Reading the final chapter 6 of the paper "The Many Faces of Publish/Subscribe" I stumbled across:
Decoupling is a desirable property because it enforces scalability at the abstraction level, by allowing participants to operate independently of one another.
At the implementation level however, scalability remains a sensitive issue, because publish/subscribe interaction can be build on top of various communication substrates and can easily be hampered by an inappropriate architecture, in particular when publish/subscribe systems are built on top of infrastructures that were not designed with scalability in mind.
Are infrastructure and architecture used interchangeably here ?
I do not understand clearly what is meant with implementation level:
⇒ Is an event service manager (distributing the events between client and server) implemented with a layered architecture an example for a “publish/subscribe systems built on top of infrastructure [...] not designed with scalability in mind” ?
If it's not what would be a good example for a publish/subscribe systems, not built on top of an scalable infrastructure?