2. The process of claim 1 , wherein each input item and output item comprises a character string, and wherein the library of parses comprises a plurality of semantic entities each comprising an entity class and a collection of fields, and wherein the process action of parsing the input items and the output items to produce a weighted set of parses, comprises the actions of: for each character string representing the input and output items and each semantic entity found in the library of parses, identifying a set of field matches wherein each field match comprising the longest sub-string in the input or output item character string that matches a field of a semantic entity from the library of parses, constructing a parse graph from the set of field matches such that a node exists for each character in the character string, and for each field match a field edge is directed from the node representing the starting character of the field match to the node representing the ending character of the field match, and a delimiter edge is established from each node representing a character in the character string and a node representing any next character in the character string, identifying parse paths through the parse graph, wherein each parse path comprises a sequence of nodes that starts with the node representing the first character in the character string and ends with the node representing the last character in the character string, and whose nodes are alternately connected by an edge that alternates between a field edge and a delimiter edge, such that each identified parse path comprises a sequence of semantic entity field and delimiter pairs, and for each parse path identified, computing a constraint weight factor for each identified parse path which is proportional to the number of constraints associated with the semantic entity under consideration that the parse path satisfies and the constraint weight assigned to each of the satisfied constraints, wherein each semantic entity is associated with a set of weighted constraints specifying field assignments and ordering between fields or delimiters for the semantic entity with the constraint weight of such a constraint being greater for constraints that are more likely to be exhibited by the semantic entity, computing a measure of the similarity between the parse path and each of a set of valid parse descriptors which are associated with the semantic entity, wherein each of the valid parse descriptors comprises a sequence of semantic entity field and delimiter pairs that represents a valid parsing of the semantic entity, computing a weight value for the parse path based on the constraint weight factor and valid parse descriptor similarity measure computed for the parse path, and designating the parse path to be a designated parse descriptor of the semantic entity and associating the designated parse descriptor and the computed weight value with the semantic entity to form a weighted semantic entity and parse descriptor tuple.
2. The process of claim 1 , wherein each input item and output item comprises a character string, and wherein the library of parses comprises a plurality of semantic entities each comprising an entity class and a collection of fields, and wherein the process action of parsing the input items and the output items to produce a weighted set of parses, comprises the actions of: for each character string representing the input and output items and each semantic entity found in the library of parses, identifying a set of field matches wherein each field match comprising the longest sub-string in the input or output item character string that matches a field of a semantic entity from the library of parses, constructing a parse graph from the set of field matches such that a node exists for each character in the character string, and for each field match a field edge is directed from the node representing the starting character of the field match to the node representing the ending character of the field match, and a delimiter edge is established from each node representing a character in the character string and a node representing any next character in the character string, identifying parse paths through the parse graph, wherein each parse path comprises a sequence of nodes that starts with the node representing the first character in the character string and ends with the node representing the last character in the character string, and whose nodes are alternately connected by an edge that alternates between a field edge and a delimiter edge, such that each identified parse path comprises a sequence of semantic entity field and delimiter pairs, and for each parse path identified, computing a constraint weight factor for each identified parse path which is proportional to the number of constraints associated with the semantic entity under consideration that the parse path satisfies and the constraint weight assigned to each of the satisfied constraints, wherein each semantic entity is associated with a set of weighted constraints specifying field assignments and ordering between fields or delimiters for the semantic entity with the constraint weight of such a constraint being greater for constraints that are more likely to be exhibited by the semantic entity, computing a measure of the similarity between the parse path and each of a set of valid parse descriptors which are associated with the semantic entity, wherein each of the valid parse descriptors comprises a sequence of semantic entity field and delimiter pairs that represents a valid parsing of the semantic entity, computing a weight value for the parse path based on the constraint weight factor and valid parse descriptor similarity measure computed for the parse path, and designating the parse path to be a designated parse descriptor of the semantic entity and associating the designated parse descriptor and the computed weight value with the semantic entity to form a weighted semantic entity and parse descriptor tuple. 5. The process of claim 2 , wherein the process action of computing a constraint weight factor for each identified parse path which is proportional to the number of constraints associated with the semantic entity under consideration that the parse path satisfies and the constraint weight assigned to each of the satisfied constraints, comprises an action of taking the ratio of the sum of the weights of the constraints that are satisfied by the weight of all constraints.