The Cross-Domain Interoperability Framework (CDIF) is an emerging idea for a set of guidelines around domain-agnostic standards for supporting the implementation of interoperability and reusability of FAIR data, especially across domain- and institutional boundaries. The CDIF aims to provide a list of standards in a range of functional roles to support the next level of interoperability, but giving domains the “lingua franca” against which to map domain-specific standards and ontologies. Such standards as Schema.org, DCAT, SKOS, PROV-O, DDI-CDI, and I-ADOPT are being suggested. The functional roles include the description of units and measurements, the relation of variables to concepts and consistent descriptions of data structure. The work around the CDIF is based on practical use-cases, and has been slowly growing out of various activities conducted under CODATA’s Decadal Programme 'Making Data Work...' and in partnership with the DDI Alliance at a series of Dagstuhl Workshops and the development of DDI’s Cross-Domain Integration specification. It is still in early stages, but reflects an emerging consensus among many of the participants in this endeavour. WorldFAIR provides an opportunity to take this work forward and to test and refine it with the WorldFAIR case studies and on the basis of information gathered through the FIPs exercises. This collection contains preparatory, working documents used as input to workshops and meeting on the topic. The Cross-Domain Interoperability Framework: A Proposed Lingua Franca for FAIR Data Reuse (Discussion Draft), 15 August 2022, was prepared as input to the 2022 Dagstuhl Workshop. The Cross-Domain Interoperability Framework (CDIF): Current Status, 14 December 2022, summarised current thinking as input to the first meeting of the CDIF Working Group and Advisory Group, convened in support of this work under the WorldFAIR Project.