From aggregation to data space participation: assessing the readiness of European cultural heritage portals for the common European data space

The large-scale digitisation of cultural resources has been closely associated with the development and uptake of advanced digital technologies, including three-dimensional (3D) imaging, artificial intelligence (AI), machine learning, cloud computing, data analytics and virtual and augmented reality. Leveraging increasingly complex digital data and metadata, these technologies enable new forms of knowledge production, foster innovation and expand access to digital cultural heritage resources, thereby reinforcing the public value of digitisation.

In response to these developments, the European Union has progressively established a policy and funding framework supporting digitisation across its Member States, with cultural heritage identified as a strategic domain. From an early stage, European policymakers recognised that digitisation would have implications extending beyond research and education, shaping cultural tourism, creative industries and the broader digital economy.

A key milestone in this process was the establishment of Europeana in 2008 as a pan-European digital infrastructure aggregating metadata from galleries, libraries, archives and museums (GLAM). Initially conceived as a unified access point to distributed digital collections, Europeana prioritised accessibility and interoperability through shared metadata standards (Europeana, 2025). Subsequent policy instruments, notably the recommendation on the digitisation and online accessibility of cultural material and digital preservation (Commission Recommendation of 27 October 2011 on the digitisation and online accessibility of cultural material and digital preservation, 2011), further consolidated cultural digitisation as a matter of strategic public governance.

European Commission Recommendation (EU) 2021 / 1970 on a common European data space for cultural heritage (CEDSCH), laid down the data space paradigm within cultural heritage policy. This policy instrument reframed digital cultural heritage not merely as content to be accessed, but as data to be shared, reused and governed within a federated European infrastructure. The recently published Strategy on a Common European Data Space for Cultural Heritage (CEDSCH) 2025–2030 (2025) positions Europeana and its partners as the steward and operational backbone of this emerging CEDSCH.

At the same time, the transition from a discovery-oriented platform to a fully fledged data space raises substantial conceptual, technical and governance challenges. The increasing complexity of digital cultural content, combined with growing demands for data sovereignty, rights management and research-oriented reuse, exceeds the functional scope of traditional metadata aggregation models. These challenges provide the central motivation for the present study.

Digital heritage is defined by UNESCO as comprising “unique resources of human knowledge and expression” created digitally or converted from analogue sources, including texts, databases, images, audio, software and web-based materials (UNESCO, 2003). Due to their often fragile and vulnerable nature, such materials require deliberate strategies of production, management and long-term preservation.

Within this conceptual framework, digital cultural heritage data, understood as digital representations, descriptive metadata and research outputs related to heritage objects – form the foundation of the CEDSCH (Dobreva et al., 2022). In line with the Data Governance Act (European Union, 2022), data are defined broadly as any digital representation of acts, facts, or information, including audiovisual recordings and their compilations.

A data space can be understood as a federated ecosystem in which trusted participants share data in a sovereign and interoperable manner to generate value across multiple use cases (International Data Spaces Association, as cited in Dobreva et al., 2022). Applied to cultural heritage, this model implies that data spaces must support not only public access and dissemination, but also computational reuse for research, including AI- and machine-learning–based methods.

As a result, mere data availability is insufficient. Cultural heritage data must be of high quality and accompanied by rich metadata and documentation addressing provenance, ownership, licensing and reuse conditions. This requirement entails significant organisational and technical shifts for cultural heritage institutions, particularly within the GLAM sector.

Finally, it is essential to distinguish between data spaces and data clouds. A data cloud is a technological deployment model for storing, processing and accessing data and services via networked infrastructures, typically managed by external service providers. A data space, by contrast, constitutes a socio-technical ecosystem comprising data sources, services, governance rules and participating actors, enabling secure, trusted and controlled data exchange. Many data spaces are implemented on cloud infrastructures. Data spaces are grounded in principles of interoperability, data sovereignty and shared standards, as exemplified by the evolving CEDSCH.

This paper examines how these conceptual principles are being operationalised through the development of cultural heritage data spaces in Europe. It focuses on national and transnational initiatives that can be analytically understood as data spaces and that are connected to broader European research infrastructures. Following an overview of the European policy framework, the paper reviews relevant research and presents a comparative analysis of selected European cultural heritage portal providers of cultural heritage data.

The development of data spaces within the European Union Member States reflects a broader transformation of European digital governance, in which data are increasingly framed as strategic resources requiring coordinated infrastructures, regulatory alignment and institutional cooperation. Rather than relying on centralised platforms or isolated national initiatives, the EU has promoted federated data ecosystems that enable cross-border interoperability while preserving national and institutional data sovereignty (European Union, 2020).

In the cultural heritage domain, this transformation unfolds within a particularly heterogeneous landscape. Member States differ significantly in terms of digitisation maturity, institutional capacity, legal frameworks and funding models. While some countries have established advanced national digital heritage infrastructures closely aligned with European initiatives, others remain dependent on project-based digitisation efforts with limited sustainability. As a result, the development of cultural heritage data spaces across the EU is uneven, shaped by national priorities, administrative structures and historical trajectories of heritage governance.

At the same time, European-level policy initiatives, supported by funding programmes have exerted a strong harmonising influence. Through funding programmes such as the Digital Europe Programme, Horizon Europe and the Connecting Europe Facility, Member States are encouraged to align national infrastructures with shared European standards, architectures and governance models. This alignment is particularly evident in the adoption of common metadata frameworks, rights statements and interoperability protocols developed within the Europeana ecosystem.

Within this multi-level governance context, national and transnational initiatives increasingly position themselves not merely as digitisation projects or access portals, but as components of an emerging European data space for cultural heritage. These initiatives typically emphasise federated architectures, standardised metadata and rights information and the potential for computational reuse of cultural heritage data. However, the extent to which they can be analytically classified as data spaces varies considerably, depending on their governance arrangements, technical maturity and degree of integration with European research infrastructures.

Against this background, the development of cultural heritage data spaces in the EU can be understood as an ongoing process of institutional, technical and legal convergence rather than a fully realised infrastructure. Examining national and international initiatives within this evolving landscape provides valuable insight into how data space principles are interpreted and implemented across different Member States.

The development of the CEDSCH is embedded within a comprehensive European policy framework addressing data governance, digital infrastructures, cultural policy, research and intellectual property. This framework reflects a paradigmatic shift in EU digital policy away from platform-centric access models towards federated, sovereign and interoperable data spaces designed to enable trusted data sharing and reuse across sectors and national borders.

A central driver of this shift is the European Strategy for Data, which introduced sectoral Common European Data Spaces as a cornerstone of Europe’s digital transformation agenda (European Commission, 2020). These data spaces are conceptualised as federated ecosystems that facilitate secure and interoperable data exchange while respecting sector-specific legal, ethical and economic constraints. Cultural heritage was explicitly identified as a strategic domain for this approach, owing to its societal relevance, institutional fragmentation and complex copyright and licensing environment.

This strategic vision was further articulated through Commission Recommendation (EU) 2021/ 1970 on a common European data space for cultural heritage (2021). The recommendation provides guidance to Member States and cultural heritage institutions on the establishment of a shared European data space and emphasises the adoption of common European standards, semantic models and technical frameworks. These include the Europeana Data Model (EDM), harmonised rights statements, such as those provided by RightsStatements.org, and interoperable publishing mechanisms defined by the Europeana Publishing Framework. Within this policy context, cultural heritage data are framed not merely as digital surrogates of collections, but as strategic data assets requiring governance structures, provenance control and sustainable infrastructures.

The policy framework for cultural heritage data spaces is reinforced by horizontal EU data legislation. The Data Governance Act (Regulation (EU) 2022 / 868) and the Data Act (Regulation (EU) 2023 / 2854) establish cross-sectoral principles for trusted data sharing, interoperability and access across public and private domains. These instruments provide the regulatory foundations for sovereign data exchange and data intermediation, which are essential for the operation of sectoral data spaces, including those in the cultural heritage domain.

In parallel, technical and conceptual reference frameworks developed by initiatives such as Gaia-X and the International Data Spaces Association have significantly influenced the architectural principles adopted in European data spaces. These frameworks promote decentralisation, interoperability and data sovereignty, offering governance and implementation models particularly suited to the heterogeneous and distributed nature of cultural heritage institutions.

The cultural heritage domain presents a number of specific challenges that further justify the adoption of a data space approach. These challenges include structural fragmentation across a large number of small and medium-sized institutions; complex copyright and licensing conditions requiring machine-readable rights management; long-term digital preservation in the context of rapidly evolving technologies; and the growing importance of large-scale, high-quality data sets for 3D digitisation and AI-based analysis. Addressing these challenges necessitates coordinated European infrastructures rather than isolated institutional or project-based solutions.

Against this backdrop, the European Commission has initiated the deployment of the CEDSCH under the Digital Europe Programme, building upon the Europeana ecosystem (European Commission, 2021; Commission Recommendation (EU) 2021 / 1970, 2021; European Commission, 2024). The data space aims to support federated data exchange among Member States, enhance digitisation capacities – particularly for 3D cultural assets – provide legal and ethical certainty for data providers and enable the reuse of cultural heritage data for research, education and innovation. In this sense, the CEDSCH functions as a connective layer between cultural institutions, research infrastructures and innovation ecosystems, facilitating semantic interoperability and computational use of heritage data.

A key operational component of this ecosystem is the European Collaborative Cloud for Cultural Heritage (ECCCH), supported by the European Cloud for Heritage OpEn Science project. The ECCCH is designed as a secure collaborative environment supporting shared tools, workflows and data sets for heritage professionals. Hosted by the Poznań Supercomputing and Networking Center, its architecture was set up in 2025, with phased deployment planned through 2029. Early project contributions, including AI-based tools and curated data sets, illustrate its role as an enabling infrastructure for data-driven cultural heritage research.

While distinct in governance and objectives, the cultural heritage data space is designed to interoperate with European research infrastructures. Platforms such as the European Open Science Cloud, OpenAIRE and D4Science provide cross-disciplinary research environments that may integrate with the CEDSCH when cultural heritage data are used in scientific contexts. In addition, ERIC-based infrastructures – including CLARIN, DARIAH, OPERAS and E-RIHS – play a critical role in connecting cultural heritage data with humanities and heritage science research.

Finally, the legal compatibility of cultural heritage data spaces with copyright law is supported by the Directive on Copyright in the Digital Single Market (Directive [EU] 2019 / 790). The Directive introduces exceptions that enable cultural heritage institutions to digitise and use works for preservation, research and educational purposes under defined conditions. This legal framework underpins the integration of copyrighted materials into controlled, rights-aware data space environments, rather than unrestricted access models.

Research on data spaces in the cultural heritage domain builds on the collections-as-data paradigm, which reconceptualises digitised and born-digital collections as computationally actionable data sets rather than static representations of physical objects. Early work by Padilla (2018) articulated this conceptual shift as foundational for enabling large-scale methods such as text and data mining, machine learning and network analysis. At the same time, Padilla identified a structural tension between scholarly values and emerging access models dominated by publishers and vendors, who increasingly restrict programmatic access through proprietary platforms and application programming interfaces (APIs). Such models, which allow the monitoring and monetisation of research queries, have been widely critiqued as incompatible with academic freedom and have prompted calls for community-owned, values-driven infrastructures.

These concerns were consolidated in the Vancouver Statement on Collections as Data (Padilla et al., 2023), which articulates 11 principles addressing responsible computational use, equity, participatory design, interoperability, transparency, sustainability and ethical engagement with AI. The Statement situates collections-as-data within a broader international context and explicitly links technical development to organisational commitments and long-term infrastructural investment, thereby anticipating key elements of later data space approaches. Complementing this normative framework, Candela et al. (2023) proposed a practical checklist of 11 criteria for creating and evaluating digital collections suitable for computational use within GLAM institutions.

Uzelac and Lovrinić Higgins (2025) conceptualise the value of cultural heritage in the digital age as a dynamic, multi-dimensional construct that emerges through use, reuse and societal impact, rather than through digitisation alone. This perspective aligns closely with the data space paradigm underpinning the CEDSCH, which reframes digital heritage from static content or access objects into governable, reusable and interoperable data assets. By emphasising the need to move “from data to impact,” the authors implicitly support the shift toward federated data infrastructures in which value is generated through trusted data sharing, computational reuse and cross-sectoral integration. Within this framework, cultural heritage data spaces function as enabling environments that allow cultural data to contribute to research, innovation, education and policy. Impact assessment thus becomes inseparable from questions of data governance, interoperability and sustainability. The study thus provides a conceptual bridge between cultural value assessment and the emerging European data space model, highlighting that the societal value of digital cultural heritage depends not only on access, but on the conditions that enable meaningful, lawful and scalable reuse within federated ecosystems across institutional, legal and technical dimensions. However, translating this conceptual shift into practice exposes persistent structural constraints.

Copyright and licensing remain central barriers to the operationalisation of collections-as-data. Dişli et al. (2025) demonstrate that copyright restrictions, non-standardised metadata and the absence of machine-readable licence information significantly hinder reuse, even for public-domain materials. They argue that collections-as-data require interoperable legal and semantic frameworks, including standardised rights statements, open licences and machine-readable metadata models. Lehmann and Sichani (2025) further show that access to copyrighted materials substantially improves AI model performance – particularly for complex language tasks – yet remains legally constrained. They propose regulated data spaces as a mechanism for reconciling data sovereignty, lawful access and potential remuneration, including through decentralised infrastructures such as Gaia-X. Empirical evidence from large language model training similarly confirms that high-quality copyrighted cultural data enhance performance, while simultaneously raising ethical and legal concerns that necessitate structured governance (De la Rosa et al., 2025).

Within this context, cultural heritage data spaces are increasingly conceptualised as federated data ecosystems rather than centralised repositories. Jarke (2023), in a case study of the German Data Space Culture initiative, defines such spaces as frameworks for sovereign data sharing that preserve institutional control while enabling value creation and fair value appropriation. This perspective aligns closely with EU-level developments. Verwayen and Aldana (2025) describe the evolution of the Europeana Initiative from an access-oriented portal to a reuse-focused platform and, more recently, to a data space explicitly oriented towards sovereignty, decentralisation and interoperability within the broader European data strategy.

Importantly, Europeana functions not only as a technical infrastructure but also as an instrument of cultural policy. Studies by Capurro and Plets (2021) and Capurro et al. (2024) demonstrate how Europeana’s metadata standards and governance frameworks actively shape institutional practices, interoperability norms, and cultural heritage narratives across Europe. These analyses underline that data models and standards operate as mechanisms of governance, embedding cultural, political and epistemic assumptions within technical infrastructures – an insight of direct relevance for the design of cultural heritage data spaces.

At the same time, critical perspectives question the extent to which Europeana can serve as a full-fledged cultural heritage data space. Turan and Sganga (2025) argue that while the CEDSCH aims to create a “single market for data” enabling broad cross-border sharing and reuse, Europeana was originally designed as a “single access point” for discovery. Treating Europeana as equivalent to a data space risks conflating fundamentally different infrastructural paradigms. This conflation raises legal and policy challenges, as the CEDSCH must comply with both EU data law and diverse national cultural heritage and copyright regimes – requirements that a discovery-oriented platform alone cannot satisfy.

Technical research complements these policy and legal analyses by demonstrating how interoperability and reuse can be achieved in practice. Linked Open Data approaches, semantic web technologies and knowledge graph architectures enable cross-collection querying, enrichment and integration at scale (Isaac and Haslhofer, 2013; Dressen, 2024). Evidence from scientific data spaces in other domains further confirms that federation, shared standards and governance are decisive success factors that can be transferred to the cultural heritage context (Sipos et al., 2024).

In summary, existing research reveals a clear conceptual progression from digitisation and access, through collections-as-data, to cultural heritage data spaces conceived as sovereign, federated and interoperable infrastructures. While substantial advances have been made in articulating principles, legal frameworks and technical foundations, significant challenges remain with regard to sustainable governance, equitable participation and the responsible integration of AI. These unresolved issues underscore the need for further research that approaches data space design as a socio-technical and policy-aligned endeavour rather than a purely technical solution.

This research is grounded in a systematic EU’s policy review and legislative instruments that support the development of data spaces for cultural heritage. Building on this policy analysis, the study examines existing practical initiatives across European countries to assess the current state of national cultural heritage data aggregation services and related infrastructures. Particular attention is given to their level of interoperability maturity, their relevance for the development of the CEDSCH, and their alignment with open science principles and FAIR data management practices.

In this context, it is essential to clarify what is meant by data space participation. In this study, data space participation is understood not as the mere provision of digital access through aggregation portals, but as the capacity of an infrastructure to operate as a governed node within a federated European ecosystem (Otto et al., 2022). In line with the European Commission’s concept of common data spaces as governance-driven infrastructures for trusted sharing (European Commission, 2025), participation entails:

• formal participant roles and onboarding mechanisms;

• compliance with trust and sovereignty frameworks such as Gaia-X (Gaia-X Association, 2022); and

• technical interoperability through common architectural building blocks defined by the Data Spaces Support Centre (DSSC, 2025).

Thus, readiness is evaluated not only through discoverability, but through the extent to which portals enable machine-actionable, policy-governed reuse within the CEDSCH (European Commission, 2025).

The primary objective of the analysis is to evaluate national portals and aggregation services that provide access to digitised cultural heritage data, with a view to assessing their potential contribution to the emerging CEDSCH framework. In doing so, the study aims to identify patterns of convergence and fragmentation within the European cultural data ecosystem and to highlight structural strengths and gaps across national contexts.

The analytical framework is informed by the Vancouver Statement on Collections-as-Data (Padilla et al., 2023) and by the criteria proposed by Candela et al. (2023) in their checklist for creating and evaluating digital collections suitable for computational use. These established criteria were complemented by additional dimensions considered essential for the categorisation and assessment of cultural heritage data infrastructures, particularly with regard to the scope and nature of the data provided.

On this basis, the paper develops an evaluative framework of 12 criteria (C1–C12) to benchmark portal readiness, understood as the capacity of portals to provide collections suitable for computational use by supporting the FAIR principles across institutional, technical, legal and organisational dimensions:

• Institutional and strategic framework.

  • Provider institutions and governance, examining the institutional nature of data providers (libraries, archives, museums, research infrastructures or consortia), as well as governance arrangements, long-term stewardship and clarity of institutional responsibilities.

  • Scope and types of data, assessing the extent, diversity and coherence of the collections in terms of covered domains, temporal and geographic range and supported media formats (e.g. text, images, audiovisual materials, 3D objects, research data).

  • Access conditions and licensing, evaluating the openness, transparency and legal clarity of access and reuse conditions, including access regimes and machine-readable licences (e.g. CC0, CC BY).

• Identification, documentation and use of standards.

  • Persistent identification and citation, examining the use of persistent identifiers (PIDs), such as DOIs, and the provision of clear citation recommendations to support scholarly reuse and reproducibility.

  • Documentation and transparency, evaluating the availability and quality of documentation describing sources, data granularity, digitisation workflows, data cleaning and transformation processes, quality considerations and intended uses.

  • Standardisation, interoperability and semantic enrichment, assessing the adoption of recognised metadata standards, schemas and protocols (e.g. Dublin Core, MARC, schema.org, DCAT, RDF-based vocabularies), as well as the use of controlled vocabularies, authority files and linked data approaches.

• Technical accessibility and reuse.

  • Technical accessibility and programmatic access, assessing the availability and quality of portals, bulk downloads, exports, APIs and other programmatic interfaces enabling scalable reuse.

  • Support for digital humanities and computational research, examining the availability of tools, datasets and services that enable text and data mining, network analysis, image analysis and other computational methods.

  • FAIR alignment (synthesis criterion), evaluating the overall compliance with the FAIR principles (Findable, Accessible, Interoperable, Reusable) across identifiers, access, interoperability, licensing and documentation.

• Trustworthiness, community and innovation.

  • Collaborative curation and community engagement, evaluating integration with collaborative platforms and opportunities for shared curation, annotation, and enrichment.

  • Innovation support and alignment with European data spaces, assessing enablement of advanced uses (e.g. AI and machine learning, semantic enrichment, large-scale image analysis and 3D technologies) and alignment with the principles, standards and governance models of the CEDSCH.

  • Digital preservation, provenance and authenticity, examining institutional preservation strategies, provenance metadata, versioning practices and mechanisms ensuring long-term integrity.

Taken together, these criteria provide a structured framework for evaluating digital collections not merely as digitised assets, but as heritage data capable of operating within federated, sovereign and reusable data spaces. The framework enables comparative assessment across institutions and national contexts while integrating technical, legal and organisational dimensions of data stewardship.

For the empirical component of the study, an initial mapping of national providers of digital cultural heritage data was conducted across EU Member States and at the EU level. In this first step, 35 national and transnational cultural heritage portals and digital heritage infrastructures from 22 European countries and the EU were identified and reviewed. Based on this exploratory assessment, a subset of 17 portals and digital heritage infrastructures from 14 European countries and the EU was selected as the analytical sample for in-depth evaluation. The primary selection were the scope and diversity of the available content, as well as the presence of key features relevant to computational use and research support. In addition, portals that functioned solely as Europeana aggregators were excluded.

The selection was guided by the portals’ national or sectoral coordination role, their relevance for cross-institutional aggregation, and their potential contribution to the emerging CEDSCH. From October to December 2025, each portal in the final sample was evaluated qualitatively through a document-based review using publicly available sources, including policy documents, technical documentation, platform descriptions, and metadata guidelines.

Each portal was assessed using a three-level ordinal scoring scheme (0–2) across all criteria (C1–C12). The scoring approach was adopted to enable comparative benchmarking of national cultural heritage aggregation services and to capture varying degrees of infrastructural readiness in relation to the emerging CEDSCH.

To enhance transparency and reproducibility, scores were assigned on the basis of observable portal functionality and publicly available institutional documentation, including official policy statements, metadata access conditions, licensing declarations and technical interface descriptions. The scoring scheme distinguishes between absent, partially implemented and systematically implemented features in line with FAIR-oriented and data space governance expectations.

Across all criteria, “partial implementation” (Score 1) refers to cases where a feature exists only for selected collections, lacks machine-actionable form, or is provided without clear reuse conditions. “Full implementation” (Score 2) refers to cases where the feature is systematically available across the portal, explicitly documented, and technically accessible for reuse (e.g. through APIs, persistent identifiers or structured licensing).

Scoring decisions were guided by an explicit operational scoring rubric and predefined thresholds (refer to Table 1), ensuring consistency across cases.

Given the study’s reliance on publicly accessible evidence, the assessment reflects documented infrastructural readiness rather than independently audited technical performance. Nonetheless, the scoring framework provides a structured approximation of current portal capacities and identifies areas where further development would be required to support machine-actionable, policy-governed reuse within the federated cultural heritage data space ecosystem. However, future research should incorporate structured interviews or questionnaires with national coordinators and infrastructure operators to validate and refine the findings

By systematically mapping European cultural heritage data infrastructures against a shared set of criteria, this study provides a foundation for identifying best practices and structural gaps in digital heritage aggregation, and for informing the integration of national nodes into the CEDSCH.

The analysed portals represent national or regional nodes that contribute to the emerging CEDSCH. They integrate museums, libraries, archives and other cultural institutions, acting as data aggregators and service providers. Their development reflects the diversity of digital maturity and policy frameworks across Europe, yet they share common objectives of openness, interoperability and research support. In the analysis, we included those countries with portals that were not just Europeana aggregators to, but had some kind of national coordination role among cultural heritage institutions, mainly GLAM, i.e. Austria (Kulturpool), Belgium (meemoo and Bibliothèque Royale de Belgique (KBR) Digital Collections), Czech Republic (Czech Digital Library), Denmark (Royal Danish Library and National Museum), Estonia (e-Varamu), Finland (Finna.fi), France (Gallica), Germany (Deutsche Digitale Bibliothek – DDB), Ireland (Digital Repository of Ireland – DRI), Italy (CulturaItalia), Norway and Sweden (DigitaltMuseum), Poland (Federacja Bibliotek Cyfrowych – FBC), Slovenia (Digital Library of Slovenia – dLib.si), Spain (HispanaPRO), Sweden (Swedish Open Cultural Heritage - SOCH) and UK (Museum Data Service). For comparative reasons, the Europeana portal is included in the analysis.

The comparative analysis of selected European cultural heritage portals reveals a set of distinct but complementary governance and access models (refer to Table 2). The majority of infrastructures follow a federated aggregation model, in which a centrally coordinated infrastructure integrates metadata and, in some cases, content from a heterogeneous landscape of libraries, archives, museums and other heritage institutions. Examples such as Kulturpool (Austria), Finna.fi (Finland), Deutsche Digitale Bibliothek (Germany), CulturaItalia (Italy), HispanaPRO (Spain), SOCH (Sweden) and Europeana at the supranational level illustrate a common pattern of distributed data provision combined with central coordination. This model supports national and cross-border interoperability and is conceptually well aligned with the architectural principles of the CEDSCH, yet it also introduces variability in data quality, licensing practices and documentation, reflecting the diverse institutional capacities of contributing organisations.

A smaller but strategically significant group of infrastructures follows a single-institution or tightly governed repository model, most notably Gallica in France and the Digital Repository of Ireland, KBR Digital Collections, and the Digital Library of Slovenia. These infrastructures benefit from clearly defined institutional mandates, long-term stewardship responsibilities, and coherent collection development policies. As a result, they tend to offer more consistent documentation, preservation strategies, and reuse conditions. However, their coverage is often institutionally bounded, requiring complementary aggregation layers to achieve comprehensive national or cross-domain coverage. This tension between coherence and breadth underscores a structural trade-off within European cultural heritage infrastructures: centralised governance enhances stability and data quality, while federated aggregation maximises coverage and inclusivity.

In terms of data scope, the analysis identifies three dominant patterns. Library-centric infrastructures (e.g. Gallica, the Czech Digital Library, Digital Library of Slovenia, and parts of Federacja Bibliotek Cyfrowych) provide extensive textual collections with strong potential for computational reuse in digital humanities research, particularly through optical character recognition (OCR)-enabled collections. Museum- and object-oriented platforms (such as DigitaltMuseum and the UK Museum Data Service) prioritise material culture and object-level metadata, often with rich descriptive records but less extensive textual corpora. Finally, national cross-domain aggregators (e.g. Finna.fi, DDB, Swedish Open Cultural Heritage, Europeana) integrate heterogeneous data types across sectors, offering broad discovery layers that support interoperability but often depend on external providers for full content access and licensing clarity.

With regard to access conditions and licensing, most infrastructures adopt hybrid access models. Metadata are typically openly accessible – often under CC0 or similar public-domain dedication – while access to digital objects and reuse rights varies according to the policies of contributing institutions. Strongly curated repositories such as the Digital Repository of Ireland and Gallica tend to provide clearer and more consistent licensing frameworks, whereas large-scale aggregators reflect the heterogeneous legal environments of their providers.

Overall, the analysis indicates that European cultural heritage portals form a complementary and multi-layered ecosystem, in which federated aggregators, institutional repositories, and sector-specific platforms collectively contribute to the emerging CEDSCH.

The comparative analysis (refer to Table 3) demonstrates that the use of persistent identifiers (C4), documentation practices (C5), and the adoption of standards (C6) constitute a major differentiating factor between discovery-oriented portals and infrastructures designed for systematic data reuse. While most European cultural heritage portals provide stable item-level identifiers, the use of formal persistent identifier systems – such as DOIs or data set-level citation mechanisms – remains uneven. In many cases, item identifiers take the form of persistent URLs or internal identifiers that ensure stable linking within the portal environment, but are not registered in global PID systems or accompanied by standardised citation metadata. As a result, they support basic referencing and discovery, yet do not always enable reliable data set-level citation, versioning, or long-term scholarly reuse. Aggregation-oriented infrastructures typically rely on persistent URLs generated within portal environments, which support stable referencing but do not always provide formal citation recommendations or data set-level identifiers. In contrast, research-oriented repositories and a small number of advanced national infrastructures, such as the Digital Repository of Ireland or Gallica, provide clearer citation frameworks, sometimes including DOIs and explicit reuse guidance, thereby supporting reproducibility and scholarly referencing practices.

Documentation and transparency practices (C5) vary significantly across the analysed portals. At the lower end of the spectrum, some aggregation platforms provide only basic descriptive or technical information, often limited to user-facing help pages or high-level metadata descriptions. More advanced infrastructures offer structured technical documentation, API descriptions, data models, and workflow explanations. Platforms such as Finna.fi, SOCH, Europeana and the Digital Repository of Ireland demonstrate advanced documentation practices, including detailed descriptions of data models, harvesting processes and transformation pipelines. Such documentation is essential for enabling computational reuse as it reduces interpretive uncertainty and supports reproducibility across research contexts.

Standardisation, interoperability and semantic enrichment (C6) represent an area of relatively strong alignment across European infrastructures, although with varying levels of maturity. Most portals rely on widely recognised metadata standards, such as Dublin Core or MARC-derived schemas, often combined with sector-specific or national data models. Large aggregation infrastructures – including Deutsche Digitale Bibliothek, Finna.fi, SOCH and Europeana – demonstrate more advanced interoperability practices, incorporating linked data approaches, authority files and RDF-based models. Europeana, in particular, provides a mature semantic framework through the EDM, which facilitates cross-domain integration and machine-actionable metadata. In contrast, smaller or library-centric infrastructures often rely on traditional bibliographic standards, with often limited semantic enrichment and linked data integration.

Taken together, the findings indicate that persistent identification, transparent documentation and standards-based interoperability are central to the transition from discovery portals to data space-ready infrastructures. While most portals provide stable object-level identifiers and basic metadata standardisation, only a subset offers data set-level identification, formal citation guidance, and comprehensive technical documentation. These features significantly enhance reproducibility, interoperability and long-term reuse, and therefore constitute critical enabling conditions for the development of CEDSCH.

The comparative analysis (refer to Table 4) reveals substantial variation in the extent to which European cultural heritage portals provide technical infrastructures that support scalable reuse and computational research. While most portals enable human-oriented discovery and browsing, only a subset offers the programmatic interfaces, bulk access mechanisms and technical services required for systematic data reuse.

With regard to technical accessibility and programmatic access (C7), three main patterns emerge. First, a group of API-first or technically mature infrastructures – including SOCH, DigitaltMuseum, Finna.fi, Gallica, the Digital Repository of Ireland and Europeana – provide well-documented APIs, structured exports or bulk data sets. These platforms support automated data retrieval and large-scale analysis, making them well aligned with data space architectures. Second, several national aggregation portals, such as Kulturpool, CulturaItalia, HispanaPRO, and the Czech Digital Library, provide stable discovery environments but only limited APIs or bulk access mechanisms, often relying on Open archives initiative protocol for metadata harvesting (OAI-PMH) endpoints or provider-level services. Third, institution-based platforms, such as those of the Royal Danish Library or KBR, offer programmatic access at the institutional level rather than through a unified national interface, resulting in fragmented reuse pathways.

Support for digital humanities and computational research (C8) follows similar structural patterns. Library-led and research-oriented infrastructures – most notably Gallica, Finna.fi, the Digital Repository of Ireland and Digital Library of Slovenia – provide large-scale OCR corpora, curated data sets or dedicated research services that facilitate text and data mining. API-driven museum or heritage platforms, such as DigitaltMuseum and SOCH, enable computational reuse through machine-readable metadata and image services and are increasingly used in machine learning and data science contexts. In contrast, many aggregation portals primarily function as discovery layers, with computational reuse delegated to downstream services or contributing institutions. In such cases, reuse is technically possible but not systematically supported at the portal level.

FAIR alignment (C9), considered as a synthesis criterion, reflects the cumulative effects of identifiers, access models, interoperability practices, licensing and documentation. Portals that combine persistent identifiers, open metadata, standardised schemas, clear licensing and robust APIs – such as Europeana, Finna.fi, Gallica, the Digital Repository of Ireland and SOCH – demonstrate strong overall alignment with the FAIR principles. In contrast, aggregation portals with limited programmatic access or fragmented licensing frameworks tend to achieve only partial FAIR alignment, despite providing stable identifiers and basic metadata interoperability.

Taken together, the findings indicate that the readiness of cultural heritage portals for data space integration depends less on the presence of digital collections alone than on the availability of machine-actionable access layers. Portals that provide well-documented APIs, bulk data access and research-oriented services are significantly better positioned to support digital humanities, AI and other data-driven methods. Advancing toward the CEDSCH will, therefore, require not only continued digitisation but also the systematic development of programmatic access, reusable data sets, and FAIR-compliant technical infrastructures.

The comparative analysis (refer to Table 5) indicates that innovation capacity and alignment with CEDSCH are closely interrelated across European cultural heritage portals. While many infrastructures support experimental or computational uses to varying degrees, their readiness to participate in a federated data space depends not only on technical capabilities but also on governance models, interoperability practices and data-sharing mechanisms.

Collaborative curation and community engagement (C10) remain relatively underdeveloped across the analysed portals. Most infrastructures prioritise professional, institution-led curation, with limited opportunities for public annotation or crowdsourced enrichment. Notable exceptions include Europeana, Gallica and the Digital Repository of Ireland, which have experimented with crowdsourcing campaigns or collaborative research environments. Sector-oriented infrastructures, such as DigitaltMuseum and the Museum Data Service, support collaboration primarily at the institutional or professional network level.

With regard to innovation support and alignment with the CEDSCH (C11), most portals demonstrate at least a conceptual alignment often reflected in participation in Europeana aggregation workflows, adoption of shared metadata standards, and adherence to European interoperability frameworks. This contributes to a common technical baseline that enables cross-border discovery and metadata exchange. However, operational alignment – including machine-actionable licensing, APIs, data set-level access and controlled data sharing – remains uneven. A small group of infrastructures, such as Europeana, SOCH, Finna.fi and the Digital Repository of Ireland, show strong alignment with data space principles and actively support advanced uses, including AI, machine learning and large-scale computational analysis. In contrast, many national aggregation portals continue to function primarily as discovery layers, with innovation activities occurring downstream at institutional or research levels.

Digital preservation, provenance and authenticity (C12) are predominantly addressed at the level of individual institutions rather than national aggregation portals. National libraries and trusted digital repositories – such as Gallica, the Digital Repository of Ireland and the Digital Library of Slovenia – demonstrate the most mature preservation strategies, including documented workflows, versioning practices, fixity controls and explicit provenance metadata. Aggregation infrastructures, in contrast, typically preserve metadata while delegating long-term preservation of digital objects to contributing institutions, resulting in variable authenticity guarantees across the ecosystem.

Taken together, the findings suggest that alignment with the CEDSCH is widely present at a conceptual level, but only a limited number of infrastructures currently operate as fully data space–ready nodes. Strengthening machine-actionable services, preservation transparency, and collaborative data practices will be essential for ensuring that cultural heritage portals can participate effectively in federated European data ecosystems.

All selected European portals were scored using a 0–2 scoring (2 = strong evidence, 1 = partial, 0 = unclear or not evident) across the consolidated criteria C1–C12. The results are presented in Table 6.

The comparative scoring of European cultural heritage portals reveals an ecosystem characterised by strong institutional anchoring, broad national coverage and mature aggregation infrastructures, combined with more uneven performance in reuse-oriented, participatory and innovation-related dimensions. High scores are most consistently observed in criteria related to provider institutions and governance (C1), scope and types of data (C2) and standardisation and interoperability (C6), reflecting the long-term public investment of European countries in national digitisation programmes and the widespread adoption of shared metadata standards aligned with the Europeana ecosystem.

Most infrastructures are embedded within stable public-sector organisations – such as national libraries, ministries or sectoral heritage consortia – and operate within clearly defined institutional mandates. This results in consistently strong performance in governance-related criteria, as well as in collection scope, particularly in national cross-domain aggregators such as Finna.fi, the Deutsche Digitale Bibliothek and Europeana. Similarly, the adoption of standardised metadata schemas and aggregation workflows has enabled strong performance in interoperability-related criteria across many portals, even where semantic enrichment remains limited.

Scores are lower, however, for criteria addressing access conditions and licensing for reuse (C3), persistent identification and citation (C4) and, to a lesser extent, documentation and transparency (C5). While stable object-level identifiers are common, data set-level persistent identifiers and formal citation guidance remain largely confined to research-oriented repositories, most notably the Digital Repository of Ireland. Licensing practices across aggregation portals are frequently heterogeneous and dependent on contributing institutions, resulting in only partial support for automated or large-scale reuse.

The most pronounced differentiation among portals appears in criteria related to technical accessibility and programmatic access (C7), support for digital humanities and computational research (C8) and overall FAIR alignment (C9). A limited group of infrastructures – including Europeana, SOCH, Finna.fi, Gallica, DigitaltMuseum, and the Digital Repository of Ireland – provide well-documented APIs, bulk data access or computationally oriented services, positioning them as more advanced nodes in terms of reusable and machine-actionable data. In contrast, many national aggregation portals provide stable discovery environments but only limited programmatic access, often relying on basic harvesting interfaces or provider-level services.

Criteria within the dimension of innovation, community, and trustworthiness (C10–C12) display the greatest variability. Collaborative curation and community engagement (C10) remain relatively underdeveloped, with most portals. The prevailing model prioritises professional, institution-led curation, with only limited opportunities for public annotation, crowdsourcing or shared enrichment. Where collaboration exists, it is often restricted to institutional networks or pilot initiatives rather than embedded as a core infrastructural feature.

Innovation support and alignment with the CEDSCH (C11) are widely articulated at the conceptual level, but operational implementation remains uneven. Most portals demonstrate formal alignment through participation in Europeana aggregation workflows and the adoption of shared standards. However, only a smaller group – particularly Europeana, SOCH, Finna.fi, the Digital Repository of Ireland and Gallica – exhibit the combination of machine-actionable licensing, robust APIs and data set-oriented services that characterise fully data space–ready infrastructures.

Digital preservation, provenance and authenticity (C12) are typically addressed at the level of contributing institutions, with aggregation portals focusing primarily on metadata exchange and discovery. As a result, preservation transparency and versioning practices vary considerably across the ecosystem. Repository-oriented infrastructures and national libraries tend to provide the strongest preservation guarantees, while aggregation services depend on the policies of their providers.

Taken together, the C1–C12 scoring matrix demonstrates that European cultural heritage portals form a heterogeneous but complementary ecosystem. Aggregation-centric infrastructures provide strong foundations for discovery and interoperability, while repository-oriented and API-first platforms deliver more advanced reuse capabilities. Future development should therefore prioritise reuse-oriented access layers, persistent identification strategies, semantic enrichment, participatory governance, and operational alignment with the CEDSCH. These dimensions will be essential for the transition from metadata aggregation platforms to fully operational nodes within federated European cultural data spaces.

The comparative analysis confirms that European cultural heritage portals constitute a structurally mature but functionally heterogeneous ecosystem. Most infrastructures demonstrate long-term investment in digitisation, national coordination, and aggregation-grade interoperability, often through participation in Europeana-aligned workflows and the adoption of shared standards. This is reflected in consistently strong performance for governance and institutional anchoring (C1), scope and breadth of collections (C2), and standards-based interoperability (C6).

However, the findings clearly show that aggregation maturity does not automatically translate into CEDSCH readiness. Readiness for participation in a federated data space requires more than discoverability: it depends on machine-actionable reuse conditions (C3), programmatic access and scalable technical affordances (C7), reuse-oriented research support (C8) and coherent FAIR alignment (C9) – all of which are implemented unevenly across the sample.

Only a limited subset of infrastructures combines strong performance across these criteria, while many portals continue to operate primarily as discovery gateways. In these cases, programmatic access is limited, licensing remains provider-dependent, and reuse pathways are not systematically integrated into the portal architecture. This confirms a structural distinction between aggregation maturity and operational data space readiness: the former is widespread, while the latter is concentrated in a smaller group of technically and institutionally advanced nodes.

Based on the qualitative synthesis across the four analytical blocks (C1–C12), the evaluated portals can be interpreted as occupying complementary roles rather than competing to deliver identical functions:

• Data space–ready node leaders: A limited group combines strong institutional governance (C1), coherent scope (C2), mature technical access (C7), explicit support for computational reuse (C8) and high FAIR alignment (C9), alongside clearer innovation pathways linked to the CEDSCH (C11). This group includes infrastructures such as Europeana, SOCH, Finna.fi, the Digital Repository of Ireland, and, in certain respects, Gallica and DigitaltMuseum. These portals illustrate what operational participation in a data space can look like: stable APIs and bulk access, clearer licensing logics, consistent documentation, and reuse-oriented services alongside human-facing discovery layers.

• CEDSCH-aligned aggregators requiring reuse upgrades: a larger group of national aggregation portals is well positioned as federated nodes, but remains constrained by partial implementation of reuse infrastructure. These portals generally perform strongly in governance, scope, and aggregation-grade interoperability (C1–C2, C6), yet exhibit weaker results in programmatic access (C7), computational reuse (C8) and innovation alignment (C11). Their alignment with the CEDSCH is therefore often conceptual and aggregation-centred rather than operationally reuse-centred.

For these portals, the strategic priority is not expanding coverage – often already strong – but strengthening the reuse stack: clearer access and licensing conditions (C3), more systematic documentation (C5), stronger programmatic access (C7) and more explicit computational research pathways (C8):

• Sectoral or specialist infrastructures as service nodes: museum- or audiovisual- or domain-specific infrastructures generate high value within their sectors, often with robust professional governance and strong preservation practices. Their main challenge is not national breadth, but cross-domain interoperability, licensing consistency, and integration into federated reuse environments. Within CEDSCH architecture, such infrastructures may be best understood as specialist service nodes, provided their APIs, rights frameworks, and metadata models remain compatible with shared European interoperability and governance expectations.

One of the most consistent findings concerns the strength – and limitation – of standardisation and interoperability (C6). Across the sample, recognised schemas and protocols enable effective harvesting and cross-border discovery. This reflects the success of Europeana-driven standardisation efforts and the widespread adoption of common aggregation models.

Yet, interoperability is frequently implemented at a minimum viable level for metadata exchange rather than for semantic integration and advanced reuse. Performance in areas related to computational reuse (C8) and FAIR alignment (C9) is more uneven, indicating that machine-actionable semantics, linked data practices and consistent modelling decisions remain concentrated in a smaller number of infrastructures.

For the CEDSCH, interoperability should, therefore, be understood not merely as metadata exchange, but as the ability to support cross-collection reasoning, reproducible reuse workflows, and machine-actionable data services. This requires closer coupling between standards (C6), documentation (C5) and programmatic access (C7).

Across the ecosystem, access for human discovery is generally mature, but reuse-oriented access remains uneven. The central structural gap lies in the incomplete integration of the conditions that make reuse scalable and reproducible: predictable access and licensing (C3), robust technical affordances (C7), reusable DH and computational services (C8) and end-to-end FAIR alignment (C9).

This pattern reveals a persistent separation between human-facing portals and machine-facing reuse layers. Even where APIs exist, reuse pathways are not always easy to locate, consistently documented or stable enough to support longitudinal research and automated workflows. In many aggregation portals, reuse continues to depend on downstream providers rather than on portal-level services.

Bridging this separation is essential if the CEDSCH is to function as more than an enhanced discovery layer. Without systematic reuse infrastructure, portals risk remaining peripheral nodes within a federated data ecosystem.

The criteria related to trustworthiness, community and innovation (C10–C12) show the greatest variability and clarify what is still missing for sustained federated reuse:

• Collaborative curation and community engagement (C10) remain relatively underdeveloped. The prevailing governance model still prioritises professional, institution-led curation, with limited mechanisms for public annotation or shared enrichment. From a data space perspective, participation should be reframed not only as engagement, but as a data quality and sustainability strategy, implemented through role-based contribution models that preserve institutional trust.

• Innovation support and alignment with the CEDSCH (C11) are widely articulated at the conceptual level but uneven operationally. Many portals align through Europeana-driven aggregation and shared standards, yet only a subset provides machine-actionable services, dataset-level access or innovation-ready datasets suitable for AI or large-scale computational use. Moving toward operational alignment therefore requires embedding innovation as a stable infrastructural function rather than a series of time-limited pilot projects.

• Preservation, provenance and authenticity (C12) are typically managed by contributing institutions rather than aggregation portals. While this division of responsibility is structurally understandable, it introduces uncertainty for federated reuse unless aggregators more clearly signal provenance chains, versioning practices and preservation responsibilities. In data space contexts, these signals become prerequisites for trust and reproducibility.

Taken together, the findings suggest that European portals already provide a strong foundation for a federated cultural data ecosystem. However, future development should prioritise a set of structural upgrades that address the most persistent gaps:

• Reuse-oriented access layers (C3, C7): stable APIs/bulk access, clearer reuse pathways and consistent machine-readable rights signals.

• Documentation as infrastructure (C5): transparent data models, workflows, transformations and quality signals that support reproducibility.

• Participatory enrichment with governance (C10): community contribution models that strengthen data quality while maintaining institutional trust.

• Operational CEDSCH alignment (C11): moving from aggregation compliance to federated reuse participation, including controlled sharing, data sovereignty, machine-actionable services.

• Trust and traceability signals (C12): clearer provenance chains, versioning visibility and preservation responsibilities across federated environments.

Overall, the analysis supports the conclusion that European cultural heritage portals constitute a complementary ecosystem with different infrastructural strengths. The transition toward fully operational CEDSCH nodes will depend less on expanding digitisation per se, and more on strengthening the conditions that make cultural heritage data reliably reusable, semantically coherent, and trustworthy within federated European environments.

This study relies exclusively on publicly available documentation and secondary sources. As a result, the assessment reflects declared rather than fully operational capabilities. Some portals may provide reuse or interoperability features that are not clearly documented, while others may overstate readiness in policy narratives. Consequently, the findings should be interpreted as an evaluation of visible infrastructural maturity rather than a definitive audit of technical implementation.

Future research should complement this analysis with structured interviews or surveys involving national coordinators, technical leads, and policy stakeholders to validate findings, assess implementation depth, and capture planned developments. In addition, the C1–C12 framework could be operationalised into measurable indicators – such as the presence and quality of API documentation, machine-readable licensing coverage, authority control adoption or availability of bulk download endpoints – to enable reproducible benchmarking and longitudinal comparison over time.

This study demonstrates that Europe already possesses a dense and institutionally robust landscape of cultural heritage portals capable of contributing to the CEDSCH. The principal challenge is not the absence of infrastructures or standards, but the uneven adoption of reuse-by-design practices: persistent identification, machine-readable licensing, semantic enrichment, computational access and explicit trust signals for provenance and preservation.

The findings suggest that the CEDSCH should not be conceived as a new infrastructure imposed uniformly on national systems. Rather, it should be understood as a federated ecosystem that builds on existing capacities while accommodating differentiated roles, including national aggregators, repository-grade data providers, and specialist sectoral nodes. Targeted investment in reuse-oriented layers – particularly within aggregation-centric portals – would yield disproportionate benefits, transforming conceptual alignment into operational participation.

In this sense, the CEDSCH constitutes an opportunity to enhance, federate, and align existing national infrastructures, enabling them to function not only as discovery platforms but as a coherent, trusted and sustainable European data ecosystem for cultural heritage.