posted on Wednesday, April 30, 2008 - 11:12 am
Hey, I'm trying to discover the content filter applied on the reader side ,through the writer side.Can it be done? In general, is there a datawriter for each content filter applied on the readers side?
One of the driving concepts behind DDS is that that readers and writers are decoupled as much as possible. Whether or not a Reader is using a content filter should not concern the Writer application. (Please note that a Writer always writes plain topics, a ContentFilteredTopic is just a filtered view on an existing topic that can only be applied on the Reader side. ContentFilteredTopics are therefore local to a participant and will not be transported over the network).
That said, a middleware implementation may choose to execute the filter on the writer side instead of on the reader side, since that could potentially reduce the amount of network traffic. However, such an implementation will be completely transparent to the writing application, and so there is not API on the Writer side to see which content filters have been specified on the Reader side.
Can you please explain why you would want to know about the various reader content filters in the writing application?
The fundamental philosophy with the Publish/Subscribe paradigm stresses that publishers and subscribers are completely decoupled in what is known as time, space and synchronization decoupling. Space decoupling deals with anonymous publication and subscription whereas time decoupling signifies that the interacting parties are not required to be actively participating in the interaction at the same time. This denotes that subscribers and publishers are only bound by the topic and not who is publishing/subscribing and when this occurs. “The Many Faces of Publish/Subscribe” is highly cited paper which discusses different aspects of the Publish/Subscribe paradigm. I consider this paper to be recommended reading.
Regards, Raghid Kawash
posted on Sunday, May 11, 2008 - 10:03 am
Hi, Thanks for the responces.My problem is that I need to implement a DDS Gateway that transparently P/S data types over a specific transport with very limited bandwidth. I've used the User Data Qos policy in order the pass the filter to my GWs.