A processing device executing a rule engine receives a first object. The processing device determines whether the first object is represented by a relational model or an object-oriented model. The first object is determined to be represented by the relational model responsive to the first object lacking a reference to a nested object. The first object is determined to be represented by the object-oriented model responsive to the first object including a reference to a nested object. If the first object is represented by the relational model, a join is performed between the first object and a second object based on a relationship between the objects using a first node. If the first object is represented by the object-oriented model, an expression of the first object is evaluated to navigate to a third object that is a first nested object of the first object using a second node.
Please help me write a proper abstract based on the patent claims. CLAIM: 1. A method comprising: receiving a first object by a processing device executing a rule engine; determining, by the processing device, whether the first object is represented by a relational model or an object-oriented model, wherein the first object is determined to be represented by the relational model responsive to the first object lacking a reference to a nested object, and wherein the first object is determined to be represented by the object-oriented model responsive to the first object comprising a reference to a nested object; responsive to determining that the first object is represented by the relational model, performing a join between the first object and a second object based on a relationship between the first object and the second object using a first node, wherein the first node comprises a left input that receives the first object and a right input that receives the second object; and responsive to determining that the first object is represented by the object-oriented model, evaluating an expression of the first object to navigate to a third object that is a first nested object of the first object using a second node, wherein the second node comprises a single input that receives the first object. 2. The method of claim 1, further comprising: inserting, by the second node, a callback into the third object. 3. The method of claim 2, further comprising: responsive to an update to the first object, propagating, by the second node, the update to the third object using the callback; and reevaluating the expression of the first object using the second node. 4. The method of claim 3, further comprising notifying one or more children nodes associated with the second node of the update. 5. The method of claim 1, wherein the first object represented by the object-oriented model comprises a hierarchical data structure. 6. The method of claim 1, wherein the rule engine comprises a Rete rule engine. 7. The method of claim 1, further comprising: generating a network comprising a plurality of nodes by: generating the first node comprising the left input and the right input; and generating the second node comprises the single input; and generating respective data structures for each of the first node and the second node. 8. The method of claim 1, further comprising: receiving the first object at a terminal node; propagating the first object to an output of the terminal node using the terminal node; determining a rule associated with the first object; and scheduling execution of the rule. 9. A system comprising a memory; and a processing device, operatively coupled to the memory, to: receive a first object by a processing device executing a rule engine; determine whether the first object is represented by a relational model or an object-oriented model, wherein the first object is determined to be represented by the relational model responsive to the first object lacking a reference to a nested object, and wherein the first object is determined to be represented by the object-oriented model responsive to the first object comprising a reference to a nested object; responsive to determining that the first object is represented by the relational model, perform a join between the first object and a second object based on a relationship between the first object and the second object using a first node, wherein the first node comprises a left input that receives the first object and a right input that receives the second object; and responsive to determining that the first object is represented by the object-oriented model, evaluate an expression of the first object to navigate to a third object that is a first nested object of the first object using a second node, wherein the second node comprises a single input that receives the first object. 10. The system of claim 9, wherein the processing device is further to: insert, by the second node, a callback into the third object. 11. The system of claim 10, wherein the processing device is further to: responsive to an update to the first object, propagate, by the second node, the update to the third object using the callback; and reevaluate the expression of the first object using the second node. 12. The system of claim 11, wherein the processing device is further to notify one or more children nodes associated with the second node of the update. 13. The system of claim 9, wherein the first object represented by the object-oriented model comprises a hierarchical data structure. 14. The system of claim 9, wherein the rule engine comprises a Rete rule engine. 15. The system of claim 9, wherein the processing device is further to: generate a network comprising a plurality of nodes, wherein to generate the network the processing device is further to: generate the first node comprising the left input and the right input; and generate the second node comprises the single input; and generate respective data structures for each of the first node and the second node. 16. A non-transitory computer readable storage medium comprising instructions that, when executed by a processing device, cause the processing device to: receive, by the processing device, a first object by a processing device executing a rule engine; determine, by the processing device, whether the first object is represented by a relational model or an object-oriented model, wherein the first object is determined to be represented by the relational model responsive to the first object lacking a reference to a nested object, and wherein the first object is determined to be represented by the object-oriented model responsive to the first object comprising a reference to a nested object; responsive to determining that the first object is represented by the relational model, perform, by the processing device, a join between the first object and a second object based on a relationship between the first object and the second object using a first node, wherein the first node comprises a left input that receives the first object and a right input that receives the second object; and responsive to determining that the first object is represented by the object-oriented model, evaluate, by the processing device, an expression of the first object to navigate to a third object that is a first nested object of the first object using a second node, wherein the second node comprises a single input that receives the first object. 17. The non-transitory computer readable storage medium of claim 16, including further instructions that, when executed by the processing device, cause the processing device to: insert, by the second node, a callback into the third object. 18. The non-transitory computer readable storage medium of claim 17, including further instructions that, when executed by the processing device, cause the processing device to: responsive to an update to the first object, propagate, by the second node, the update to the third object using the callback; and reevaluate the expression of the first object using the second node. 19. The non-transitory computer readable storage medium of claim 17, including further instructions that, when executed by the processing device, cause the processing device to notify one or more children nodes associated with the second node of the update. 20. The non-transitory computer readable storage medium of claim 16, wherein the first object represented by the object-oriented model comprises a hierarchical data structure.