--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/service/mqtt_to_rdf/inference/inference_functions.py	Tue Jun 20 23:26:24 2023 -0700
@@ -0,0 +1,55 @@
+"""
+Some of these are from https://www.w3.org/2000/10/swap/doc/CwmBuiltins
+"""
+import urllib.parse
+from decimal import Decimal
+from typing import Optional, cast
+
+from rdflib import Literal, Namespace, URIRef
+
+from inference.candidate_binding import CandidateBinding
+from inference.lhs_evaluation import (ListFunction, SubjectFunction, SubjectObjectFunction, register)
+
+MATH = Namespace('http://www.w3.org/2000/10/swap/math#')
+ROOM = Namespace("http://projects.bigasterisk.com/room/")
+
+
+@register
+class Gt(SubjectObjectFunction):
+    pred = MATH['greaterThan']
+
+    def bind(self, existingBinding: CandidateBinding) -> Optional[CandidateBinding]:
+        [x, y] = self.getNumericOperands(existingBinding)
+        if x > y:
+            return CandidateBinding({})  # no new values; just allow matching to keep going
+
+
+@register
+class AsFarenheit(SubjectFunction):
+    pred = ROOM['asFarenheit']
+
+    def bind(self, existingBinding: CandidateBinding) -> Optional[CandidateBinding]:
+        [x] = self.getNumericOperands(existingBinding)
+        f = cast(Literal, Literal(Decimal(x) * 9 / 5 + 32))
+        return self.valueInObjectTerm(f)
+
+
+@register
+class Sum(ListFunction):
+    pred = MATH['sum']
+
+    def bind(self, existingBinding: CandidateBinding) -> Optional[CandidateBinding]:
+        f = Literal(sum(self.getNumericOperands(existingBinding)))
+        return self.valueInObjectTerm(f)
+
+
+@register
+class ChildResource(ListFunction):
+    pred = ROOM['childResource']
+
+    def bind(self, existingBinding: CandidateBinding) -> Optional[CandidateBinding]:
+        ops = self.getOperandNodes(existingBinding)
+        if len(ops) != 2 or not isinstance(ops[0], URIRef) or not isinstance(ops[1], Literal):
+            raise ValueError(f'expected (?baseUri ?nextSegmentString) as subject to {self}')
+        newUri = URIRef(ops[0].rstrip('/') + '/' + urllib.parse.quote(ops[1].toPython(), safe=''))
+        return self.valueInObjectTerm(newUri)