A new "Guideline on using SDMX Annotations" is available to improve machine interactions through a controlled vocabulary for the Type property of the SDMX Annotation construct and a recommended usage for the other properties that will greatly improve the interoperability of Annotations between SDMX-compliant organisations.  

The Annotation is a construct that contains user or organisation-specific metadata. The Annotation construct in SDMX is available to most of the SDMX structural metadata artefacts.  

The main advantage of the Annotation is its flexibility as all properties can be tailor-made and there is no limit to their number. This can prove very useful for specific applications, such as dissemination tools. The main drawback is poor interoperability as Annotations convey no semantics and are not standardised. This means that organisations that want to exchange Annotations and process them automatically must agree upon, at least, a common naming syntax.