Semantic technologies for open interaction systems

Abstract

Open interaction systems play a crucial role in agreement technologies because they are software devised for enabling autonomous agents (software or human) to interact, negotiate, collaborate, and coordinate their activities in order to establish agreements and manage their execution. Following the approach proposed by the recent literature on agent environments those open distributed systems can be efficiently and effectively modeled as a set of correlated physical and institutional spaces of interaction where objects and agents are situated. In our view in distributed open systems, spaces are fundamental for modeling the fact that events, actions, and social concepts (like norms and institutional objects) should be perceivable only by the agents situated in the spaces where they happen or where they are situated. Institutional spaces are also crucial for their active functional role of keeping track of the state of the interaction, and for monitoring and enforcing norms. Given that in an open distributed and dynamic system it is fundamental to be able to create and destroy spaces of interaction at run-time, in this paper we propose to create them using Artificial Institutions (AIs) specified at design time. This dynamic creation is a complex task that deserves to be studied in all details. For doing that, in this paper, we will first define the various components of AIs and spaces using Semantic Web Technologies, then we will describe the mechanisms for using AIs specification for realizing spaces of interaction. We will exemplify this process by formalizing the components of the auction Artificial Institution and of the spaces created for running concrete auctions.

Appendix A: OWL 2 DL

OWL 2 DL is a practical realization of a Description Logic known as $\mathcal SROIQ(D)$. It allows one to define classes, properties, and individuals. An OWL ontology consists of: a set of class axioms that specify logical relationships between classes, which constitutes the Terminological Box (TBox); a set of property axioms to specify logical relationships between properties, which constitutes a Role Box (RBox); and a collection of assertions that describe individuals, which constitutes an Assertion Box (ABox). Classes are formal descriptions of sets of objects (taken from a nonempty universe), and individuals can be regarded as names of objects of the universe. A class is either a basic class (i.e., an atomic class name) or a complex class build through a number of available constructors. Properties can be either object properties, which represent binary relations between objects of the universe, or data properties, which represent binary relationships between objects and data values (taken from XML Schema datatypes).

Through class axioms one may specify that subclass ($\sqsubseteq$) or equivalence ($\equiv$) relationships hold between certain classes, and that certain classes are disjoint. In particular, class axioms allow one to specify the domain and range of a property p (p: A $\rightarrow$ B where class A is the domain and class B is the range), and that a property is functional or inverse functional. Property axioms allow one to specify that a given property (or chain of subproperties) is a subproperty of another property, that two properties are equivalent, or that a property is reflexive, irreflexive, symmetric, asymmetric, or transitive. Finally, assertions allow one to specify that an individual a belongs to a class C: C(a), that an individual a is (or is not) related to another individual b through an object property R: R(a,b), that an individual is (or is not) related to a data value through a data property, or that two individuals are equal or different.

Complex classes can be specified by using Boolean operations on classes: C $\sqcup$ D is the union of classes, C $\sqcap$ D is the intersection of classes, and $\lnot$ C is the complement of class C. Classes can be specified also through property restrictions: (i) $\exists$ R.C denotes the set of all objects that are related through property R to some objects belonging to class C, at least one; if we want to specify to how many objects an object is related we should write: $\le$ nR, $\ge$ nR, =nR where n is any natural number; (ii) $\forall$ R.C denotes the set of all objects that are related through R only to objects belonging to class C; (iii) R $\ni$ a denotes the set of all objects that are related to a through R.