Adding semantic annotations to archival metadata allows to generate an alternative representation of the dataset in the form of a graph. This can be useful for multiple reasons: discovery of new relationships between objects, improves findability and allows for more sophisticated queries using the sparql query language. In this poster we will explain the rationale used to develop a web-based tool to help users deal with this task using a semi-automatic approach that ensures high quality annotations while leveraging natural languages understanding techniques to speed up the process.