The dominance of digital objects in today´s information landscape has changed the way humankind creates and exchanges information. However, it has also brought an entirely new problem: the longevity of digital objects. Due to the fast changes in technologies, digital documents have a short lifespan before they become obsolete. Digital preservation, i.e. actions to ensure longevity of digital information, thus has become a pressing challenge. Different strategies such as migration and emulation have been proposed; however, the decision between available tools for format migration is very complex. Preservation planning supports decision makers in reaching accountable decisions by evaluating potential strategies against well-defined requirements. Especially the evaluation of different migration tools for digital preservation has to rely on validating the converted objects and thus on an analysis of the logical structure and the content of documents. This paper presents the eXtensible Characterisation Languages (XCL) that support the automatic validation of document conversions and the evaluation of migration quality by hierarchically decomposing a document and representing documents from different sources in an abstract XMLlanguage. We present the context of the development of these languages and tools and describe the overall concept and features of the languages and how they can be applied to the evaluation of digital preservation solutions.