27. The computer-readable medium of claim 26 wherein the composition operator receives a rule, and wherein output annotations comprise text that satisfies the rule, and if an annotation in the plurality of third annotations does not include the first reference annotation or the second reference annotation or does not satisfy said rule, then no output annotation is generated by the composition operator.
26. A computer-readable medium containing instructions for controlling a computer system to perform a method of extracting information comprising: receiving a plurality of first annotations, the first annotations comprising text; processing the plurality of first annotations using a reusable extraction operator, and in accordance therewith, generating a plurality of second annotations, wherein the extraction operator identifies text in the first annotations that satisfy one or more rules or match text in a predefined list of text, and generates one or more output annotations comprising the identified text; and processing the plurality of second annotations using a reusable context operator, and in accordance therewith, generating a plurality of third annotations, the second annotations comprising text, wherein the context operator receives each of the second annotations and a reference annotation and generates output annotations comprising a plurality of text adjacent to the reference annotation; processing the plurality of third annotations using a reusable composition operator, wherein the composition operator receives each of the third annotations, one or more first reference annotations, and one or more second reference annotations, and generates output annotations comprising text between the first and second reference annotations.