There are many situations in which a set of content, such as Word and Excel documents, PowerPoint presentations, and images are all interrelated. In previous iterations of SharePoint, as well as other ECM systems, these items would be treated as separate identities. Managing these items would be on an individual basis, even if they were organized in a folder. In this scenario, if you wanted to enact a workflow across the documents it would require each item having the workflow placed on it, rather than the sum of content being treated as one set and managed appropriately.
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