Extensions

Extensions

Muninn is a generic archiving framework. To be able to use it to archive specific (types of) products, it is necessary to install one or more extensions.

A muninn extension is a Python module or package that implements the muninn extension interface. Muninn defines four main types of extensions: namespace extensions (that contain namespace definitions), product type extensions (that contain product type plug-ins), hook extensions (allowing functions to be executed at certain times, e.g. product creation/removal), and remote backend extensions (to support custom URL protocols for downloads performed by muninn).

A namespace is a named set of product properties (see Namespaces). Muninn defines a namespace called core that contains a small set of properties that muninn needs to archive a product. For example, it contains the name of the product, its hash, UUID, and archive date. The core namespace also contains several optional common properties for spatiotemporal data such as time stamps and geolocation footprint.

Namespace extensions contain additional namespace definitions to allow storage of other product properties of interest. For example, an extension for archiving satellite products could define a namespace that contains properties such as satellite instrument, measurement mode, orbit number, file version, and so on. An extension for archiving music could define a namespace that contains properties such as artist, genre, duration, and so forth.

A product type plug-in is an instance of a class that implements the muninn product type plug-in interface. The main responsibility of a product type plug- in is to extract product properties and tags from products of its supported product type(s). At the minimum, this involves extracting all the required properties defined in the “core” namespace. Without this information, muninn cannot archive the product.

Product type plug-ins can also be used to tailor certain aspects of muninn. For example, the plug-in controls what happens to a product (of the type it supports) when all of the products it is linked to (see Links) have been removed from the archive.

A fourth type of extension is the remote backend extension. This type of extension is specifically for muninn-pull and can introduce support for retrieving data using protocols other than the built-in support that muninn already has for http/https/ftp/file.

For details concerning the actual implementation of extensions see here.