9. The information retrieval apparatus of claim 7 , wherein the contextual constraint comprises one or more local keywords, and wherein the comparison of the contextual constraint with the extracted contextual information includes finding a match between the extracted contextual information and said local keywords, and wherein the at least one positional relationship comprises a measure of proximity of said local key word match relative to the indexed item of numerical data within text of the source document.
9. The information retrieval apparatus of claim 7 , wherein the contextual constraint comprises one or more local keywords, and wherein the comparison of the contextual constraint with the extracted contextual information includes finding a match between the extracted contextual information and said local keywords, and wherein the at least one positional relationship comprises a measure of proximity of said local key word match relative to the indexed item of numerical data within text of the source document. 10. The information retrieval apparatus of claim 9 , wherein the measure of proximity reflects one or more of: a number of words separating the represented item of numerical data from the local keyword match, and punctuation separating the represented item of numerical data from the local keyword match.