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VERS STORY | STANDARD | ASSESSMENT | PROJECTS | DIGITAL ARCHIVE | TRAINING | TOOLKIT | PUBLICATIONS | |
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2.0 VERS Metadata and NAA Metadata The VERS Metadata Scheme includes all of the National Archives of Australia (NAA) Recordkeeping metadata. This decision was made in the development of the VERS Metadata Scheme, as it was felt that the NAA metadata set provides a good description of electronic records which is suitable for short to medium term preservation, and that the Australian marketplace is too small for competing standards. Adopting the NAA Recordkeeping metadata did, however, cause some problems because of the different goals and conceptual models of the two standards. The goal of the NAA Recordkeeping metadata is to define a minimum set of metadata that all recordkeeping systems will be able to store, whereas the goal of the VERS Metadata Scheme is to represent the information required to preserve records over a long period. There is a lot of information kept in a recordkeeping system, and hence in the NAA metadata set, that is not necessary for long term preservation. Consequently some of the NAA metadata elements which appear in the VERS Metadata Standard are not critical for long term preservation and may not be widely used, or are even recommended against. Those elements which have been recommended against have been retained in order to maintain compatibility with the NAA Recordkeeping metadata. Some of the notable differences in the VERS and NAA conceptual models are as follows. A VERS record contains one or more documents, each of which may be stored as one or more encodings (physical file formats). An NAA record, however, may only contain one document which has only one encoding. The VERS format metadata thus needs to be more complex than the NAA standard in order to describe this more complex record structure. The approach to record preservation in the two models differs. The NAA recommends that records be preserved by migrating them from each system to its replacement. For this reason, the NAA Recordkeeping metadata set maintains a number of types of "history" metadata – for example, Use History (M71) and Preservation History (M76), which are continually added to over time. The VERS approach, however, is to fix records at (or close to) the time of creation using digital signatures. Although the VERS approach has many advantages over migration, it has one significant disadvantage; metadata that changes or accretes (e.g. use histories) over time is not well supported. Although it is possible to ‘layer’ metadata to support changing or accreting metadata, this is not efficient for elements that are continually modified. If a public office wishes to keep extensive metadata for VERS records that changes often over time, we recommended the following implementation model. The Record Keeping System collects and manages particularly volatile metadata (e.g. the access history or the preservation history) separately from the VERS record itself. When the VERS record is exported, this external metadata is wrapped around the original VERS record to form a new VERS record (an ‘onion’ record – see Specification 3 for further information on this process). Apart from minimising the overhead of continually forming new records, this approach allows the external metadata to be checked, and perhaps cleaned up before preserving it permanently. The one disadvantage with this approach is that the VERS record no longer stands alone for the period in which it is managed in that particular Record Keeping System; the metadata is split between the VERS metadata and the external metadata. Each part must be managed separately, and for the record to be complete, both parts must be reliable. It should be noted that a standard PROV VEO can be made compliant with the NAA’s record keeping metadata requirements by the removal of the non-NAA metadata (identified in the detailed description of the metadata elements given in section 7.0). In addition an electronic record which possesses appropriate NAA metadata can be made VERS compliant with the addition of the VERS metadata and encapsulation into the VERS long term record format (a VEO). A VEO also contains metadata not included in the NAA metadata. This metadata comprises the metadata that documents the physical representation of a VERS record, and a small amount of descriptive metadata not included in the NAA metadata. The structure of a VERS record, and its relationship with the NAA metadata, is shown in Figures 2-5. | |||||
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