## 2 Literature Review
Offered interfaces enable the integration of DRMSs with existing enterprise architectures. DRMS often run in a \begin{table}
\begin{tabular}{c c c} \hline \hline
**Project Name and Its Homepage** & **Supported Metadata Standards** & **Software Type and Search Features** \\ \hline Fedora Commons, & MODS, Dublin Core, QDC out of the box, & platform only, with API, with native \\ [[https://duraspace.org/fedora/](https://duraspace.org/fedora/)]([https://duraspace.org/fedora/](https://duraspace.org/fedora/)) & arbitrary metadata sets & Linked Data support \\ Islandora, & MODS, Dublin Core, PREMIS, & repository, built on Fedora Commons, \\ [[https://islandora.ca](https://islandora.ca)]([https://islandora.ca](https://islandora.ca)) & MARCXML & uses Apache Solr \\ Samvera (previously Hydra), & MODS, DC, DC11, EDM, FOAF, custom & bespoke solution, build on Fedora \\ [[https://samvera.org](https://samvera.org)]([https://samvera.org](https://samvera.org)) & metadata set & Commons, uses Apache Solr \\ DSpace, & Dublin Core, arbitrary metadata sets (but & repository, uses Apache Solr \\ [[http://duraspace.org/dspace/](http://duraspace.org/dspace/)]([http://duraspace.org/dspace/](http://duraspace.org/dspace/)) & flat) & repository, based on ISO-OAIS functional \\ Archivematica, & METS, PREMIS, Dublin Core, Library of & model, uses Elastic Search \\ [[https://www.archivematica.org/en](https://www.archivematica.org/en)]([https://www.archivematica.org/en](https://www.archivematica.org/en)) & EAD, Dublin Core XML, MODS XML, & repository, uses Elastic Search \\ [[https://www.accessstemmemory.org/en](https://www.accessstemmemory.org/en)]([https://www.accessstemmemory.org/en](https://www.accessstemmemory.org/en)) & EAC, SKOS & repository, uses Elastic Search \\ Invenio, & MARC & repository, uses Elastic Search \\ [[https://invenio-software.org](https://invenio-software.org)]([https://invenio-software.org](https://invenio-software.org)) & VIVO ontology, arbitrary metadata sets & repository, uses Apache Solr \\ VIO, & (custom ontologies) & repository, uses Apache Solr \\ [[https://duraspace.org/vivo/](https://duraspace.org/vivo/)]([https://duraspace.org/vivo/](https://duraspace.org/vivo/)) & EAD, DC, METS, PREMIS, and others & repository, uses Apache Solr \\ RODA, & (e.g., NISO Z39.87 for digital still images) & repository, uses Apache Solr \\ [[https://www.reda-community.org](https://www.reda-community.org)]([https://www.reda-community.org](https://www.reda-community.org)) & custom metadata set & repository, uses custom indexer \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Selected digital repositories delivered as software packages. cloud, like ContentDM ([[https://www.oclc.org/en/contentdm.html](https://www.oclc.org/en/contentdm.html)]([https://www.oclc.org/en/contentdm.html](https://www.oclc.org/en/contentdm.html))) or ResourceSpace ([[https://www.resourcespace.com](https://www.resourcespace.com)]([https://www.resourcespace.com](https://www.resourcespace.com))). The digital repository concept sometimes extends to specialized systems used to store and process files in the cloud, like DuraCloud ([[http://duraspace.org/duracloud/](http://duraspace.org/duracloud/)]([http://duraspace.org/duracloud/](http://duraspace.org/duracloud/))), OpenStack ([[https://www.openstack.org](https://www.openstack.org)]([https://www.openstack.org](https://www.openstack.org))). However, these belong to the class of webdisks, rather than to digital repositories. One might also wonder whether to assign social networking sites or commercial services, which offer media sharing, storage, and streaming functions, to the category of digital repositories. However, these portals and services have different functionality and significantly different objectives than long-term preservation and sharing of scientific resources, data conversion for better accessibility, and other aims addressed by digital repositories. Digital repositories are also close to digital libraries, which are web sites consecrated to preserve and distribute knowledge.