dArceo is a system for long-term preservation of source data that are logically organised into digital objects. One of the key aspects of dArceo is an OAIS-compliant migration capability. This approach has been selected due to the nature of the digital resources held by Polish scientific and cultural heritage institutions, where in most cases they handle textual, graphical and audiovisual content.

The key aim in the context of dArceo is to deliver professional tool that will assure access to the source data in a long-term perspective. This need to be done despite the changes that occur in the context of ongoing digitization practices e.g. changes of used file formats, changes in software and hardware.

dArceo was deployed for the first time in 2011 in the Digital Repository of Scientific Institutes (http://rcin.org.pl/). It covers 16 scientific institutes that cooperate and publish online and archive results of their scientific work.

Currently dArceo is used by several dozens of institutions in Poland. dArceo assures safe and OAIS-compliant approach and solution to digital preservation challenges. dArceo can be integrated with PLATON-U4 services available in the Polish scientific network PIONIER.

The core functions of the dArceo cover:

• Data storage and versioning – each digital object submitted to dArceo is transformed to so called AIP (Archival Information Package), stored and versioned appropriately, so that the user has full access both to the newest version of the digital object as well as the older ones. dArceo can use various storage devices, including hard drive, disk array and SFTP servers. It can be also easily configured to store data in the PLATON-U4 archiving services deployed in the Polish nationwide PIONIER network.
• Metadata management – in order to have full information about preserved digital objects, dArceo uses (among others) METS and PREMIS formats. Metadata files contain various information, including structural metadata, technical metadata, descriptive metadata as well as administrative metadata. Morveover, metadata can be provided either by the user (along with the content) or extracted by the build-in dArceo mechanism, which uses metadata extraction tools (e.g. FITS, FFMpeg or DROID).
• OAI-PMH Repository – provides OAI-PMH interface for digital objects stored in dArceo. Two formats are supported: Dublin Core and METS.
• Data manipulation – there are three types of data manipulation services. The first one is data migration, which play significant role in terms of long-term preservation. It uses transformation approach of the OAIS model. The second type is data conversion, which provides lossy conversion and therefore simplifies the process of building digital libraries, which primarily provide access to so called presentation versions of digital objects. The third type is advanced data delivery, which provide means to deliver source data (master files) in a personalized way, e.g. streaming/progressive download or viewing data on mobile devices.
• Data monitoring – it is possible to monitor preserved data in the context of both consistency of the data (SHA-512 checksums) and loss risk calculated based on the information gathered from the UDFR formats database.

Common space of the data manipulation functions – one of the innovative ideas in dArceo – this function allows various dArceo deployments to share their data manipulation functions. It means that one institution can provide to the other particular migration, conversion or advanced delivery function. Such an approach facilitates the cooperation between digitisation projects and provides means to foster implementation of long-term preservation activities across various institutions. Ideally, institutions with enough technical potential will provide services, that other, e.g. smaller institutions, can benefit from.

dArceo is a complex solution for data preservation, which is developed in line with well-known OAIS model. It provides many important functions that enable professional digital preservation. It also provides innovative solutions in scope of archiving and preservation, in particular common space of the data manipulation functions or advanced delivery functions.