8. A computing device, comprising: a communication device configured to: receive a speech input representing a question; and output a most-likely answer to the question; and one or more processors configured to: convert the speech input to a string of characters in a natural language; obtain tokens corresponding to the string of characters in the natural language, each token representing a potential word including at least one character of the string of characters; determine one or more part-of-speech (POS) tags for each token; determine sequences of the POS tags for the tokens, each sequence of the POS tags including one POS tag per token; determine one or more parses for each sequence of the POS tags for the tokens; determine a most-likely parse and its corresponding sequence of the POS tags for the tokens to obtain a selected parse and a selected sequence of the POS tags for the tokens by solving a maximum-a-posteriori (MAP) inference problem defined as: ( x * , y * ) = arg ⁢ ⁢ max x ∈ X , y ∈ Y ⁢ ⁢ θ T T ⁢ F ( w ) ⁢ x + θ P T ⁢ G ( x , w ) ⁢ y , where x* and y* represent a specific sequence of the POS tags and a specific parse, respectively, X represents a set of the POS tags x, Y represents a set of the parses v, θ T T represents a transformed tagging weight vector, F (w) represents a tagging feature matrix, θ P T represents a transformed parsing weight vector, and G (x,w) represents a parsing feature matrix; and determine the most-likely answer to the question using the selected parse and the selected sequence of the POS tags for the tokens.
9. The computing device of claim 8 , wherein solving the MAP inference problem comprises solving an integer linear program (ILP) defined as: max x ∈ X , y ∈ Y , z ∈ { 0 , 1 }  J  ⁢ ⁢ θ T T ⁢ F ( w ) ⁢ x + θ P T ⁢ Hz , ⁢ ∑ j ∈ J : j arc = a ⁢ ⁢ z ⁡ ( j ) = x ⁡ ( a ) ⁢ ⁢ ∀ a ∈ A , ⁢ ∑ j ∈ J : j mt = b ⁢ ⁢ z ⁡ ( j ) = y ⁡ ( b ) ⁢ ⁢ ∀ b ∈ B , and ∑ j ∈ J : j ht = b , j mod = m ⁢ ⁢ z ⁡ ( j ) = y ⁡ ( b ) ⁢ ⁢ ∀ b ∈ B , m ∈ [ n ] , where J represents a set of joint features j, each joint feature j corresponding to a head position h, a modifier position m, a trigram context t centered at the head, and a trigram context ti centered at the modifier, H represents a parsing feature matrix based on the feature matrix G x,w) but having a dependency on x removed, z represents a variable replacing cubic terms y(j arc )x(j ht )x(j mt ) with j arc =(h,m), j ht =(h,t), j mt =(m,u), and j mod =m, a represents a specific arc of a set of first-order dependency arcs A, b represents a specific trigram of a set of trigrams B, and [n] represents a set of the tokens.