The document provides an overview of PRESSOO, a methodology for expressing ISSN data elements using FRBRoo and CIDOC CRM classes and properties. It describes the 7 meetings held in January-March 2013 to examine ISSN semantics and determine if they could be expressed in FRBRoo and CIDOC CRM. PRESSOO is defined as the sum of specific classes and properties declared through this process. The document then outlines some of PRESSOO's classes and properties for describing relationships between serial works, issuance rules, transformations, and other conceptual aspects of serial publications.