then, becomes a Role-Holder.
a School
a Person
a Teacher Role
a Teacher
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More about a Potential player, a Role Concept and
a Role-Holder

• Instance levelExample In Osaka High School,
  there is a vacancy on a Teacher position. John
  fills it, and then he becomes a Teacher of the
  school.
• A vacancy on the Teacher-1 arises when the
  Teacher role-1 is not played.
• A vacancy is conceptualized as an instance of a
  role concept.
• If Osaka High School does not exist, the instance
  Teacher role-1 never exists.
• An instance of a role concept cannot exist
  independently of an instance of its context.
• Teacher role has two states
• An instance of a role concept has two
  statesplayed and not played.

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Conceptual Framework of Role
Role-holder
Context
Teacher
School
Role concept
Potential player
TeacherRole
Person
depend on
playable
Height
Subject
Name
Age
Weight
Class
Group A
Group B
Group C
Role concept and role holder and the identity
definition of role holder, IDRole holderf
(IDRoleConcept, IDPlayer).
The individual corresponding to Teacher is the
composite of these two instances and totally
dependent on them
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More about a Player, a Role Concept and a
Role-Holder (contd)

• Example John is no longer recognized as a
  Teacher, when
• the position of the Teacher-1 which John filled
  disappears
• John quits the Teacher
• John dies
• A Role-Holder disappears in the cases(1) an
  instance of a Role concept disappears(2) an
  instance of a Player stops playing the role(3)
  an instance of a Player disappears

Teacher-1
context
Role-Holder
Osaka High School
TeacherRole-1
John
playing
Role Concept
depend on
Player
(3)
(1)
(2)
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Implications

• Role ? role concept and role holderRole
  concept at the class level Role Role concept
  at the instance level ? Instance of Role Role
  concept can be instantiated without being played.
• Hamlet role exists independently of it is being
  played or not
• My professor role does as well
• While the term Role is the target of the
  research of roles, at the same time, it has been
  the source of confusion, since it hides the
  difference between role concept and role
  holder.
• Play link has two semantics
• Potential player/playable(class level)
• Playing(instance level)

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Context-Dependency of a Role Concept

• Context Dependency
• Role concepts are recognized dependently on a
  context.
• Based on the dependency, we can uncover the
  following three characteristics of
• Instances of a role concept and a role-holder
• Categories of role concept
• Two kinds of role concepts a primitive and a
  compound role concept

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Top-level Categories of Role Concepts

• Role Concepts are characterized by the Context
  they belong to
• In order to classify them according to categories
  of contexts, we can utilize their foundation.
• e.g.
• Task Role
• Symptom Role (Fault Diagnosis)
• Conclusion Role (Reasoning)
• Functional role
• Steering wheel role (Steering Function)
• Level control valve role played by a flow
  control valve (Function)
• Action-related role
• Actor role (Any action)
• Teaching agent role (Teaching action)
• Target object role (Action object)

Top-level classification of concepts which can be
contexts

• Organizational Role
• Employee
• Manager (Compound)
• Process-related role
• Product role (Final output)
• Residue role (How it is processed)
• Relational role
• Friend role (Friendship)
• Parent role (Parent-Child Relation)

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Primitive and CompoundRole Concepts

• Example. 1
• Teacher is recognized not only as a staff member
  of a school but also as a person who teaches
  students.
• Teacher role is a composite of Staff role and
  Teaching agent role.
• Example. 2
• Only a Japanese citizen can be Japanese prime
  minister.
• Japanese prime minister role can be played by
  Japanese citizen who is played by a human.
• Such a Role needs to be played together with
  other roles.

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Primitive and CompoundRole Concepts (contd)

• In some case, a player stops playing one of the
  roles, and then, some of others will
  automatically be un-played.
• Requirement Masolo04, Roles can play Roles.
  Steimann00
• Role-Holders can play Roles (in our terms).
• Such a role concept depends on multiple contexts.
• e.g., Peer tutoring context in Group learning
• A learner is expected to play Peer tutor role
  to learn by Learning by Teaching strategy. Peer
  tutor role depends on both of Learning context
  and Teaching action context.
• Two Kinds of Roles according to the complexity of
  their context-dependencies
• Primitive Roles
• have Single-context dependency
• e.g.) Wife/Husband, Speaker, Invitee, Learner,
  Citizen, etc.
• Compound Roles
• have Multiple-context dependency
• e.g.) Invited Speaker, Peer tutor in Learning by
  Teaching, Japanese Primary Minister, etc.

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Compound Roles
Role-holders can play roles.(an example of that
only a Japanese citizen can be Japanese prime
minister.)
J. prime minister
context
Role-Holder
Japanese ministry
J. prime minister role
Japanese citizen
playable
Role Concept
Potential player
depend on
Japanese citizen
context
Role-Holder
Japanese political system
Japanese citizen role
Human
playable
Role Concept
depend on
Potential player
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Organizing Role Concepts

• A quick view

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Implementation of Our Framework Hozo

• Hozo an environment for building/using
  ontologies
• has supported role representation since 1999
• Kozaki et al. 2002 Hozo An Environment for
  Building/Using Ontologies Based on a Fundamental
  Consideration of Role and Relationship. In
  Proceedings of EKAW2002
• Supporting ontology development based on
  discrimination of role concepts from basic
  concepts
• It will help developers of ontology
• To represent relations between roles
• To grasp a whole image of roles in a target world

http//www.hozo.jp (mail info_at_hozo.jp)
A Hierarchy of Basic Concepts(context and
players)
A Hierarchy ofRole Concepts
(under development)
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Organizing Role Concepts of Upper Classes

• We can classify roles according to the
  categories of Contexts.
• The categories are utilized at the top level of
  classification in a hierarchy of role concepts.

a hierarchyofRole Concepts
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Organizing Role Concepts of Middle Classes

• Primitive Roles, which depend on a single
  context, are organized at middle level classes by
  three guidelines
• Organization according to the manners of
  participation of players in their contexts
• Organization according to is-a relations among
  their context
• Organization by definition of intermediate role
  concepts

a hierarchyofRole Concepts
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Organizing Role Concepts of Lower Classes

• Compound role concepts, which depend on multiple
  contexts, are organized at the lower level
  classes.
• To organize compound role concepts, we derive a
  framework called Role Aggregation.

Role-holders can play roles.
a hierarchyofRole Concepts
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Representation of Role Aggregation A

• e.g. Teacher Role is a composite of Staff Role
  and Teaching Agent Role.
• To define is-a and part-of relations among
  the compound roles and its component roles
• Teacher Role is defined by aggregating
• Staff Role inheritance through is-a relation
• Teaching Agent Role as a role-part

In the hierarchy of role concepts

• An is-a relation which we used in role
  aggregation correspond to requirement relation.
  
• Masolo 2004
• By Role Part, we mean a role concept defined as a
  part of a compound role.

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Representation of Role Aggregation B

• e.g. Teacher Role is a composite of Staff Role
  and Teaching Agent Role.
• A Staff is defined as a player of a Teacher Role

In the hierarchy of basic concepts
LEGEND
(specialize)
representation of a concept in a hierarchy of
basic concepts
(RH Role Holder)
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Scope of Our Framework

• Compound role
• Japanese Prime minister Role (Head Role
  Japanese Minister Role Japanese Citizen role)
• Teacher role (School Staff Teaching Agent)
• Attribute role
• Height role played by length
• State-related role
• The Sick role (Sickness)
• Beginner role (history)
• UFO (Unidentified Flying Object)
• Intransitive action-related role
• Walker, Runner
• Rotating object
• Abstract role
• School staff role (Super class role of School
  teacher and School clerk roles)

• Classification by Context
• Task role
• Symptom role (Fault Diagnosis)
• Conclusion role (Reasoning)
• Functional role
• Steering Wheel role (Steering Function)
• Level control valve played by a flow control
  valve (Function)
• Action-related role
• Actor role (Any action)
• Teaching Agent role (Teaching Action)
• Target object role (Action object)
• Process-related role
• Product role (Final output)
• Residue role (How it is processed)
• Organizational (Social) role
• Staff role
• Student role, Nurse role compound
• Relational role
• Friend role (Friendship)

Not covered yet
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OWL translation
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Several simple role models in OWL
(a) (b) (c)
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The full model in OWL
(d)
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Evaluation
Characteristics of Classes
Characteristics of Individuals
OK represented, - not represented, -/OK
represented partially
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Concluding Remarks

• Evaluation and discussion in terms of the
  characteristics
• How the issues raised are solved.

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Main Claims of our Framework

• Differentiation1 between Role concept (teacher
  role) and Role-holder (teacher)Differentiation2
  between the instantiation operation of the role
  concept and the playing operation.
• Semantics of playable/playing link is property
  inheritancerather than instantiation
• A Role-holder disappears when(1) an instance of
  a Role Concept disappears(2) an instance of a
  Player disappears (3) an instance of a Player
  stops playing the role
• Both Role concept and Role holder are class-level
  things and have instance-level things.
• Any Role concept has its identity. An instance
  corresponding to Role- holder is the composite of
  an instance of its Player and that of Role
  concept.
• Linked to Context

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Conceptual Framework of Role
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Evaluation and discussion

• Roles are anti-rigidGuarinoA potential player
  contingently plays a role concept only in a
  context.
• Roles are dynamicFrom the definition, the player
  easily stops/starts to play role concepts. A
  role concept can be played by multiple players
  one after another.
• Roles are externally foundedYes, role concepts
  are necessarily defined by referring to a part(s)
  or a participant(s) of a whole/relation as a
  context in our model.
• Roles are dependent on the context in which they
  are definedYes. See (3).
• An entity can play multiple roles at the same
  timeYes, there is no restriction in our model
  concerning the time about the event of playing
  role concepts.
• An entity can play the same role type many
  times.Yes, there is no restriction for this in
  our model. In the case of individual role,
  however, we need discussion. No person can play
  the same student role multiple times. the Hamlet
  role is OK.as an individual role multiple times.
  This difference comes not from the model of roles
  but from the ontological nature of the type of
  the role concept.

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Evaluation and discussion (Contd)

• A role is played by multiple entities at the same
  time.No restriction in our model. If any, a
  restriction comes from the ontology. Teacher
  role-1 of a school-1 cannot be played by multiple
  players at the same time theoretically. Neither
  for citizenship which has its own ID. OK for a
  drama role. Hamlet can be multiply played at the
  same time.
• A role can play another roleYes, a role holder
  can play another role concept
• Some features of an entity playing a role can be
  role-specific.Yes, as shown in Fig. 2, some
  properties coming from the role concept are
  shared with the role player as its own properties
  in our model.
• A teacher is a teacher while sleeping.Partly
  yes. Issue is the semantics about play relation
  or about the way of participation in the
  context. Teacher role and pedestrian role. In the
  case of process-related role, it is temporary. We
  need a rigorous definition of the semantics of
  play relation and/or the way of participation in
  the context, which will be revisited in the
  concluding remarks.

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Issues raised

• Counting problemRole concept and role holder and
  the identity definition of role holder, IDRole
  holderf (IDRole, IDPlayer).
• Universals vs. particulars 2.1 The statementA
  role is considered as a universal and whose
  instantiation is done by being played by an
  entity is not true. The key is the detachment of
  the instantiation operation of the role
  concept from the playing operation. 2.2 Whether
  role holder is a Universal or not and what is its
  instance? Role holder exists both in the
  universal(class) level and the particular(instance
  ) level. However, it cannot be directly
  instantiated. Role holder as a particular has to
  be made by composing individuals(particulars)
  of corresponding role concept and potential
  player. And, the role holder at the universal
  level is an abstraction of the individual made
  that way.
• Sophisticated instance managementThe semantics
  of part-whole relation. The key idea is that role
  concepts are attributed to parts of the context
  (whole/relation) which the parts belong to. A
  theory which explicitly explains the relations of
  parts and roles is necessary.
• Enumeration of role types
• Compound roles

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Future Work

• We plan to investigate
• Extension of our framework to be able to deal
  with a concept which depends on other kinds of
  concepts
• e.g.) UFO, The Sick, Rotating Object, Weapon
• several individuals can play the above, but it
  seems controversial to identify their contexts
• Instance management of Roles
• e.g.) A Teacher can stop playing a Teacher Role
  if he/she quits teaching. Can a Father stop
  playing a Father Role (biologically)?
• Inter-dependencies of components of Compound
  Roles
• In our framework, we can treat the dependency of
  a Compound Role to the essential component, but
  cannot yet the dependency among the components.

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Thank you!(and we will thank you much more if
you download Hozo fromhttp//www.hozo.jp )