What is the implied undertaking of a party in a civil action?

The court discusses the rationale for the implied undertaking rule at paragraphs 24 and 25: 24 In the first place, pre-trial discovery is an invasion of a private right to be left alone with your thoughts and papers, however embarrassing, defamatory or scandalous. At least one side in every lawsuit is a reluctant participant. Yet a proper pre-trial discovery is essential to prevent surprise or "litigation by ambush", to encourage settlement once the facts are known, and to narrow issues even where settlement proves unachievable. Thus, rule 27(22) of the B.C. Rules of Court compels a litigant to answer all relevant questions posed on an examination for discovery. Failure to do so can result in punishment by way of imprisonment or fine pursuant to rules 56(1), 56(4) and 2(5). In some provinces, the rules of practice provide that individuals who are not even parties can be ordered to submit to examination for discovery on issues relevant to a dispute in which they may have no direct interest. It is not uncommon for plaintiff's counsel aggressively to "sue everyone in sight" not with any realistic hope of recovery but to "get discovery". Thus, for the out-of-pocket cost of issuing a statement of claim or other process, the gate is swung open to investigate the private information and perhaps highly confidential documents of the examinee in pursuit of allegations that might in the end be found to be without any merit at all. 25 The public interest in getting at the truth in a civil action outweighs the examinee's privacy interest, but the latter is nevertheless entitled to a measure of protection. The answers and documents are compelled by statute solely for the purpose of the civil action and the law thus requires that the invasion of privacy should generally be limited to the level of disclosure necessary to satisfy that purpose and that purpose alone. Although the present case involves the issue of self-incrimination of the appellant, that element is not a necessary requirement for protection. Indeed, the disclosed information need not even satisfy the legal requirements of confidentiality set out in Slavutych v. Baker (1975), 1975 CanLII 5 (SCC), [1976] 1 S.C.R. 254 (S.C.C.). The general idea, metaphorically speaking, is that whatever is disclosed in the discovery room stays in the discovery room unless eventually revealed in the courtroom or disclosed by judicial order.