1. Peer services: from Description to Invocation Manuel Oriol International Workshop on Agents and Peer-to-Peer Computing (AP2PC 2002)

2. Manuel Oriol - AP2PC 2002 2 Introduction P2P networks may be characterised by the fact that they are: Decentralised. Potentially Large. Very Dynamic. Heterogeneous. Provides (Distributed) Services.

3. Manuel Oriol - AP2PC 2002 3 Focus We want to ease the use of services from peer to peer: Adding services seamlessly. Deciding to invoke the most adapted service on demand. Using a mechanism adapted to the high dynamicity of P2P networks. Contribution An infrastructure for peer services that relies on...

4. Manuel Oriol - AP2PC 2002 4 Principles Associative Naming: Peers are not named at all but they specify what do the services they provide. Peers do not call methods on other peers, they specify what they want. Late Binding A request is served and bound on demand. Asynchronous Communications All communications are asynchronous and peers do not block.

5. Manuel Oriol - AP2PC 2002 5 Peer & Peer Services

6. Manuel Oriol - AP2PC 2002 6 Model

7. Manuel Oriol - AP2PC 2002 7 Invocation & Answer

8. Manuel Oriol - AP2PC 2002 8 How to Specify? Functionality: What does it do? (comparable to a method name) Behaviour How does it do it? (comparable to method signature) QoS How well does it do it? (comparable to the description of a method in an API)

9. Manuel Oriol - AP2PC 2002 9 Example of Code: Service providers Service BubbleSort(F: "sort": "BubbleSort", B: argument: (int a[]: return: int[], char a[] : return: char []), QoS: local)[2,5,2]{...} Service QuickSort(F: "sort": ”QuickSort", B: argument: int a[]: return: int[], QoS: local: “Complexity”: “Nlog(N)"), )[2,5,2]{...} Minimal Matching

10. Manuel Oriol - AP2PC 2002 10 Services Trees: BubbleSort F « Sort » « BubbleSort » ( B argument int []char [] return int []char [],,) QoS local

11. Manuel Oriol - AP2PC 2002 11 Services Trees: QuickSort (,,) F « Sort » « QuickSort » B argument int [] return int [] QoS local « Complexity » « Nlog(N) »

12. Manuel Oriol - AP2PC 2002 12 Example of code: Clients int a[]; T=Invoke((F: "sort", B: argument: a: return: int[], QoS: local: "Complexity": "Nlog(N)"), [2, 5, 2]); char a[]; T=Invoke((F: "sort”: “QuickSort”, B: argument: a: return: char[], QoS: local), [3, 5, 2]); Minimal Matching

13. Manuel Oriol - AP2PC 2002 13 Clients trees (1) F « Sort » ( B argument int [] return int [],,) QoS local « Complexity » « Nlog(N) » F « Sort » « BubbleSort » B argument int [] return int [] char [] return char [] QoS local F « Sort » « QuickSort » B argument int [] return int [] QoS local « Complexity » « Nlog(N) »

14. Manuel Oriol - AP2PC 2002 14 Client Trees (2) F « Sort » « QuickSort » ( B argument char [] return char [],,) QoS local « Complexity » « Nlog(N) » F « Sort » « BubbleSort » B argument int []char [] return int []char [] QoS local F « Sort » « QuickSort » B argument int [] return int [] QoS local « Complexity » « Nlog(N) »

15. Manuel Oriol - AP2PC 2002 15 Special Labels for Matching Ø: adds 1 to the depth of this branch. Ø*: the branch matches at an infinite depth. : the branch should terminate there (otherwise the depth is 0). ? : the label may be everything.

16. Manuel Oriol - AP2PC 2002 16 Relocalizing Peer Services in JXTA PeerGroup Services Basic With Service Manager

17. Manuel Oriol - AP2PC 2002 17 Conclusion We presented our architecture that addresses the problem of services in very dynamic environments through associative naming, late binding and asynchrony. We give a way of quantifying how well (possibly complex) descriptions match and prefer some services to others. We show that the principles may be adapted to decentralized P2P networks.

18. Manuel Oriol - AP2PC 2002 18 Future work We want to implement a prototype of this architecture on top of JXTA. We want to investigate further the use of already existing ontology technologies.

19. Manuel Oriol - AP2PC 2002 19 F « Sort » « QuickSort » B argument int [] return int [] QoS local « Complexity » « Nlog(N) »

20. Manuel Oriol - AP2PC 2002 20 F « Sort » « BubbleSort » B argument int [] return int [] char [] return char [] QoS local