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Since the introduction of the term hypertext in the early 1960s, the goal has been to link, annotate as well as transclude parts of documents. However, most existing document linking approaches show some shortcomings in terms of the offered link granularity and cannot easily be extended to support new document formats. More recently, we see new document formats such as the Office Open XML (OOXML) standard which facilitate the linking to parts of certain document formats. We present a dynamically extensible open cross-document link service enabling the linking and integration of arbitrary documents and multimedia content. In our link browser, emerging document formats are supported via visual plug-ins or by integrating third-party applications via gateways. The presented concepts and architecture for dynamic extensibility improve the document life cycle in so-called cross-media information spaces and enable future-proof cross-document linking.

Documents do often not exist in isolation but are implicitly or explicitly linked to parts of other documents. However, due to a multitude of proprietary document formats with rather simple link models, today's possibilities for creating hyperlinks between snippets of information in different document formats are limited. In previous work, we have presented a dynamically extensible cross-document link service overcoming the limitations of the simple link models supported by most existing document formats. Based on a plug-in mechanism, our link service enables the linking across different document types. In this paper, we assess the extensibility of our link service by integrating some document formats as well as third-party document viewers. We illustrate the flexibility of creating advanced hyperlinks across these document formats and viewers that cannot be realised with existing linking solutions or link models of existing document formats. A user study further investigates the user experience when creating and navigating cross-document hyperlinks. CCS CONCEPTS• Human-centered computing → User studies; User centered design; • Applied computing → Hypertext / hypermedia creation; Document management;

General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal Take down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

With the rapid increase of digital information we are dealing with in our daily work, we face significant document retrieval and discovery challenges. We present a novel document retrieval and discovery framework that addresses some of the limitations of existing solutions. An innovative aspect of our solution is the combination of implicit and explicit links between documents in the retrieval as well as in the visualisation process, in order to improve document retrieval and discovery. Our framework exploits implicit relationships between documents-defined by the similarity of their content as well as their metadata-and explicit links (hyperlinks) defined between documents based on a third-party link service. Further, the software framework can be extended with arbitrary third-party visualisations. Last but not least, our search query interface offers advanced features not available in most existing document retrieval systems.