32. A two-level document processing method preparing a downstream document on the basis of an upstream document, and an upstream document on the basis of a downstream document, said method comprising the steps of: comparing the upstream document with an upstream deletion document including information which is particular to the upstream document and is unnecessary for the downstream document; selecting, from the upstream document and based on results of the step of comparing, a deletion candidate to be deleted from the upstream document until no more deletion candidate is found; searching said upstream deletion document for corresponding information corresponding to the deletion candidate; displaying, if the corresponding information is present in the upstream deletion document, the deletion candidate and the corresponding information to have approval of deletion; deleting the deletion candidate from the upstream document if the deletion of the deletion candidate is approved; storing the deletion candidate and the corresponding information into a deletion file after the deletion of the deletion candidate; storing the deletion candidate and the corresponding information into a non-deletion file without deleting the deletion candidate from the upstream document if the deletion of the deletion candidate is not approved; storing the deletion candidate into an upstream special candidate file without deleting the deletion candidate from the upstream document, if the corresponding information corresponding to the deletion candidate is absent in the upstream deletion document; comparing the upstream document with a downstream addition document including information which is particular to the downstream document and is unnecessary for the upstream document; selecting, from the downstream addition document and based on the results of the step of comparing, an addition candidate to be added to the upstream document until no more addition candidate is found; searching said downstream addition document for corresponding information corresponding to the addition candidate; displaying, if the corresponding information is present in the downstream addition document, the addition candidate and the corresponding information to have approval of addition; adding the addition candidate to the upstream document if the addition of the addition candidate is approved; storing the addition candidate and the corresponding information into an addition file; storing the addition candidate and the corresponding information into a non-addition file without adding the addition candidate to the upstream document, if the addition of the addition candidate is not approved; storing the addition candidate into a downstream special candidate file without adding the addition candidate to the upstream document, if the corresponding information corresponding to the addition candidate is absent in the downstream addition document; outputting the input upstream document and the output downstream document contrastively in order to clarify the addition and deletion portions; comparing the downstream document with a downstream deletion document including information which is particular to the downstream document and is unnecessary for the upstream document; selecting, from the downstream deletion document and based on results of the step of comparing, a deletion candidate to be deleted from the downstream document until no more deletion candidate is found; searching the downstream deletion document for corresponding information corresponding to the deletion candidate; displaying, if the corresponding information is present in the downstream deletion document, the deletion candidate and the corresponding information to have approval of deletion; deleting the deletion candidate from the downstream document if the deletion of the deletion candidate is approved; storing the deletion candidate and the corresponding information into a deletion file; storing the deletion candidate and the corresponding information into a non-deletion file without deleting the deletion candidate from the downstream document, if the deletion of the deletion candidate is not approved; storing the deletion candidate into a downstream special candidate file without deleting the deletion candidate from the downstream document, if the corresponding information corresponding to the deletion candidate is absent in the downstream deletion document; comparing the downstream document with an upstream addition document including information which is particular to the upstream document and is unnecessary for the downstream document; selecting, from the upstream addition document and based on results of the step of comparing, an addition candidate to be added to the downstream document until no more addition candidate is found; searching the upstream addition document for corresponding information corresponding to the addition candidate; displaying, if the corresponding information is present in the upstream addition document, the addition candidate and the corresponding information to have approval of addition; adding the addition candidate to the downstream document if the addition of the addition candidate is approved; storing the addition candidate and the corresponding information into an addition file; storing the addition candidate and the corresponding information into a non-addition file without adding the addition candidate to the downstream document if the addition of the addition candidate is not approved; storing the addition candidate into an upstream special candidate file without adding the addition candidate to the downstream document, if the corresponding information corresponding to the addition candidate is absent in the upstream addition document; outputting the input downstream document and the output upstream document contrastively in order to clarify the addition and deletion portions; selecting shortage candidate from an upstream document under shortage decision rules used as a reference to decide whether some kinds of information are lacking or not; searching an upstream addition/deletion document for corresponding information corresponding to the shortage candidate; repeating the steps of selecting and searching until no more shortage candidate is found in said upstream document; storing the shortage candidate and the corresponding information into an excessive deletion file under a decision that an excessive deletion has been made if the corresponding information corresponding to the shortage candidate is present in the upstream addition/deletion document; adding the corresponding information to the upstream document, and deleting the corresponding information from the upstream addition/deletion document, searching a repository for the corresponding information corresponding to the shortage candidate if the corresponding information is not present in the upstream addition/deletion document, said repository being resources of information; adding the corresponding information to the upstream document, and storing the shortage candidate and the corresponding information to an addition file, if the corresponding information is present in the repository, and if the addition of the corresponding information is decided to be reasonable; storing the shortage candidate and the corresponding information into a non-addition file without adding the corresponding information to the upstream document, if the corresponding information is present in the repository, and the addition of the corresponding information is decided to be unreasonable; storing the shortage candidate into an upstream shortage candidate file without adding the corresponding information to the upstream document, if the corresponding information is absent in the repository; selecting an excessive candidate from an upstream document under excess decision rules used as a reference to decide whether some kinds of information are excessive or not, after no more shortage candidate is found in the upstream document under shortage decision rules; searching an upstream addition/deletion document for corresponding information corresponding to the excessive candidate, said upstream addition/deletion document storing information which is present in the upstream document and is absent in the downstream document; repeating the steps of selecting and searching until no more excessive candidate is found in said upstream document; storing the excessive candidate and the corresponding information into an excessive addition file under a decision that an excessive addition has been made, if the corresponding information corresponding to the excessive candidate is present in the upstream addition/deletion document; deleting the excessive candidate from the upstream document, and deleting the corresponding information from the upstream addition/deletion document after storing the excessive addition; deleting the excessive candidate from the upstream document and storing the excessive candidate into a deletion file, if the corresponding information corresponding to the excessive candidate is absent in the upstream addition/deletion document, and if the deletion of the excessive candidate is decided to be reasonable; storing the excessive candidate into a non-deletion file without deleting the excessive candidate from the upstream document, if the corresponding information corresponding to the excessive document is absent in the upstream addition/deletion document, and the deletion of the excessive candidate is decided to be unreasonable; outputting the upstream document and the upstream addition/deletion document contrastively in order to clarity the addition and deletion portions before and after refinement; selecting shortage candidate from an downstream document under shortage decision rules used as a reference to decide whether some kinds of information are lacking or not; searching an downstream addition/deletion document for corresponding information corresponding to the shortage candidate; repeating the steps of selecting and searching until no more shortage candidate is found in said downstream document; storing the shortage candidate and the corresponding information into an excessive deletion file under a decision that an excessive deletion has been made if the corresponding information corresponding to the shortage candidate is present in the downstream addition/deletion document; adding the corresponding information to the downstream document, and deleting the corresponding information from the downstream addition/deletion document, searching a repository for the corresponding information corresponding to the shortage candidate if the corresponding information is not present in the downstream addition/deletion document, said repository being resources of information; adding the corresponding information to the downstream document, and storing the shortage candidate and the corresponding information to an addition file, if the corresponding information is present in the repository, and if the addition of the corresponding information is decided to be reasonable; storing the shortage candidate and the corresponding information into a non-addition file without adding the corresponding information to the downstream document, if the corresponding information is present in the repository, and the addition of the corresponding information is decided to be unreasonable; storing the shortage candidate into an downstream shortage candidate file without adding the corresponding information to the downstream document, if the corresponding information is absent in the repository; selecting an excessive candidate from an downstream document under excess decision rules used as a reference to decide whether some kinds of information are excessive or not, after no more shortage candidate is found in the downstream document under shortage decision rules; searching an downstream addition/deletion document for corresponding information corresponding to the excessive candidate, said downstream addition/deletion document storing information which is present in the downstream document and is absent in the downstream document; repeating the steps of selecting and searching until no more excessive candidate is found in said downstream document; storing the excessive candidate and the corresponding information into an excessive addition file under a decision that an excessive addition has been made, if the corresponding information corresponding to the excessive candidate is present in the downstream addition/deletion document; deleting the excessive candidate from the downstream document, and deleting the corresponding information from the downstream addition/deletion document after storing the excessive addition; deleting the excessive candidate from the downstream document and storing the excessive candidate into a deletion file, if the corresponding information corresponding to the excessive candidate is absent in the downstream addition/deletion document, and if the deletion of the excessive candidate is decided to be reasonable; storing the excessive candidate into a non-deletion file without deleting the excessive candidate from the downstream document, if the corresponding information corresponding to the excessive document is absent in the downstream addition/deletion document, and the deletion of the excessive candidate is decided to be unreasonable; outputting the downstream document and the downstream addition/deletion document contrastively in order to clarity the addition and deletion portions before and after refinement; deciding whether a query about a product relates to upstream information or downstream information; searching an upstream document, upstream addition/deletion document, upstream repository, downstream document, downstream addition/deletion document, and downstream repository, for an answering candidate, in accordance with results of the step of deciding until non-searched portion remains; presenting the answering candidate if it is found; storing an unsatisfied answering candidate, or a fact that no answering candidate is found, into a non-answering file; deciding information value of information associated with the upstream under upstream file elimination decision rules, said information associated with the upstream being stored in the deletion file, non-deletion file, addition file, non-addition file, special candidate file, document shortage file, excessive deletion file, excessive addition file, and non-answering file; extracting valuable information as a processing candidate; comparing the processing candidate with technical information as past results, until the last processing candidate; and storing the processing candidate into the repository in accordance with results of comparison.
37. The two-level document processing method as claimed in claim 32, further comprising the steps of: deciding whether or not the processing candidate is eligible for future repository under producibility decision rules; and storing the processing candidate into the future repository as another expression if the processing candidate satisfies the rules.