Concept learning is a form of supervised machine learning that operates on knowledge bases in description logics. State-of-the-art concept learners often rely on an iterative search through a countably infinite concept space. In each iteration, they retrieve instances of candidate solutions to select the best concept for the next iteration. While simple learning problems might require a few dozen instance retrieval calls to find a fitting solution, complex learning problems might necessitate thousands of calls. We alleviate the resulting runtime challenge by presenting a semantics-aware caching approach. Our cache is essentially a subsumption-aware map that links concepts to a set of instances via crisp set operations. Our experiments on 5 datasets with 4 symbolic reasoners, a neuro-symbolic reasoner, and 5 popular pagination policies demonstrate that our cache can reduce the runtime of concept retrieval and concept learning by an order of magnitude while being effective for both symbolic and neuro-symbolic reasoners.
Figures & tables
Construct
Syntax
Semantics
Atomic concept
A
AI⊆ΔI
Atomic role
r
rI⊆ΔI×ΔI
Top concept
⊤
ΔI
Bottom concept
⊥
∅
Negation
¬C
ΔI∖CI
Conjunction
C⊓D
CI∩DI
Table 1: Syntax & semantics for ALC concepts. I stands for an interpretation with domain ΔI .
Dataset
∣ Ind. ∣
∣ Classes ∣
∣ Prop. ∣
∣TBox∣
∣ABox∣
∣NC∣
Vicodi
33,238
194
10
204
116,181
2,105
Carcinogenesis
22,372
142
0 4
144
0 74,223
1,684
Mutagenesis
14,145
0 86
0 5
0 82
0 47,722
1,572
Family
00 202
0 18
0 4
0 26
000 472
1,236
Table 2: Datasets statistics. ∣NC∣ is the total number of concepts generated on each dataset. ∣ Ind. ∣ is the total number of individuals and ∣ Prop. ∣ is the total number of properties (relations) in each dataset.
Figure 1: Average runtime of concept learners using no cache, the semantic cache, and the non-semantic cache baseline across different datasets.
Figure 2: Run time performance vs cache size for five reasoners on large datasets. The dotted horizontal lines represent the baseline performance of each reasoner without caching.
Figure 5Figure 6
Figure 7: Average physical memory usage of concept learners using the semantic cache, and the non-semantic cache baseline across different datasets.