SIPE-2's sort hierarchy supports OKBC (earlier versions supported GFP), and thus permits use of the GKB-Editor. Using OKBC, the system can generate plans with all knowledge base references going to an external knowledge base that supports OKBC. Several different frame systems, including LOOM and THEO, support OKBC.
Producing large plans using LOOM to store the SIPE-2 KB slows the planning process significantly. Efficiency considerations may require first translating the relevant parts of the external KB into SIPE-2's internal representation.