ISO/IEC 29500-2:2021 states that “Core properties enable users to get and set well-known and common sets of property metadata within packages”. The core properties are the category of the Package, the status of the content, the resource creation date, the creator, a description of the content, an identifier, a set of keywords, the language of the content, the last modifier, date and time of the last printing, modification date, revision, subject (or topic) of the content, a title, and the version. These properties can be empty or omitted. The entire Core Properties Part can be omitted if there are no core properties present.