Publish and Subscribe

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For the asynchronous messaging paradigm, see Publish/subscribe.

Publish and Subscribe was a document linking model introduced by Apple Computer in System 7. It extended the existing cut and paste editing model with a notification system; "subscribers" could include parts of "published" documents within themselves, and changes to the original published document would be noticed and updated by the subscribers. To the user the system was very similar to cut and paste in concept; material would be selected from the source document and published, creating an edition file, then placed into the subscriber by selecting that clipping file and positioning it inside the document.

In general terms the concept was very similar to Microsoft's Object Linking and Embedding system. Unlike OLE, P&S was comparatively complex from a programming standpoint. Suffering from second system effect, it included features intended to make it better than OLE, including support for non-rectangular areas, network notifications and an extensive user interface. A result of this complexity was poor uptake among developers, and P&S-enabled applications were few and far between. One of the few products to use it effectively was Claris's suite of software, including ClarisWorks which had already built a system somewhat similar in concept.

At the time many in the industry felt that the P&S concept was the "next big thing". Apple and Microsoft were not the only two companies trying to introduce such a system; most major software vendors attempted to introduce similar systems, and unsurprisingly NeXTSTEP included a powerful and very easy-to-implement version. However it did not take long to notice that users could find few real-world uses for the system. Further it was sometimes confusing to use; if the document included live links it was no longer possible to simply copy it to a floppy disk (for instance), the clipping file had to be copied as well. Eventually most vendors simply abandoned the concept, while Microsoft re-positioned theirs as an internet browser plugin system known as ActiveX.