## 5 Discussion  
When estimating the resources required and investing in infrastructure, designers of digital repositories must anticipate all data processing scenarios and their effects. However, this estimation can sometimes be challenging. For example, in our case, it turned out that the information model identified during the preliminary analysis needs some extensions. Every processed multimedia file had to be associated with the results of this processing. The files generated for rendering purposes (images in different resolutions required by image server, thumbnails used as previews of data files, audio/video files needed for streaming), and for increasing availability of the deposited resources (transcripts, subtitles, extended subtitles for video, pdf documents with text layer resulting from running OCR tools on scans) require proper handling. It was not easy to decide whether to use existing digital repositories that were already available and used by others or to start a new implementation. The number of factors to consider included a price, a type of license, a possibility and easiness of modifying the code, the size and reliability of the community, the data and metadata model provided, offered integration paths with other software, supported authentication and authorization methods, the performance (including handling of big files and a significant number of files), enhanced search functions, a possibility and way of presentation of different types of data, semantic web functions provided and graph database support, open formats supported, Polish law requirements and recommendations for open data repositories, WCAG compliance and other accessibility aspects. An essential step for the project members was to check the reusability of infrastructure and software in terms of money and knowledge already invested. The main discovery of this stage was that there is a set of excellent software products on the market, but most of them are tailored to specific types of data or use cases, and none provides all the desired features out of the box. The biggest obstacles were a lack of possibility to implement the required data model and difficulties with software solutions extensibility. It was challenging to find an implementation that fully supports expected semantic web enablement (SPARQL endpoint, dereferencing through content negotiation, etc.). From various candidates, Vivo offered the closest metadata model to the required one. The ontology used in it contains many classes and properties relevant to the academic community. However, due to deposited resources' heterogeneity and specific presentation requirements, it had to be abandoned. The further experiments also showed that mapping a custom metadata model using schema.org vocabulary brings many benefits in resource discovery (google search engine can index published records more effectively). These were the primary reasons to start a new software project. The other reasons came from the various technical obligations (for example, caused by the need for integration with the services built in the scope of e-science.pl project). Side effects of the project are the experiences gained during implementation. This manuscript hides them in-between lines. For example, the statistics collected should help estimate the requirements for similar projects and the following recommendations developed during the project implementation might be helpful. For safety reasons, an excess of hardware and software is recommended. With correctly designed architecture it may protect from Single Point of Failure, SPoF. In solvingsimilar problems, disk arrays, redundant SAN (Storage Area Network), FC (Fibre Channel) and redundant network equipment (switches, hubs, etc.) will be useful. However, the task of infrastructure maintenance relied not only on hardware related issues. Software issues, in particular related to the dependencies arising from the security mechanisms implemented, are also important. They enforce the need to obtain and update certificates or maintain domain names.