Hi Niclas Central in the Jini metaphor is that service are not always available and the > 'client' always has to support this, whereas in Merlin the total opposite is > true. So I have recognized that there has to be some form of Availability > noitification system introduced, and I haven't gotten to defining one. Once > that is in place, we not only get the Jini/Distributed services possibility, > but also reloadable components, which is desirable independently of > Jini/distrbuted.
You are touching some very interesting thing "Availability noitification system ". a. The question is whose responsibility is to ensure the availibilty and the availibility notification, the component itself or the container of the component? If the container is responsible, then the container should check for the availibity of the components it is responsible for. The container could do it periodically by a timer or more intelligently by having an management agent. On the other hand, if the component takes the responsibility, then it prompotes a proactive component architecture. I think both approaches are interesting, and probably completing each other. b. The second issue is how the client should know about the availibility? Should the client be informed by the I-the component II-the container of the component III- should the client proactively ask for the availibility? I- results in observer/oberservable pattern that we know from Java's know listener mechanism. As far as I can see, this approach has been taken in Merlin's Kernel.java II- here a simple hub-spoke architecture might be good enough, where the container (or an underlying component) acts like the hub. Both publishers (the component) and subscribers (the client) of availibility event act as spokes. Note that this approach could also be used for a. III- well, this is the difficult one to implement. Here the client could periodically either ask the component or the container of the compoent about the availibility. Having said the above, it seems to me that Merlin is not geared toward distributed systems? Best Regards -- Nader Aeinehchi Aasenhagen 66 E 2020 Skedsmokorset NORWAY Direct and Mobile +47 41 44 29 57 Tel (private): +47 64 83 09 08 Fax +47 64 83 08 07 www.aeinehchi.com ----- Original Message ----- From: "Niclas Hedhman" <[EMAIL PROTECTED]> To: "Avalon Developers List" <[EMAIL PROTECTED]> Sent: Saturday, April 03, 2004 12:07 PM Subject: Re: What do you think about Merlin with Jini? > On Saturday 03 April 2004 17:43, Nader Aeinehchi wrote: > > 1. Is there any > > automatization in discovery of the deployed elements? > > The Composition package reads the block.xml file(s) and builds a model of the > involved components, matches any dependencies and tries to figure out what > ties into what (that has a good chance of being deployed). > > >2. What do you think to either integrate with > > Jini or develop a similar mechanism in Merlin? > > There has been some debate of "Jini in Avalon", and since I am probably one of > the more experience Jini users, I guess it falls onto my responsibility to > figure out how this can be achieved, > > Central in the Jini metaphor is that service are not always available and the > 'client' always has to support this, whereas in Merlin the total opposite is > true. So I have recognized that there has to be some form of Availability > noitification system introduced, and I haven't gotten to defining one. Once > that is in place, we not only get the Jini/Distributed services possibility, > but also reloadable components, which is desirable independently of > Jini/distrbuted. > > Once that is in place, it is a matter of moving forward. > > > Niclas > -- > +---------//-------------------+ > | http://www.bali.ac | > | http://niclas.hedhman.org | > +------//----------------------+ > > --------------------------------------------------------------------- > To unsubscribe, e-mail: [EMAIL PROTECTED] > For additional commands, e-mail: [EMAIL PROTECTED] --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
