This part of IEC 62656 specifies the logical structure for a set of spreadsheets, used as “data parcels”, to define, transfer and register product ontologies. Such ontology descriptions in other literatures or disciplines are sometimes called “reference dictionaries”. Thus the logical data structure described in this standard is named “Parcellized Ontology Model” or “POM” for short, and each vehicle of transport of the model is called a “parcel”, and may be used for definition, transfer, and registering of a reference dictionary as a collection of metadata, or for similar purposes for instances belonging to a certain class of the reference dictionary. Moreover, this ontology model allows for modelling or modifying an ontology model per se as a set of instance data, thus it enables an ontology model to evolve over time. This part of IEC 62656 also includes a standard mapping between the meta-data of dictionary parcels in the spreadsheet format conforming to this standard and the meta-data represented in IEC 61360-2 compliant EXPRESS model for dictionary exchange. It is assumed that a tool supporting this part of IEC 62656 may read and write a set of spreadsheet data whose semantics and syntax are defined in this part of standard, where the physical file structure of the spreadsheets may be based on the CSV (Comma Separated Values) format, typically used in a commercial spreadsheet application, or any other tabular formats including XML schema compatible or convertible to the CSV format. The spreadsheet interface structure defined in this part of IEC 62656 contains the following: – Definition and specification of the logical structure and layout of the spreadsheet interface for definition, transfer, and registering of a reference dictionary; – Definition and specification of library instance data belonging to a class of a reference dictionary described by a set of spreadsheets conformant to this part of IEC 62656; – Definition and specification of the meta dictionary that enables the definition and transfer of a reference dictionary as a set of instance data conforming to the meta dictionary; – Definition and specification of the meta-model as data that enables the definition and transfer of a reference dictionary as a set of instance data conforming to the meta-metadictionary – Specification of the mapping between the dictionary data expressed in the spreadsheet format and the EXPRESS model specified by IEC 61360-2/ISO 13584-42 (with some elements of ISO 13584-25); – Description of the basic semantic mapping between the dictionary data expressed in the spreadsheet formats defined in this part of IEC 62656 and that of DIN 4002. The following items are outside the scope of this part of IEC 62656: – Explanation of the CSV format per se, used in spreadsheet applications; – Presentation of the data parcels conformant to this part of IEC 62656, such as colouring and sizing of the spreadsheets; – Specification of the dictionary EXPRESS model conformant to IEC 61360 or ISO 13584 series of standards; – Normative definition of the mappings between an IEC 61360-ISO 13584 compliant dictionary and another that is based upon a standard other than IEC 61360-ISO 13584; – Specification of the maintenance procedure of this part of IEC 62656. This standard is closely related with ISO 13584-35, and developed as a superset or generalisation of the latter. A major difference with the ISO 13584-35 is that this IEC standard enables updates and evolutions in a meta dictionary consisting of meta classes, by which the changes and evolution of an ontology model is realised as an update and modification of the meta dictionary, just by updates and modifications of the instances of the meta-meta dictionary. With this capability, mapping and interfacing with other ontology standards are also facilitated.