6.1 TECHNICAL LEVELS OF INTERACTION BETWEEN OAIS ARCHIVES

In general one OAIS is not interoperable with another; however, there are a number of reasons that some level of interoperability may be desirable, motivated for example by Users, Producers or Management; even interoperable Archives may have different Designated Communities—even for the same digital objects—and hence different requirements for Representation Information and/or Descriptive Information.

OAIS associations can be categorized technically by both external and internal factors. External factors include characteristics of the Producer and Consumer communities. Internal factors could include common implementations of the information models presented in 4.2, or multi-Archive sharing of one or more of the functional areas presented in 4.1.

This subsection defines four categories of Archive association. The first three categories have successively higher degrees of interaction:

– Independent: Archives motivated by local concerns with no management or technical interaction among them.

– Cooperating: Archives with potential common producers, common submission standards, and common dissemination standards, but no common finding aids.

– Federated: Archives with both a Local Community (i.e., the original Designated Community served by the Archive) and a Global Community (i.e., an extended Designated Community) which has interests in the holdings of several OAIS Archives and has influenced those Archives to provide access to their holdings via one or more common finding aids. The Access needs of the Local Community usually have priority over those of the Global Community. Global dissemination and Ingest are optional features.

– Shared resources: Archives that have entered into agreements with other Archives to share resources, perhaps to reduce cost. This requires various standards internal to the Archive (such as ingest-storage and access-storage interface standards) but does not alter the user community’s view of the Archive.

The remainder of this subsection gives a more detailed view of these categories of association.

6.1.1 INDEPENDENT ARCHIVES

An independent Archive is assumed to serve only a single Designated Community. The Archive and the Designated Community must agree on the design of DIPs and Finding Aids. An independent Archive may choose to design these structures based on formal or de-facto standards, which would allow cooperation with other Archives that implement the same standards. However, the design decisions to use these standards are not based on the possibility of inter-operation with other Archives, but rather on local requirements and cost savings.

The classification of an Archive as independent is not based on its size or distributed functionality. An independent Archive may occupy one site, or may be physically distributed over many sites. It may use many standards for a given internal element. However, if there is no interaction with other Archives, the Archive is independent.

6.1.2 COOPERATING ARCHIVES

Cooperating Archives are based on standards agreements among two or more Archives. The simplest form of cooperation between Archives is when one Archive acts as a Consumer of material from another Archive. In this case the consuming Archive must support the DIP format of the producing Archive as a SIP format. Cooperating Archives have related communities of interest, so they order and ingest data from other cooperating Archives and possibly have common data Producers. No common access, submission or dissemination standards are assumed. The only requirement for this architecture is that the cooperating groups support at least one common SIP and DIP format for inter-Archive requests. The control mechanism for this sort of inter-operation can be Event Based Order requests at each Archive.

Figures 6-1 and 6-2 illustrate the concept of cooperating Archives.

At a rudimentary level of Archive interaction, figure 6-1 represents a simple mutual information exchange agreement between Archives.

NOTE – In this and the following figures, the OAIS is represented as a multi-port device following the arrangement of figure 6-1. In each case, a two-Archive federation is shown for simplicity, although the concept can be extended indefinitely.

The essential requirement for this federation is a set of mutual Submission Agreements, Event Based Orders, and user interface standards to allow DIPs from one Archive to be ingested as SIPs by another. Therefore, it assumes that some pair-wise compatibility has between established between the Archives. This does not necessarily require common access, dissemination and submission methods for all participants, although that might encourage more exchange. This level of agreement would also be useful when the holdings of one Archive were consolidated/transferred into another Archive because of Management issues.

Figure 6-1: Cooperating Archives with Mutual Exchange Agreement

Figure 6-2 is an example of OAIS Archives that have standardized their submission and dissemination methods for the benefit of users. No special external element is needed for this. Its disadvantage is that there is no formal mechanism for exchange of Description Information so Consumers must have separate Search Sessions to locate AIPs of interest.