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Structure of Expert Systems
Forward and Backward Chaining
Below are rules for an Expert System used to identify animals. Read through and then complete the activity at the end which looks at the difference between forward and backward chaining.
| Rule 1 | IF THEN |
animal has backbone vertebrate |
| Rule 2 | IF THEN |
animal does not have backbone invertebrate |
| Rule 3 | IF AND THEN |
animal is vertebrate has hair mammal |
| Rule 4 | IF AND THEN |
animal is vertebrate produces milk mammal |
| Rule 5 | IF AND THEN |
animal is invertebrate has exoskeleton arthropod |
| Rule 6 | IF AND THEN |
animal is invertebrate has jointed limbs arthropod |
| Rule 7 | IF AND THEN |
animal is arthropod six legs insect |
| Rule 8 | IF AND AND THEN |
animal is arthropod has three main body parts has antennae insect |
| Rule 9 | IF AND THEN |
animal is arthropod does not have antennae arachnid |
| Rule 10 | IF AND THEN |
animal is arthropod has two body parts arachnid |
| Rule 11 | IF AND THEN |
animal is arachnid eight legs spider |
| Rule 12 | IF AND AND THEN |
animal is insect triangular shaped head elliptical shaped body cockroach |
| Rule 13 | IF AND AND THEN |
animal is insect has wings and bulky body active at night and antennae without clubbed tips moth |
| Rule 14 | IF AND AND THEN |
animal is insect has wings and slender body active during day and antennae with clubbed tips butterfly |
| Rule 15 | IF AND AND THEN |
animal is spider shiny carapace four spinnerets funnel web |
| Rule 16 | IF AND AND THEN |
animal is spider red/orange stripe on abdomen slender black/brown legs red back |
| Rule 17 | IF AND AND THEN |
animal is spider cylindrical shape white spot at tip of abdomen white-tailed |
- Given that the following is contained in the database of facts, establish by forwarding chaining that the animal is a cockroach.
- animal has no backbone
- animal has an exoskeleton
- animal has three main body parts
- animal has a triagular shaped head
- animal has an elliptical shaped body
- animal has antennae
- Given that the following is contained in the database of facts, establish by backward chaining that the animal is a funnel web. Remember, you start with the goal - the animal is a funnel web (Rule 15) and work backwards.
- animal has no backbone
- animal has jointed limbs
- animal has no antennae
- animal has eight legs
- animal has shiny carapace
- animal has four spinnerets
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