Document comparison

Prior to personal computers, document comparison entailed the printing of two versions of a single document and reviewing those hard copies in detail for changes and version amendment. Included in this process were the potential for human error and the expansive administrative time necessitated by this arduous process. A ruler was used with a red pen to draw strike-through lines of deleted text and double-underline inserted text. The term "redline" came from using a red pen on the original/current version. When the document was placed in a copy machine, the copies came out black, thus the term "blackline." [1]

With the advent of personal computers and the ubiquity of word processing software, the need arose to find a way to manage changes made to document versions shared via disk, and later email. The importance of mitigating risks associated with potential document changes became essential as the amount of document and revision sharing increased. The early, first-generation document comparison software solutions provided robust document review, checking all the text in two documents for changes, and then presenting those changes in a third redline/comparison version.

As documents changed and evolved, so did document comparison solutions. The second generation of documents began utilizing tables to manage a multiplicity of document layouts. Many document comparison solutions had difficulty comparing tables in document versions. These solutions first converted tables to text arrays and then compared the created arrays. In many cases, not enough due diligence on the software’s part was conducted; users would not be informed of sections that were not successfully compared. In the second generation, Microsoft’s Track Changes option was also introduced. With Track Changes, all changes made to documents were captured and stored inside the document. Flaws in the functionality of Track Changes could render the documents unusable and some comparison offerings again had difficulty managing the complex process of comparing in a Track Changes environment.

Before third generation technology, it was common for organizations to be required to use multiple documents for one product. A main document with various supporting documents would be used to present and share necessary information. However, the third generation of documents (especially Microsoft Word) enabled multiple types of information to be presented in a single document. Compound documents could include text, tables, and various styles, and could also include a range of embedded objects, such as Excel, Visio, ChemDraw, and SmartDraw objects, and inserted images in a range of types (including jpg, tiff, bmp, and gif). While this enhancement greatly increased the usefulness of documents, it added an entirely new layer of risk to organizations that needed to fully understand changes made to document versions. The majority of document comparison software programs have not yet included mechanisms to mitigate the risk related to changes inside of embedded objects. The software program that can compare changes made in embedded objects provides pixel-to-pixel comparison of images and cell-level comparison of embedded Excel spreadsheets and other changes made to these complex, compound documents.

Lawyers and legal professionals regularly share documents with opposing counsel. As the documents constructed in this business vertical may be binding on either side's clients, it is essential that the risks associated with changes are completely mitigated. If opposing counsel makes a change that is not detected by the lawyer, such a change could negatively affect the lawyer's client and the lawyer could be liable for the damages.

Professionals in the banking, finance and accounting industries manage large amounts of data in spreadsheets. As one change to a value or formula could affect a substantial amount of data, these professionals find document comparison (such as comparison of two versions of a MS Excel spreadsheet) to be extremely useful in assuring accuracy in document change management.

Professionals in these industries regularly work with multiple versions of single documents. Document comparison software helps these professionals ensure that all changes have been acceptably integrated into latest versions and provides them with a speedy understanding of changes made in editing and versioning of the documents they work with.