Work in progress
by Gérald Jean Francis Banon
November 2023
Updated in October 2025
The need to preserve digital information in the long term is a primary concern of many initiatives, one of which is the development of the Reference Model for an Open Archival Information System (OAIS) by the Consultative Committee on Spatial Data Systems (CCSDS) and the International Organization for Standardization (ISO) [1].
One of the open preservation problem is how to maintain the integrity of hyperlinks in the long-term, which may extend indefinitely.
In a previous note, the existence of a digital service that turns the persistent hyperlinks independent of the URL scheme and the resolver domain name has been shown [2].
The purpose of this note is to illustrate the use of that digital service in the case of a Federation of Archives that allows persistent hyperlinks to work with local resolvers instead of a global resolver.
Inicially, it is suposed that each Archive identifies its Archival Information Packages (AIPs) independent of each other. In this way, as commented in [1], when an Archive joins a Federation, there is no assurance that some of its current AIP identifiers are not already used by other members of the Federation. A general solution to this problem is to form the AIP identifiers in the Federation by assigning a Unique Name for each Archive in the Federation and concatenating it to the identifier for each AIP preserved by that Archive.
Here, to assign a unique name to each Archive we propose a simpler alternative standard to ISO X.500 Directory Services Naming. This standard reuses part of the standard presented in [3]. Futhermore, to refer to the unique name of an Archive, we use the simpler expression "Archive Name"
Since it is assumed that each Archive acts as a local resolver for its own AIP identifiers. Therefore, instead of talking about the name of an Archive, we prefer to talk about the Resolver ID.
This HTML page contains two examples of Fully Persistent Hyperlinks (see definition below). The first uses the namespace prefix (see definition below) upn:3Q3U5H8 and the second uses upn:GJR3MH (the UPN URI scheme stands for Uniform Package Name).
This page, the source ressource, is the Data Object (Digital Object) of an AIP hosted by an Archive that is a member of a Federation of Archives of the type Distributed Finding Aid [1]. Currently, the Federation is composed of the following members identified here by there namespace prefix and URL: The first Archive (upn:E8KGRE) in this member's list is the global node of the Federation, in the sense that it resolves all the URIs pointing to any AIPs within the Federation.
The second Archive (upn:3Q3U5H8) is a local resolver in the sense that it resolves all the URIs pointing to any AIPs within the Archive itself.
Each federated member identifies its AIPs and acts simultaneously as an Archive, a proxy resolver (when acting as a source Archive, i.e. an Archive that contains the source resource) and a local resolver (upn:3Q3U5H8 and upn:35SP775) or the global node (upn:E8KGRE).
– A Namespace is a set of names.
– A Namespace Prefix is a unique name assigned to an Archive. At the time of creation of an AIP in the Archive, this name is preserved in the AIP Provenance Information and is used as a namespace prefix to be concatenated to the identifier of the AIP preserved by that Archive.
– An Identifier (of an object) is a name within a specific namespace that is assigned exclusively and forever to that object.
– A Hyperlink (from a Source Object - SO to a Destination Object - DO) is a computational command inserted into the SO, whose argument specifies the URL of the DO, and which, when activated, brings the DO on the user's screen.
– A Persistent Hyperlink (from a Source Object - SO to a Destination Object - DO) is a computational command inserted into the SO, whose argument specifies a URL scheme, a resolver domain name and the DO Identifier that is used by the resolver to find the current URL of the DO, and which, when activated, brings the DO on the user's screen.
– An Almost Fully Persistent Hyperlink (from a Source Object - SO to a Destination Object - DO) is a relative Persistent Hyperlink (from the SO to the DO). In other words, the computational command argument specifies neither the URL scheme nor the resolver domain name, but it does specify the namespace prefix (for example, upn:3Q3U5H8 or urn:doi). In the background, the DO Identifier may need be resolved by a global resolver.
– A Fully Persistent Hyperlink (from a Source Object - SO to a Destination Object - DO, the latter belonging to a Federation of Archives) is a relative Persistent Hyperlink (from the SO to the DO) whose DO Identifier is resolved by the DO Archive (i.e. the Archive that contains the DO) itself acting as a local resolver or by the global node of the DO Federation (i.e. the Federation that contains the DO), both at the request of the SO Archive (i.e. the Archive that contains the SO) acting as a proxy resolver.
Examples of three Almost Fully Persistent Hyperlinks are given in [2]. In the next section, examples of two Fully Persistent Hyperlinks are now given.The two hyperlinks below are relative Persistent Hyperlinks†. This can be verified by looking at the value of the respective href attribute in the source code of this HTML page.
They are Fully Persistent because the SO Archive acts as a proxy resolver which triggers the local resolver of the original DO Archive, if it still exists, ortherwise the global node of a Federation (if a Federation has accepted to host the original DO (i.e. in both cases, a global server does not need to be triggered).
Observation 1: The above examples work because the SO (containing this page) and the DOs of the hyperlinks have been deposited in federated Archives (Digital Repositories - Data Providers), all hosted in an experimental computational platform called URLib and thereby, parts of what is called the IBI network of Archives. Each of these Archives uses Uniform Resource Identifiers (name type URI) to identify their AIPs and operates as both a data provider and a local resolver for all the AIPs in the Federation. Since both DOs are part of the Federation, they can accessed without the held of a global resolver. These examples demonstrate that it would be advantageous for the AIPs of any Archive to be identified by name type URIs, should the Archive ever need to join a Federation.
Observation 2: It is sufficient for an Almost Fully Persistent Hyperlink (from a SO to a DO) to become a fully persistent hyperlink (from a SO to a DO) to ensure that the resolution doesn't depend on a global resolver, that is, it only depends on the resolution ability of the SO data provider itself.
Observation 3: The upn URI scheme still has to be registered with IANA. The acronym upn stands for Uniform Package Name. Inicially, this scheme was designed to identify any pecified naming system used to identify Archival Information Package, nevertheless it can be used to identify any type of naming sistem to turn a local namespace into o global one. To create and register a new UPN namespace ID point to ibi-:QABCDSTQQW/4DMTTQE and send an e-mail to urlibservice@gmail.com stating the resolver's domain name for the created UPN namespace ID.
A next note introduces yet another definition of hyperlink, the so-called robust hyperlink, which is the last stage of the proposed advanced hyperlink types and contributes to solving the problem of the continued existence of Web resources [4].