Evidence files in LoMRF are text files having the suffix
file_name.db). The contents of an evidence file
are ground predicates (facts) and optionally ground function Mappings.
A function mapping defines a possible true grounding of a function (see Function Definitions). Syntactically follows the corresponding function definition in the knowledge base file, but the domain types are replaced with some of their corresponding constant symbols.
For example, the true possible groundings of the function
time = next(time) are the following:
2 = next(1) 3 = next(2) 4 = next(3) 5 = next(4) 6 = next(5) 7 = next(6) 8 = next(7) 9 = next(8) 10 = next(9)
According to the given true groundings in the example above,
next(1) results to the constant
LoMRF takes a Closed-world assumption approach for function
mappings and therefore mappings that are not defined in the evidence are implicitly assumed as false. For example,
the mapping of
next(0) is missing from the above evidence, thus it is implicitly assumed as false.
Facts (ground predicates)
Ground predicates in the evidence represent known facts for the LoMRF. Each fact is expressed with predicates that contain only constants from their corresponding domains. Each fact represents a true grounding of a specific predicate, optionally facts can be negated and thus represent a false grounding of a predicate.
For example, the following ground predicates are facts that express that Agamemnon and Menelaus are brothers, but Achilles is not brother of Agamemnon.
Brother(Agamemnon, Menelaus) Brother(Menelaus, Agamemnon) !Brother(Achilles, Agamemnon)
By default LoMRF takes Closed-world assumption for all
instantiations of predicates that have at least one fact in the specified evidence file, unless it is explicitly
specified to take Open-world assumption in the inference
options or it is a query predicate (see Inference). Therefore, we can define only the true
groundings in the evidence and assume a False state for all other possible combinations (e.g.,
Brother(Achilles, Menelaus) is implicitly assumed as False).