Use of interoperability specifications such as standards and their implementation guides is currently hindered by lack of systematic directories. It is difficult for potential users of standards to locate potential specifications which could be useful for their specific development needs. We introduce a multi-directory interface map approach which supports systematic description of healthcare interoperability specifications through consistent metadata and complementary classifications. The approach is built on basic premises of standards portfolios in enterprise architectures as well as activity-driven and interoperability paradigm-based classifications. We illustrate the approach through a case project in Finland.