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BEIJING UNIVERSITY OF POSTS AND

TELECOMMUNICATAIONS

2007-1-5

A Semantic Peer-to-Peer Overlay for Web Services Discovery

Shuang Kai

2007-1-5 2

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Agenda• Introduction• Thoughtway of our method• Semantic overlay node architecture• Routing Table & Neighborhood Table• Message Semantic Matching & Routing• Example• Experimental Evaluation• Conclusion

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Introduction-1

• service discovery mechanisms– centralized registry

• UDDI or DAML-S matchmaker– decentralized approach

• centralized registry– single point failure– performance bottleneck

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Introduction-2

• based on P2P technology– unstructured P2P network

• limitation on the scalability– structured P2P networks based on DHT

• logn routing hops – network of size n nodes• exact match

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Agenda

• Introduction• Thoughtway of our method• Semantic overlay node architecture• Routing Table & Neighborhood Table• Message Semantic Matching & Routing• Example• Experimental Evaluation• Conclusion

2007-1-5 6

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Thoughtway of our method

• structured P2P semantic method• different matching degree• extends the Plaxton mesh

– dynamic semantic overlay network– keyword prefix routing to semantic prefix

routing

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Characteristic Vector - 1

• semantic service description– OWL-S or WSMO

• characteristic vector– a series of numeric string– extract service’s information

• input, output, Pre-conditions and Effects• ontological concept

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Characteristic Vector - 2

service description: Advertisement1 = {C7, C6, C5, C4}

CV={10, 11, 0000, 0100}.

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Agenda

• Introduction• Thoughtway of our method• Semantic overlay node architecture• Routing Table & Neighborhood Table• Message Semantic Matching & Routing• Example• Experimental Evaluation• Conclusion

2007-1-5 10

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Semantic overlay node architecture -1

Knowledge BaseMatchmaker

Neighborhood Table

Execution and Communication module …

Registry Peer 1

Registry Peer 2

ServicePublish

Service Query

RouterTable

Query Processor

ServiceStore

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Semantic overlay node architecture -2

Knowledge BaseMatchmaker

Neighborhood Table

Execution and Communication module …

Registry Peer 1

Registry Peer 2

ServicePublish

Service Query

RouterTable

Query Processor

ServiceStore

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Agenda

• Introduction• Thoughtway of our method• Semantic overlay node architecture• Routing Table & Neighborhood Table• Message Semantic Matching & Routing• Example• Experimental Evaluation• Conclusion

2007-1-5 13

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Routing Table

• multiple rows• each rows holds a number of entries• semantic matching of the prefix up to an

element in the CV

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Neighborhood Table

• Contains the nodeID and IP address of the peers

• Set of peers that are closest to the local peer– Based on semantic similarity

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Agenda

• Introduction• Thoughtway of our method• Semantic overlay node architecture• Routing Table & Neighborhood Table• Message Semantic Matching & Routing• Example• Experimental Evaluation• Conclusion

2007-1-5 16

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Semantic Matching Degree

• Exact– If advertisement S and request Q are equivalent– S ≡ Q

• PlugIn– If S could always be used for Q– S is a plug-in match for Q, Q⊆S.

• Subsume– If S is more general than Q– S is a Subsume match for Q, S⊆Q

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Message Routing and Locating

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Agenda

• Introduction• Thoughtway of our method• Semantic overlay node architecture• Routing Table & Neighborhood Table• Message Semantic Matching & Routing• Example• Experimental Evaluation• Conclusion

2007-1-5 19

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Example

C3C7CAC0

C1C1C1C1C1C1C1C1

C1C1C1C1

C3C7CAC2

C3C7CBC2 C3C7C5C1

C3CBC9C6

C6C3C0CC

C1C1C1C1

C1C1C1C1

C1C1C1C1

Message ID

C3C7CAC0

Exact

Subsume

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Agenda

• Introduction• Thoughtway of our method• Semantic overlay node architecture• Routing Table & Neighborhood Table• Message Semantic Matching & Routing• Example• Experimental Evaluation• Conclusion

2007-1-5 21

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Experimental Evaluation - 1

1000 10000 1000001.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0 Pastry the Semantic Overlay

Ave

rage

num

ber o

f hop

s

Numbers of nodes

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Experimental Evaluation - 2

0 1 2 3 4 5 60.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Pro

babi

lity

Number of Hops

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Agenda

• Introduction• Thoughtway of our method• Semantic overlay node architecture• Routing Table & Neighborhood Table• Message Semantic Matching & Routing• Example• Experimental Evaluation• Conclusion

2007-1-5 24

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Conclusion

• Our System– support semantic matching

• ontological concept encoding scheme– based on the structured overlay network

• dynamic Plaxton mesh-like network

• Future work– improve the usability of this system

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Thank you！