Since 2020, the CDSP has experimented with DDI-Lifecycle using Colectica to build a question and variable bank. A portal has been made publicly available (https://explore.cdsp.sciences-po.fr/). Maintaining efforts to further improve this tool, we currently explore DDI-L opportunities and Colectica Designer features to ease longitudinal data management. The presentation will demonstrate the value of ontologies to drive harmonization and to improve end-users (meta-)data exploration at the variable level. First, we present how we have harmonized historical electoral surveys data on France using ddi3.2 conceptual constructs. Second, we detail the outputs and benefits of this endeavor from the end-users point of view.