![](bg7.png)
identifiers, produce checksums, or calculate hashes
based on the metadata of the new document.
Delegating the orchestration of one those services
and the storage to those providers would actually
increase network usage: instead of invoking the first
service, receiving the id/checksum and sending all to
the StoreDoc, PDF and image files would have to go
to the first service and from there to the StoreDoc
provider. Therefore, instead of
T
final
= 2S
XML
+ 2S
ID
+ S
PDF
+ S
JPG
we would have
T
final
= 2S
XML
+ S
ID
+ 2S
PDF
+ 2S
JPG
which represents one less SID but one more SPDF
and SJPG. By using our proposed criterion, and
since the id/checksum service has a predictably
small (numeric) response message, no delegation
would take place.
A final optimization could consist in trying to
merge activities in peers providing multiple
consecutive services. Although this could greatly
reduce network traffic, it would be difficult to
analyze the improvements of this strategy if factors
such as throughput were to be weighed. The case of
the last service called (storage) is however a
particular one – if the P2P network were to be used
also as the storage medium, this service could be
directly executed by the caller peer.
6 CONCLUSIONS
In this paper, the advantages of integrating peer-to-
peer networks, service orientation and process
execution orchestration were discussed.
Based on existing frameworks and on the
previous related work from other authors, we made
some architectural analyses and presented proposals
to improve the overall efficiency which covered the
P2P network framework (dynamic discovery,
invocation, and replication) and the way BPEL
engines function (dynamic discovery, partitioning,
and delegation). The proposed enhancements can
easily fall back when the network does not support
such optimizations.
ACKNOWLEDGEMENTS
This work was funded in part by FCT – Portuguese
Foundation for Science and Technology – grant
number SFRH/BD/23976/2005.
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