The DOI has become essential in the scientific landscape for data citation and preservation. DOI are designed with open data requirements: they are fully integrated in the web architecture, they provide a canvas of documented resources that can be linked by cross references. The key to success is the DOI meta-data description and its documentation that improves the data visibility and citation. In this context, members of the Data Curation and Preservation (DCP) Interest Group of the International Virtual Observatory Alliance (IVOA) have worked together to identify the state of the art of different aspects of the DOI in operation in astronomy. The state of the art, shows different aspects for several types of data in the landscape - for example, the VizieR catalogue service of the Strasbourg astronomical Data Center (CDS) provides DOI for catalogues (tables and associated data). We will highlight the status of the IVOA note, and give some feedback from the experience of implementing DOI in VizieR.