Jan Algermissen wrote: > >> Some of the definitions I've come across for a Service are: > > > IMHO, substitutability (of one service by another) is an important > concept. If you go to shoe order processor A and find it is down, you > can equally well turn to shoe order processor B, given you know they > are substitutable. > > A real world example is that you can use another Web search engine if > your favorite one is down, because you happen to know that they are > both Web search engines.
One of the important concepts in SOA is exactly this. You have to be able to tell that a service can substitute for another. When you have 4 types of services and 2 of each are visible on the network, you can reach a certain comfort level by hardcoding the relationships so that your software knows which is primary and which is backup. When you get into 100s or 1000s of services in your SOA, you really need a much more limber mechanism. Jini's service lookup uses Java interfaces as an available detail for resolving services that match your request. This will always provide you a 100% guarentee of the service meeting your requirements for programatic use. The Entry objects that can be included with the service registration provide a mechanism for qualifying the look up further. As I've discussed here before, you can also include other data in Entry objects, include code that might proxy your services access to the Java RMI world. JERI security provides the means for you to trust that random deployments (including test deployments) don't get used by your production systems. You can declare that a service must authenticate with particular principals, or that code must be signed in a particular way, or you can event use the HTTPMD protocol for downloading code to control what specific version of an implementation you use. Web Services still has quite a ways to go to reach this level of control and scalability. Gregg Wonderly ------------------------ Yahoo! Groups Sponsor --------------------~--> Get Bzzzy! (real tools to help you find a job). Welcome to the Sweet Life. http://us.click.yahoo.com/A77XvD/vlQLAA/TtwFAA/NhFolB/TM --------------------------------------------------------------------~-> Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/service-orientated-architecture/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
