KiWi is a framework for semantic social software applications that combines the Wiki philosophy with Semantic Web technologies. Applications based on KiWi can therefore leverage i.a. reasoning and versioning to follow both aspects and even go beyond existing technologies. For example, KiWi allows composition of content items, which poses a challenge to the versioning system. In this paper we discuss versioning of composed content items and challenges related to reasoning in collaborative social software, as both topics are concerned with updates on the application state. Versioning of composed content items. Versioning is an essential feature of Wikis. Currently, it is applied for a transactional unit of work in KiWi, which means that data is collected during one application transaction. Thus, one version affects only one content item. Changes during one application transaction in textual/media content, or in meta-data (e.g. applied tags and RDF triples) are stored in one version. Composed content items can either be created by copying or by referencing a content item into another one. If we apply a copy, the nested content item would be independent of the original document. A reference, however, could ensure that composed content items are kept consistent. This would lead to a reorganization of the versioning implementation. If one content item is referenced in another content item, both are placed in a new version if one of them changes. Hence, updates and versions have to be applied in a user unit of work, which means that not only updates during one application transaction are stored, but also referencing content items. This ensures the global consistency of dependent content and makes revisions more applicable for the user, who does not have to update each composed content item manually. Furthermore, the system could inform the author about dependent updates. The user could decide, whether it is reasonable to keep the reference to composed content items or to change it to a copy, so that it gets decoupled from dependency updates. ? The research leading to these results is part of the project “KiWi Knowledge in a Wiki” (http://www.kiwi-project.eu) and has received funding from the European Community’s Seventh Framework Programme (FP7/2007-2013) under grant agreement No. 211932. 3 An entity that holds content and content-related data.