, the National Aggregator of Digital Cultural Content

About is the national portal for the aggregation of digital cultural heritage and contemporary artistic production of the country. Development of the infrastructure began in 2012 with in-house expertise from the National Documentation Centre (EKT).

The purpose of is to provide a single point of access not only to all the country’s digital cultural heritage but also modern and contemporary cultural production, and to makeit open, interoperable, reusable and available long-term for individual communities of interest, such as the educational and research community as well as the general public, for learning, creativity, inspiration and innovation, thus contributing to the creation of a Digital Public Space for Culture .

At the same time, through infrastructure, the National Documentation Centre is the accredited national aggregator for the European digital platform Europeana, with which it shares the collections it collects, following international standards and specifications and ensuring the promotion of the country’s cultural heritage internationally.

Collections and institutions

The collections of items that the user can locate in correspond to the whole range and variety of the different eras of the history of the wider Greek area and the different cultures that flourished in it, from prehistoric times to the present day. The content consists, among other things, of two- and three-dimensional depictions of archaeological monuments, historical documents and manuscripts, folklore items and relics, works of fine arts, works of religious art, cartographic material, audiovisual material of the country’s intangible cultural heritage and books

Participating in are large and small cultural institutions such as museums, archives, ephorates of antiquities, municipalities, cultural institutions, galleries, research centres and libraries from all over Greece, such as the Directorate of the National Archive of Monuments of the Ministry of Culture and Sports, the National Gallery, the Greek Literary Historical Archive, the Eleftherios Venizelos Research Foundation in Chania, the Thessaloniki International Film Festival, the Peloponnesian Folklore Foundation, the Greek National Opera, etc.

The infrastructure collects and indexes metadata and preview images of digital items hosted in the individual repositories of the cultural institutions responsible for making them available. Metadata is the descriptive information that accompanies an item, such as who created it, when, where, what the subject is, etc., information that identifies an item and serves to search and retrieve it. In this way, the user can search the portal and locate the items of interest from many different institutions.

In addition to the descriptive metadata and preview images, the item pages display a standardised license designated by the institution, according to which the digital item can be used, as well as the hyperlink to the corresponding page on the institution's website. By following it, the user has access to more information in the digital environment of the institution and also can view or download the high quality primary file that the institution has. A further purpose of is to lead the user to the digital environment of the institution, increasing the visibility and traffic of its content.

Search and navigation capabilities in the National Aggregator

In addition to simple search, the portal offers very advanced and targeted search and navigation capabilities for the hundreds of thousands of items included in it. The user can, e.g., navigate based on persons , subjects , types of items, historical periods and places referred to in the documentation. At the same time, these entities are also used as filters in advanced search and the user can use them in combination, to search, for example, "letter’ (item type), "Eleftherios Venizelos’ (person), "1920-1930’ (date range) and retrieve the relevant results.

These are the most advanced search and navigation capabilities offered by an aggregator of cultural content in Europe, making a leading aggregator for European data.

Using these multiple search criteria, the team develops and curates thematic exhibitions consisting of smaller or larger sets of items that, having a conceptual relevance, tell a story. The thematic exhibitions highlight the breadth and variety of historical, artistic, archaeological, social and scientific topics that can be searched for in

Tag clouds, timeline and map display are added to the multiple ways to access items, and in the future, these capabilities will increase.

In addition to making digital items discoverable in multiple ways, aims to facilitate the further reuse of digital items in educational, research, artistic, tourism and, more broadly, creative applications. In line with the Europeana Licensing Framework, each item page displays the standardised licence designated by the institution according to which the user may use each digital item. The licence allows the user to use the digital file that can be located in the institution's repository without having to clear it each time, that is, to request the permission of the entity for its use, within the limits set by the institution. For this purpose, one of the standard machine-readable licenses Creative Commons and RightsStatements is used. Depending on the license, e.g. any use other than commercial (Creative Commons - Attribution - Non-Commercial Use) or derivative works (Creative Commons - Attribution - Non-Derivative Works) may be prohibited. In the event that a user is interested in making different uses other than those specified by the entity, the relevant rights must be cleared with the institution. Please note - permission in this case is not requested through but through the entity making the item available.

The majority of the material hosted in has been created with public funding, such as through NSRF projects, so a special effort is made to make the produced digital material open access and available under open Creative Commons licences that allow the reuse of the material from different communities of interest, with minimum restrictions in order to enhance creativity and produce new knowledge through making the most of the country’s cultural heritage.

The added value of

Content availability specifications

In order to make their collections available to, all institutions participating in must jointly adopt the Basic interoperability standards for the inclusion of collections in the National Aggregator of Digital Cultural Resources issued by EKT. These specifications are recommended for use in conjunction with the detailed Interoperability and Content Quality Specifications for publishing online digital cultural content which contains more detailed specifications and good practices for standardised online delivery of digital content, covering a broader range of topics

EKT, in accordance with its institutional role of "collecting, aggregating, organising, documenting, disseminating within and outside the country and digitally preserving scientific, technological and cultural information, content and data produced in Greece’, and, as an accredited national aggregator, is responsible for establishing and disseminating uo-to-datestandards for digitisation, documentation and interoperability of digital cultural resources.

The specifications published and updated by EKT staff encapsulate the international experience, standards and good practices that institutions’ content distribution systems, metadata and digital files must adopt to ensure the technical, semantic and legal interoperability between digital cultural collection publishing systems, the national aggregator and third-party applications such as Europeana. They cover issues such as interoperability models, the use of open licences, the required analysis of digital files and acceptable formats of digital files.

The adoption of EKT's Basic Interoperability Specifications makes the content standardised, open and interoperable while enhancing its’ quality. Through the adoption of common standards at national level, the aim was and is to adopt horizontally a common strategy on issues of quality, promotion and reuse of the country’s digital cultural heritage in terms of long-term sustainability of public investments in digitisation, to ensure the wide dissemination of cultural heritage online, in Greece and internationally, and the establishment of a single public digital cultural space particularly beneficial for research, education and creative reuse.

The Basic Interoperability Standards are now included as a requirement in the new calls for digitisation of the country’s cultural heritage, such as 03_EPAnEK (Digital Culture Projects), 7_EPAnEK (Digitisation of Cultural and Historical Monuments and Collections) and 05_EPANEK (Digital Preservation of the ERT Archive) the Digital Transformation Programme, 118 (Creation, Promotion and Exploitation of Digital Cultural Heritage) EPAnEK, while compliance with them has been requested by the Ministry of Culture with the Circular A.P. 115325_22/03/2021 (Specifications for the implementation of digital projects in the field of cultural heritage) from all its Services

By the end of 2023, more than 100 new digitisation projects are expected to comply with the Basic Interoperability Standards, while the collections produced - an estimated 500,000 items - are expected to be available for inclusion in, and through it in Europeana, gradually from the end of 2023, as foreseen in the above calls.

In addition to validating the compliance with the specifications and carrying out all the necessary procedures for the inclusion of content in the national aggregator and Europeana, in its role as a national aggregator, EKT provides the institutions with advisory and support services for the adoption of the specifications by conducting webinars and publishing supervisory material and with remote support, thus contributing substantially to the digital transformation of the cultural sector.

Semantic enrichments

The advanced search and navigation capabilities are based on the extensive semantic enrichments carried out by EKT staff. The metadata aggregated in show a high degree of heterogeneity. Dates, for example, may be inserted as: "first half of the 19th century’, "1800-1850’ or "early 19th century’ , equally, a person’s name "Rigas Feraios’, "Feraios Rigas’ or "Rigas Velestinlis’ which identify the same person. A place name such as Tripoli may refer to Tripoli in Arcadia or to Tripoli in Libya.

The heterogeneity of metadata and the ambiguity of information pose great challenges for an aggregator of large amounts of data, and if left unaddressed, the results of a search can include many failures or redundant information.

To address these challenges, in the context of modern approaches to information science, the team has over time developed a series of bilingual, mostly hierarchical, semantic vocabularies based on which systematic semantic enrichments are carried out on all the items aggregated in For their creation, existing widespread semantic vocabularies were used as a basis (Getty Art and Architecture Thesaurus, UNESCO Thesaurus, Geonames, Virtual International Authority File etc.), which were translated and expanded to meet more specific content needs of Their interconnection enables enrichment with multilingual information and improves the validity of information.

The vocabularies are represented by Linked Data technologies. In other words, each term is identified by a unique URI and can be described by relationships that allow interconnections between different terms, allowing logical reasoning to be inferred by humans and machines. For example, defining the entity "Rigas Feraios’ as being the same as the entity "Rigas Velestinlis’ means that when items about Rigas Feraios are searched for, the user wants to see items concerning Rigas Velestinlis as well.

The vocabularies are developed and hosted in the innovative infrastructure also developed by EKT staff, which has smart tools that support the mass semi-automatic enrichment of metadata. Through these tools, values from the institutions' metadata fields are mapped to EKT's target vocabularies and the whole process is supervised and approved by content curators, which ensures high quality in the produced result

Enrichments do not affect the primary documentation of the data but appear separately on the items tab. The result of the enrichment process is the addition of the new fields "EKT type", "EKT subject", "EKT person (creator/referred)", "EKT Historical period" and "EKT Place" with the new values from the EKT vocabularies. These fields answer the questions: "Who" (Vocabulary Persons of Greek History and Art), "When" (Vocabulary of Time Periods and methodology of normalisation of dates), "Where" (Vocabulary of geographical place names Geonames / Complementary vocabulary of Geoname places ), "What does it refer to" (UNESCO thesaurus - EKT edition /vocabulary of thematic labels) and "What is it" (Vocabulary "types of cultural items’).

Semantic enrichments by EKT

Enrichments improve the quality and validity of data, add a layer of multilingualism to search, allow clarification of concepts and persons, support the conceptual interconnection between items found in many different repositories and are used in advanced search. Highlighting often unexpected correlations between people, places, themes, historical periods and types of content opens new horizons for understanding and researching Greek culture.

This model systematic curation process at European level brings added value to aggregation and supports the development of advanced possibilities for searching and navigating the heterogeneous richness of the country’s cultural heritage.

The vocabularies, controlled, standardised, dynamic, extensible and open, constitute particularly valuable resources that can be used by institutions in primary documentation, enhancing the quality, interconnectivity, integration and multilinguality of the original metadata. The reuse of such resources, which is also part of the strategic objectives of the Ministry of Digital Governance in the context of Open Data policies, improves accessibility to cultural heritage at national level and achieves economies of scale in documentation processes.

For more information on semantic enrichments please click here here.

Participation in Europeana and promotion of Greek content internationally

Since 2018, the National Documentation Centre has been the accredited national aggregator for the European platform Europeana, with which it has shared more than 560,000 items, ensuring the promotion of Greek content internationally.

The increase in Greek content available in Europeana is also one of the most central national objectives in the field of Culture in the context of the Digital Bible developed by the Ministry of Digital Governance, which supervises EKT (9.5.2. Works, "Making cultural content available in Europeana's digital library’)

The policies and specifications for inclusion of collections in are fully compatible with those of the European Publishing Framework and Europeana Licensing Framework. This means that the sharing of the institutions' collections with Europeana is streamlined, thus, removing any additional procedure for the institution and without any financial burden for it

In the context of its role as a national aggregator for Greek cultural content, the members of's development team represent EKT by participating in Europeana’s Aggregator Forum in order to exchange know-how and participate in the co-shaping of European developments related to the Recommendation for a Digital Space for Culture. In addition, members participate in working groups such as the Data Quality Committee that studies evolving standards for optimising the availability of metadata and the Aggregator User Group, in which they check and give feedback on the new functionalities of the Europeana portal, the way Greek content is presented on it, etc.

Finally, EKT has participated in European cooperation projects for the distribution of content in Europeana such as Europeana Common Culture and the Crafted project.

Technological Infrastructure

EKT has developed a modern modular infrastructure addressing the entire life cycle of content aggregation, covering harvesting, validation and semantic enrichment of cultural data, publishing,and secure storage of digital resources and their publication in Europeana

The aggregator is a component of a larger infrastructure consisting of 6 disparate systems: the Digital Content Harvester System, the Validator Compliance Control System, the Linked Open Data publishing system, the Aggregator Platform, the public web portal and the Preservator Long-term Content Storage System.

The Harvester system collects metadata and digital files through the OAI-PMH protocol, stores them and makes them available upon request from a user or from an external system through its graphical web user interface or web services (RESTful API), respectively. The collected content is stored and can be reused by third-party systems such as those of the infrastructure. The Harvester system also has a service to convert the digital files it collects into preview images

The Validator system is the information system that checks repositories for the extent to which they comply with quality and interoperability specifications. is an information system where authorised institutions register, develop and interconnect vocabularies and thesauri of terms. At the same time, it has an state-of-the-art tool for mass semi-automatic semantic enrichment and homogenisation of content that can be used by both repositories and aggregators. EKT uses this tool to enrich the content aggregated in in order to optimise search and navigation services.

The Aggregation Platform is the backend of It has an administrative environment for the registration of institutions and collections, the definition of technical parameters that designate how each collection is imported, such as the transformation, cleaning and semantic enrichment actions to be applied, the initiation and monitoring of metadata and preview file import processes and the configuration of the public portal. The metadata are transformed by supported schemas (ESE, EDM, OAI_DC+METS, QDC+METS, LIDO) into an internal implementation of the EDM (Europeana Data Model), Europeana's cultural data sharing model.

The public Portal is a public web environment that provides end-users with centralised access to collections through multiple search engines, filtering, navigation and visual presentation. At the same time, it publishes metadata as Linked Data in RDF format and through APIs.

Finally, the Preservator system underpins the safe storage of a copy of the digital files. This service was made available for the repositories of the beneficiaries of calls 31 and 31.2 and will be used again in the context of the new calls.

The infrastructure and the individual systems were designed and developed entirely by EKT. They were developed in the Java programming language and specifically with the Spring programming framework. Relational and non-relational databases (ProstgeSQL and Mongo DB) are used as an indexing and search system while Apache Sorl. Communication between systems is carried out with RESTful APIs. For the front-end of Bootstrap is used in conjunction with JQuery and a number of external libraries, such as highcharts.js (for timeline), jqcloud.js (for tag clouds), select2 (for dynamic checklists) and leaflet.js in conjunction with maps (for navigation and presentation of documents on a map).

Development History

Development of begun in 2012 by the National Documentation Centre (EKT) in collaboration with the OP "Digital Convergence’ with the aim of gathering and consolidating the entire Greek Digital Cultural Heritage produced by entities with public funding initially under Calls 31 "Culture’ and 31.2 "Digital Services for the Promotion of the Greek Digital Cultural Reserve’.

The first phase of development of was included in the project "Platform for the Provision of Services for the Deposit, Management and Dissemination of Open Data and Digital Content’ implemented by EKT under the OP "Digital Convergence’ (NSRF), co-financed by Greece and the European Union - European Regional Development Fund, and was completed in early 2015

Within the framework of that programming period, EKT defined the relevant digitisation and documentation specifications utilising its know-how in the field, the international environment and standards in the respective regions and developed the following three services: the Content Quality Control and Interoperability Compliance Service (Validator), the Unified Catalogue and the Digital Long term Storage service (Preservator). Institutions created repository systems for the diffusion of the produced material. EKT collected the content, validated and certified its quality for compliance with the specifications with the Validator system, semantically enriched it, published it in the aggregator, stored it in the Preservator system under safe storage conditions and, finally, gradually made the metadata available to the European Digital Library Europeana. was first published in 2015, bringing together the collections of the above works, a total of 42 Projects, while in 2016 it began to share material with Europeana.

Subsequently, the team continued to enrich the portal with new collections from reputable institutions in the country and to upgrade it with value-added functions.

The systematic editing of the data began in 2016 when the semantic vocabularies and the semantic enrichment infrastructure began to be developed. First the vocabulary of document types was developed, and then the mechanism for normalising dates and enrichments with historical periods was developed in 2017. Next, the vocabulary of UNESCO topics was developed and a separate complementary vocabulary with thematic terms was developed, while the relevant enrichments were completed in 2019. This was followed by the development of the vocabulary of the persons and the related enrichments were completed in 2022, while the most recent cycle of retrospective enrichments on all items was completed in 2023 with the enrichments in terms of geospatial data. The completion of retrospective semantic enrichments in each new field led to the development of new mechanisms for searching and navigating the content.

In 2018, the National Documentation Centre was accredited as a national aggregator of cultural data through the infrastructure for the European digital library Europeana. In this role, EKT is represented in the Forum of Europeana National and Thematic Aggregators and participated in the European project "Europeana Common Culture’, which was completed in December 2020, increasing by approximately 300,000 the Greek items that can be found on the European platform and significantly improving the quality and visibility of Greek cultural content internationally. The project aimed, among other things, to strengthen the role of national cultural content aggregators, to exchange know-how between them, to harmonise policies, technologies and infrastructures and to disseminate their work and that of Europeana as a whole.

In 2020, the upgrading and expansion of began within the framework of the project "National Research and Technology Information System: Infrastructure for the Aggregation, Documentation and Dissemination of Digital Content ensuring interoperability, long-term preservation and open access’ (Operational Programme "Public Sector Refor’, NSRF). The Project started in April 2020 and ends in July 2023 and aims, among other things, to enhance the interoperability and quality of digital content produced in the country - with emphasis on new digitisation projects, the scaling up of digital content aggregation and its central dissemination through and the technological upgrade of EKT's aggregation infrastructure and portal with emphasis on its semantic interconnected content and the development of new innovative ways of searching for it

In the context of this project, which coincided to a large extent with the Covid pandemic, emphasis was placed on the development of semantic enrichment infrastructure and processes, carrying out massive retrospective enrichments of all content and the development of advanced search and navigation functions based on them, such as the design of search mechanisms for persons and thematic exhibitions, all of which attracted a critical number of new data providers, who, being closed to the public, were looking for new ways to communicate online with their audience. At the same time, the lockdown boosted the extroversion of, through a large number of highly successful webinars that attracted a great number of different communities of interest. Thanks to them, within the framework of the current project, the content has doubled and the traffic of the Portal has quadrupled.

In 2020, EKT published a new detailed guide to good practices for organisations wishing to publish interoperable, open and quality cultural content online, as well as a new, simplified set of specifications for the inclusion of collections, with the aim of making it as simple as possible for all organisations to adopt them

In 2022, compliance with the Basic Interoperability Standards was incorporated as a requirement in new calls for proposals that fund the digitisation of the country’s cultural heritage (Call 03_EPAnEK Digital Transformation and 118 of EPANEK, among others). This development is expected to significantly scale up the availability of the country’s cultural heritage online in a standardized way, which contributes significantly to ensuring sustainability in digitalisation investments. can be said to be going through a period of maturity, having developed infrastructures and processes that allow the aggregation and semantic enrichment of the country’s cultural heritage, in a model way, for European standards, and is facing the challenges of the next phase of development, mainly the escalation of aggregation, which in turn requires not only the cultivation of the digital skills of the actors and the communities of interest involved in the context of their digital transformation, but also the redesign of infrastructure and engagement processes to allow increased participation, collaboration, transparency and control to achieve the Digital Public Space for Culture

The team

The core team of consists of:

Dr. Haris Georgiadis , Scientific Lead and Principal Developer

Georgia Aggelaki , Network Development and Outreach

Agathi Papanoti , Data Ingestion and Semantic Enrichments

Elena Lagoudi , Digital Curation

Anastasia Gasia, Semantic enrichments

Maria Fasoi, Semantic enrichments

EKT staff members that have also contributed in the current phase of development: Dimitra Pelekanou/Margarita Skandali (Graphic Design), Nikos Vassilogamvrakis/Alexia Panagopoulou (Semantic Enrichments), Dimitris Charlaftis (upgrade to new software releases), Kostas Bekos (Copy Editing)