15. A non-transitory, computer readable medium embodied in a tangible form including executable computer program code operable to determine a robust wrapper representing a data item of a plurality of data items in a document represented by a markup language, wherein the computer readable medium includes: executable computer code operable to develop, based on archival data representative of a temporal history of the document, a model indicative of the temporal history; executable computer code operable to determine, based on the developed model, robustness characteristics for a plurality of different wrappers representing associated paths to the data item in a representation of the document, the robustness characteristics for each wrapper representing a likelihood that the corresponding wrapper will continue to be effective for extracting the data item when the document changes, wherein the representation of the document relates to a tree having a plurality of nodes, and wherein the temporal history of the document relates at least to an original tree and a plurality of changed trees indicative of trees that appeared during the temporal history of the document that are different from the original tree; and executable computer code operable to provide, based on a result of the determining operation, as a result wrapper, one of the plurality of wrappers that has a desired robustness characteristic; wherein the executable computer code operable to develop the model includes: executable computer code operable to obtain a plurality of pairs, each one of the plurality of pairs including a first element (T) and a second element (T′), wherein T is the original tree and T′ is a different one of the plurality of changed trees; executable computer code operable to determine a plurality of different change operations indicative of changes made to change T into T′ for each one of the plurality of pairs; and executable computer code operable to associate each one of the plurality of different change operations with a probability value indicative of a probability that the associated change operation is applied to the document.
15. A non-transitory, computer readable medium embodied in a tangible form including executable computer program code operable to determine a robust wrapper representing a data item of a plurality of data items in a document represented by a markup language, wherein the computer readable medium includes: executable computer code operable to develop, based on archival data representative of a temporal history of the document, a model indicative of the temporal history; executable computer code operable to determine, based on the developed model, robustness characteristics for a plurality of different wrappers representing associated paths to the data item in a representation of the document, the robustness characteristics for each wrapper representing a likelihood that the corresponding wrapper will continue to be effective for extracting the data item when the document changes, wherein the representation of the document relates to a tree having a plurality of nodes, and wherein the temporal history of the document relates at least to an original tree and a plurality of changed trees indicative of trees that appeared during the temporal history of the document that are different from the original tree; and executable computer code operable to provide, based on a result of the determining operation, as a result wrapper, one of the plurality of wrappers that has a desired robustness characteristic; wherein the executable computer code operable to develop the model includes: executable computer code operable to obtain a plurality of pairs, each one of the plurality of pairs including a first element (T) and a second element (T′), wherein T is the original tree and T′ is a different one of the plurality of changed trees; executable computer code operable to determine a plurality of different change operations indicative of changes made to change T into T′ for each one of the plurality of pairs; and executable computer code operable to associate each one of the plurality of different change operations with a probability value indicative of a probability that the associated change operation is applied to the document. 17. The computer readable medium of claim 15 , wherein the computer readable medium further includes: executable computer code operable to evaluate the plurality of wrappers to determine whether the path associated with each wrapper leads to the data item in the document when the document is changed in accordance with the plurality of different change operations; executable computer code operable to determine, based on a result from the evaluation of the plurality of wrappers and the probability values associated with the plurality of different change operations, a success/failure probability for each one of the wrappers.