The lack of standards currently in the business rules space makes interoperability hard. Although many of the technical deployment standards are supported as deployment options by rules vendors, the standards specific to rules are limited:
JSR-94 - some information on this first rules standard can be found at javarules.org. It is a fairly limited standard but fairly well supported by the major vendors.
OMG Production Rules Representation - a standard for rule interchange under development by the OMG. More details on their site.
W3C Rules Interchange Format - another standard under development by W3C. More information here.
Hopefully the OMG and W3C ones will come together. It is also worth noting that these standards lack end-user customer participation so those interested should think about signing up.
In answer to the questions posed in the comments:
- The leading vendors are active in both standards. Doubt they would invest the time if they weren't planning on supporting them. I suspect that failure to merge them might result in one getting more support than the other but all the big vendors would be likely to support both at some level.
- As for what customers can do - participate in the standards! Join OMG or W3C and get on these committees. Get your point of view across.
RDF has also been proposed but it seems more likely that a combined rules-specific standard will be the way this goes.