[cap-talk] Regarding AMQP Messaging paradigm and pattern in E-Lang

[Karp, Alan H]

Tom Van Cutsem wrote:


è I didn't solve the security issues, however. In section 4.7 I explicitly describe AmbientTalk's shortcomings w.r.t. security, in particular w.r.t. it's service discovery mechanism (cf. p90). Because AmbientTalk was designed for ad hoc networks (networks without infrastructure), we could not rely upon a third party to act as an introducer between mutually suspicious distributed objects. Essentially, objects discover each other directly via an interface type, but any object has the ability to define or refer to such interfaces. Hence, once an object allows itself to be discovered through service discovery, any object can discover it.

We addressed this problem in e-speak using a publish-distribute-subscribe model.  While the distributor could be a trusted third party, it could also be a facet on the publisher.  Our discovery was based on a Vocabulary, an object consisting of key-value pairs, rather than an interface type.  The key difference is that you need a capability to a Vocabulary to advertise or find objects advertised in it, which gave us control over who could publish and subscribe to events of a particular type.  The Vocabulary also served as an interface type because the event state was specified as values in the Vocabulary and the subscription request was expressed as a constraint expression in that Vocabulary.

________________________
Alan Karp
Principal Scientist
Virus Safe Computing Initiative
Hewlett-Packard Laboratories
1501 Page Mill Road
Palo Alto, CA 94304
(650) 857-3967, fax (650) 857-7029
http://www.hpl.hp.com/personal/Alan_Karp
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