An HL support is a type of support that is a way of packaging up justifications that are either impractical or impossible to manifest. A single HL support can represent multiple justifications, sometimes numbering in the thousands or millions. Some HL supports are guaranteed to bottom out in a justification consisting of only assertions. Others represent reasoning that is implemented in code.
HL-supports within the Cyc system come in three types of flavors, which can be schematically depicted as:
generalized-hl-support-p
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hl-support-p kb-hl-support-p reified-hl-support-gaf?
The first flavor described by HL-SUPPORT-P is essentially a support obtained from deductions already existing in the KB. Of the three types, this one is the oldest and predates a lot of newer development and architectural choices.
The second flavor is KB-HL-SUPPORT-P and is an HL-support wrapped by a KB-HL-support object. KB-HL-support object is used to improve indexing and caching, thereby making the TMS process faster.
The third flavor is REIFIED-HL-SUPPORT-GAF. This type essentially contains HL-supports which come in the form of assertions in the KB.