a context based institutional normative environment
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A Context-based Institutional Normative Environment Henrique Lopes - PowerPoint PPT Presentation


  1. ������� – ������� – ������������������������������������������������������ ������������������������������������������������������ A Context-based Institutional Normative Environment Henrique Lopes Cardoso, Eugénio Oliveira LIACC, DEI / Faculdade de Engenharia, Universidade do Porto {hlc, eco}@fe.up.pt May 12 th 2008, COIN@AAMAS’08 ���������������������� ��������������� ������� � �

  2. ������� – ������� – ������������������������������������������������������ ������������������������������������������������������ COIN session: Norms violation and monitoring I “Formalising Situatedness and Adaptation in “A Context-Based Institutional Normative Electronic Institutions” Environment” � Situated � A common normative structure for several social systems � couple an EI with a previously existing environment (social system) � first the EI, then the specific “environments” ( contexts ) � Adaptability of the normative environment to each � Autonomic context � autonomous adaptation of the social system’s � agents exploit and adapt the normative rules to enhance performance environment to fit their purposes “A Hybrid Reputation Model Based on the Use of “A Context-Based Institutional Normative Organizations” Environment” � Organizational Norms (ON) vs. Individual Norms � “Specialization” of norms as an inheritance (IN) preventing mechanism � IN are specializations of ON � not necessarily more restricted in that sense � IN are more restricted than ON � (De)centralized hybrid reputation model � Norm monitoring model � collection of distributed evaluations � enables objective centralized reputation service � quality of reputation source ���������������������� ��������������� ������� � �

  3. ������� – ������� – ������������������������������������������������������ ������������������������������������������������������ Outline � Normative environment Top Context � Contexts and normative state N7 N1 N6 N2 N3 N5 Normative Framework N4 � Rules and semantics of deadline obligations Context B2 Context G1 � Norms, defeasible norm N1 N3 N5 N2 N8 N4 activations and hierarchical Context B1 normative framework N3 N5 N4’ � Example � Conclusions ���������������������� ��������������� �������

  4. ������� – ������� – ������������������������������������������������������ ������������������������������������������������������ Normative Environment � EI = Services + Normative Environment � Services � assist agents in contract establishment � contracts can be underspecified, relying on a normative framework � Normative Environment NE = � � � NS , IR , N � � � � � � Normative State NS � facts, obligations, fulfillments, violations, time � Institutional Rules IR � maintain the normative state by defining interrelations among its elements � Norms N � define the normative positions of each agent in the system ���������������������� ��������������� ������� ! !

  5. ������� – ������� – ������������������������������������������������������ ������������������������������������������������������ Contexts Context C = � � PC , CA , CI , CN � � � � � � � � C is an organizational structure � within which a set CA of agents � commits to a joint activity partially regulated by CN ⊆ ⊆ ⊆ ⊆ N � CI is a set of founding contextual info � PC is the parent context within which C is formed � Each Contract generates a Context Sub-context C’ = � � � PC’ , CA’ , CI’ , CN’ � � � � � � � C’ � � � C � � C’ is a sub-context of C = � � � � PC , CA , CI , CN � � � � if PC’ = C or PC’ � � C � � � C’ � � � � C � C’ � � � C or C’ = C � � Motivation: a B2B contractual agreement C forms a business-context for a more specific contract C’ ���������������������� ��������������� ������� " "

  6. ������� – ������� – ������������������������������������������������������ ������������������������������������������������������ Contexts (2) � Contextual info Info C ∈ ∈ ∈ CI ∈ � fully-grounded atomic formula in FOL � Motivation: a contract contains intrinsic information defining it (roles, exchanged values, provisions) � Normative State NS = { IRE 1 C1 , IRE 2 C2 , …, IRE n Cm ,} Cj is a fully-grounded atomic � each institutional reality element IRE i formula in FOL � ifact C (f, t) – institutional fact � time C (t) – time � obl C (a, f, t) – deadline obligation � fulf C (a, f, t) – fulfillment � viol C (a, f, t) – violation ���������������������� ��������������� ������� # #

  7. ������� – ������� – ������������������������������������������������������ ������������������������������������������������������ Institutional Rules Antecedent → → → → Consequent Rule R ::= ∧ ∧ ∧ ∧ ∧ ∧ ∧ ∧ IRE C IRE- C ¬ ¬ ¬ ¬ < ≤ < ≤ = = ≥ ≥ > > < < ≤ ≤ = = ≥ ≥ > > obl C (…) � Semantics of rules: substitution in FOL � substitution Θ Θ matches Antecedent with NS Θ Θ � apply Θ Θ to Consequent and add fully-grounded atomic formulae to NS Θ Θ � Use-case: implement the semantics of deadline obligations ���������������������� ��������������� ������� $ $

  8. ������� – ������� – ������������������������������������������������������ ������������������������������������������������������ Deadline Obligations � Deadline obligations in LTL (discrete time): obl C (a, f, t) ∧ (ifact C (f, t’) B time C (t)) � G fulf C (a, f, t) p B q : p before q obl C (a, f, t) ∧ (time C (t) B ifact C (f, t’)) � G viol C (a, f, t) G q : henceforth q obl C (a, f, t) ∧ (ifact C (f, t’) @ time C (t)) � G fulf C (a, f, t) ¬ (p B q) ∧ ¬ (q B p) p @ q : � Institutional Rules: obl C (a, f, t) ∧ ifact C (f, t’) ∧ ¬ time C (t) → fulf C (a, f, t) ifact B time obl C (a, f, t) ∧ time C (t) ∧ ¬ ifact C (f, t’) → viol C (a, f, t) time B ifact obl C (a, f, t) ∧ ifact C (f, t’) ∧ time C (t) → fulf C (a, f, t) ifact @ time X holds if (time B ifact) ! � fulfillment only if no violation: obl C (a, f, t) ∧ ifact C (f, t’) ∧ ¬ viol C (a, f, t) → fulf C (a, f, t) � Practical issues � need for rule evaluation after each NS update � relaxing this need: use IRE ’s time references � temporal deadlines ���������������������� ��������������� ������� % %

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