Re: Using RDDL as a Distributed Registry Architecture
[Thanks to everyone for their input. As always, I am deeply impressed by the incredible brainpower on this list.] I have carefully read all your comments and have attempted to incorporate them into a more compelling argument. Here are the (revised) key points to my argument: 1. Defining characteristics of the Web: - extreme scalability - highly decentralized, distributed 2. My client's current approach is to create an ebXML-based Registry containing information about all the services it supports. The registry is a centralized, heavyweight data pool where users go to find the who, what, and where of services. [Note that UDDI has the same centralized, heavyweight mentality.] 3. A centralized, heavyweight Registry suffers from several problems: - Non-scalable: as new services are added the Registry grows, the number of users also grows, and the load on the Registy correspondingly increases - Single point of failure (unreliable): if the Registy fails then all users are impacted. 4. A centralized Registry is a double-edged sword in terms of security: - there is a single point of attack, so intruders can focus their efforts on the one system - there is a single point to secure, so efforts to secure the system can be focused There is an alternative to a centralized, heavyweight Registry ... 5. RDDL (Resource Directory Description Language) is a lightweight, distributed mechanism for storing information about a namespace. The key notion of RDDL is to use namespaces in a dual role - both as an identifier, and as a pointer to a RDDL document. The RDDL document is a directory for the namespace. That is, it contains pointers to documents that you wish to associate with the namespace. Such documents include schemas, stylesheets, dictionary, spec (all the things that my client wants associated with each service in his registry). 6. I propose that each client service be associated with a different namespace, and each namespace point to a RDDL document. Thus, the set of client metadata is distributed across all the RDDL documents. This yields a lightweight, distributed metadata mechanism. 7. A decentralized, lightweight RDDL-based registy has the benefits of: - Scalable: new RDDL directories can be deployed without impact to the performance of the system as a whole - Reliable: even if one RDDL directory fails the other parts remain active - Local control of local resources (independent, evolutionary): maintainers of each RDDL collection has authority over their work, and can evolve it indedendently of others This approach is consistent with the Web architecture. 8. A decentralized Registry is a double-edged sword in terms of security: - there is no single point to attack, so intruders are forced to disperse their efforts over many systems - each RDDL system must devise their own security mechanisms 9. In a RDDL-based, distributed architecture services are located using a search engine. An interesting aspect of RDDL is that a RDDL document has both a machine interface as well as a human (eyeball) interface. Consequently, the searching can be done using either a browser or a robot. 10. I believe that the benefits of a decentralized, RDDL-base Registry require us to explore this as a viable alternative to centralized, heavyweight UDDI- or ebXML-based Registries.
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