The term Digital Library refers to a wide array of different organisations and collections that share the common trait of exposing digital content to a community of users. Digital libraries are applied in many different contexts ranging from academic institutions to public libraries, archives, museums and industries. The type of content that is stored in digital libraries varies depending on the organisation, it can either be reproduction of physical objects or content which is "born digital". Usually a digital library has two main functions: to store and preserve content and to deliver it to end users, being it a human consumer or another software application. Until today most digital libraries (DLs) only took limited advantage of the benefits that modern computing technologies offer.

To overcome this bottleneck, research and development for digital libraries include processing, dissemination, storage, search and analysis of all types of digital information. Traditional digital library applications are nowadays facing three new key challenges:

• size and searching: due to the high rate of the data that digital libraries can store it has become very difficult for the users to find and retrieve relevant content;
• interoperability: re-using, re-purposing, and re-mixing digital objects in heterogeneous environments is becoming a primary need of the users. Additionally, due to the fast increasing level of integration of IT infrastructures, digital libraries are now consumed and manipulated at the same time by human actors and by machines and other software applications;
• linking: the value of digital libraries multiplies according to the relations that link their objects to other digital objects, also outside the boundaries of a single digital repository.

Semantic Web technologies are a promising solution to meet the challenges that nowadays are faced by all digital libraries and digital content repositories, by:

• helping users to manage large and heterogeneous data sets with semanticenhanced searching;
• maximising interoperability of content by making semantics of the digital objects and their relations explicit and tractable by machines and software agents;
• enriching the context around the objects by semantically annotating the objects themselves and their links with other content, within and outside the boundaries of a library (Linked Data).