I’ve never understood this as anything other than an oddly secretive power and money grab by some entrenched stakeholders in publishing and document delivery.
They seem to have non-guessable, non-hierarchy-revealing URLs that must be resolved using a database they control.
It strikes me as a showcase of ways to try to get around web standards to make things locked down.
Last time I looked at this (with horror, not with interest), the fees to become a member or to register links were exorbitant and the system itself seemed to be geared around supporting payment and DRM scenarios while making promises to fix non-existing problems (or ones that could be fixed for free using well known standard web practices).
They seem to have non-guessable, non-hierarchy-revealing URLs that must be resolved using a database they control.
It strikes me as a showcase of ways to try to get around web standards to make things locked down.
Last time I looked at this (with horror, not with interest), the fees to become a member or to register links were exorbitant and the system itself seemed to be geared around supporting payment and DRM scenarios while making promises to fix non-existing problems (or ones that could be fixed for free using well known standard web practices).