System and method for automatic matching of contracts using a fixed-length predicate representation
An item of inventory is described as a Boolean expression, which is converted into a multi-level, alternating AND/OR impression tree representation with leaf nodes representing conjuncts. Processing the conjuncts of the tree through a contract index results in retrieving a set of candidate contracts that match at least some but not necessarily all impression tree leaf node predicates. Next, an AND/OR contract tree representation is constructed with each contract tree leaf node having a label representing a projection onto a discrete set of ordered symbols. Contracts with projections that cover the entire range of discrete set of ordered symbols are deemed to satisfy the item of inventory. Implementation of the contract index includes retrieval techniques to support multi-valued predicates as well as confidence threshold functions using a multi-level tree representation of multi-valued predicates.
1. A computer-implemented method for matching of contracts using a fixed-length complex predicate representation comprising:
storing, in memory, an impression opportunity profile in the form of a Boolean expression;
converting the impression opportunity profile into a list comprising at least one impression conjunct;
retrieving, at a server, a set of candidate contracts that match the at least one impression conjunct;
constructing, within a computer memory, a contract tree representation of at least one contract from among the set of candidate contracts, the contract tree comprising alternating AND/OR levels of a plurality of nodes, the plurality of nodes comprising at least one contract tree leaf node predicate, the contract tree leaf node predicates having a label representing a projection onto a discrete set of ordered symbols; and
marking, for producing at least one marked contract tree leaf node predicate, the at least one contract tree leaf node predicate based on comparing the at least one contract tree leaf node predicate to the at least one impression conjunct.
2. The method of claim 1 , further comprising assembling a set of satisfying contracts where the projecting results in a contiguous projection over the discrete set of ordered symbols.
3. The method of claim 1 , wherein the retrieving includes using an inverted index of contracts.
4. The method of claim 1 , wherein the at least one of the set of candidate contracts includes a pair of numbers for representing a position in the inverted index of contracts.
5. The method of claim 1 , wherein the inverted index of contracts includes a weighting coefficient corresponding to at least one contract tree leaf node predicate.
6. The method of claim 1 , wherein the inverted index of contracts includes making posting lists of contracts for IN predicates.
7. The method of claim 1 , wherein the impression opportunity profile in the form of a Boolean expression is specified comprising a disjunctive normal form representation.
8. The method of claim 1 , wherein the impression opportunity profile in the form of a Boolean expression is specified comprising a conjunctive normal form representation.
9. The method of claim 1 , wherein the impression opportunity profile in the form of a Boolean expression is specified comprising a vector of feature-value pairs.
10. The method of claim 1 , wherein the inverted index of contracts includes an upper bound weight.
11. The method of claim 1 , wherein the inverted index of contracts includes making posting lists of contracts for NOT-IN predicates.
12. The method of claim 1 , wherein the retrieving operation retrieves a set containing only the top N weighted contracts.
13. The method of claim 1 , wherein the retrieving operation prunes contracts containing any NOT-IN predicates violated by the impression opportunity profile.
14. An ad server network for matching of contracts using a fixed-length complex predicate representation comprising:
a memory to store an impression opportunity profile in the form of a Boolean expression;
a processing unit to convert the impression opportunity profile into a list comprising at least one impression conjunct;
a module to retrieve a set of candidate contracts that match the at least one impression conjunct;
a module to construct a contract tree representation of at least one contract from among the set of candidate contracts, the contract tree comprising alternating AND/OR levels of a plurality of nodes, the plurality of nodes comprising at least one contract tree leaf node predicate, each contract tree leaf node predicate having a label representing a projection onto a discrete set of ordered symbols; and
a module to produce at least one marked contract tree leaf node predicate, the at least one contract tree leaf node predicate based on comparing the at least one contract tree leaf node predicate to the at least one impression conjunct.
15. The ad server network of claim 14 , further comprising assembling a set of satisfying contracts where the projecting results in a contiguous projection over the discrete set of ordered symbols.
16. The ad server network of claim 14 , wherein the retrieving includes using an inverted index of contracts.
17. The ad server network of claim 16 , wherein the inverted index of contracts includes posting lists of contracts for IN predicates.
18. The ad server network of claim 14 , wherein the set of candidate contracts containing only top N weighted contracts.
19. The ad server network of claim 14 , wherein the at least one of the set of candidate contracts includes a pair of numbers for representing a position of the at least one of the set of selected contracts in an index.
20. The ad server network of claim 14 , wherein the impression opportunity profile includes a description containing at least one of, disjunctive normal form representation, conjunctive normal form representation.