The term “Linked Data” refers to a set of best practices for publishing and connecting structured data on the Web. These best practices have been adopted by an increasing number of data providers over the last three years, leading to the creation of a global data space containing billions of assertions— the Web of Data. In this article, the authors present the concept and technical principles of Linked Data, and situate these within the broader context of related technological developments. They describe progress to date in publishing Linked Data on the Web, review applications that have been developed to exploit the Web of Data, and map out a research agenda for the Linked Data community as it moves forward.

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Linked Data - the story so far

The emergence of ubiquitous computing as a new design paradigm poses significant challenges for human-computer interaction (HCI) and interaction design. Traditionally, HCI has taken place within a constrained and well-understood domain of experience—single users sitting at desks and interacting with conventionally-designed computers employing screens, keyboards and mice for interaction. New opportunities have engendered considerable interest in “context-aware computing”—computational systems that can sense and respond to aspects of the settings in which they are used. However, considerable confusion surrounds the notion of “context”—what it means, what it includes and what role it plays in interactive systems. This paper suggests that the representational stance implied by conventional interpretations of “context” misinterprets the role of context in everyday human activity, and proposes an alternative model that suggests different directions for design.

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What we talk about when we talk about context

The proliferation of computing into the physical world promises more than the ubiquitous availability of computing infrastructure; it suggest new paradigms of interaction inspired by constant access to information and computational capabilities. For the past decade, application-driven research on abiquitous computing (ubicomp) has pushed three interaction themes:natural interfaces, context-aware applications,andautomated capture and access. To chart a course for future research in ubiquitous computing, we review the accomplishments of these efforts and point to remaining research challenges. Research in ubiquitious computing implicitly requires addressing some notion of scale, whether in the number and type of devices, the physical space of distributed computing, or the number of people using a system. We posit a new area of applications research, everyday computing, focussed on scaling interaction with respect to time. Just as pushing the availiability of computing away from the traditional desktop fundamentally changes the relationship between humans and computers, providing continuous interaction moves computing from a localized tool to a constant companion. Designing for continous interaction requires addressing interruption and reumption of intreaction, representing passages of time and providing associative storage models. Inherent in all of these interaction themes are difficult issues in the social implications of ubiquitous computing and the challenges of evaluating> ubiquitious computing research. Although cumulative experience points to lessons in privacy, security, visibility, and control, there are no simple guidelines for steering research efforts. Akin to any efforts involving new technologies, evaluation strategies form a spectrum from technology feasibility efforts to long-term use studies—but a user-centric perspective is always possible and necessary

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Charting past, present, and future research in ubiquitous computing

An intelligent automated assistant system engages with the user in an integrated, conversational manner using natural language dialog, and invokes external services when appropriate to obtain information or perform various actions. The system can be implemented using any of a number of different platforms, such as the web, email, smartphone, and the like, or any combination thereof. In one embodiment, the system is based on sets of interrelated domains and tasks, and employs additional functionally powered by external services with which the system can interact.

Intelligent Automated Assistant

Cognitive engineering

The emergent nature of structure is a crucial, but often ignored, constraint on authoring hypertexts. VIKI is a spatial hypertext system that supports the emergent qualities of structure and the abstractions that guide its creation. We have found that a visual/spatial metaphor for hypertext allows people to express the nuances of structure, especialy ambiguous, partial, or emerging structure, more easily. VIKI supports interpretation of a collected body of materials, a task that becomes increasingly important with the availability of on-line information sources. The tool's data model includes semi-structured objects, collections that provide the basis for spatial navigation, and object composites, all of which may evolve into types. A spatial parser supports this evolution and enhances user interaction with changing, visually apparent organizations.

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VIKI: spatial hypertext supporting emergent structure

Hypertext systems have traditionally focused on information management and presentation. In contrast, the Aquanet hypertext system described in this paper is designed to support knowledge structuring tasks. Aquanet is a browser-based tool that allows users to graphically represent information in order to explore its structure. In this paper, we discuss our motivations for developing Aquanet. We then describe the basic concepts underlying the tool and give an overview of the user interface. We close with some brief comments about our initial experiences with the tool in use and some of the directions we see the Aquanet research moving in the near future.

Aquanet: a hypertext tool to hold your knowledge in place

Information triage is the process of sorting through relevant materials, and organizing them to meet the needs of the task at hand. It is a practice that has become increasingly common with the advent of “at your fingertips” information resources. To explore the characteristics of information triage and its interaction with spatial hypertext, a medium we claim supports the process, we have studied subjects engaged in a time-constrained decision-making task using a large set of relevant documents. We use the study task to investigate information triage under three different conditions: one in which the participants used paper documents, and two others in which the participants used variants of VIKI, a spatial hypertext system. Our findings suggest that during information triage attentional resources are devoted to evaluating materials and organizing them, so they can be read and reread as they return to mind. Accordingly, hypertext tools to support the practice should facilitate the rapid assimilation and assessment of new material, aid in the creation and management of a fluid category structure, allow readers to track their own progress through the information, and use minimum-effort methods to promote the intelligibility of results.

Spatial hypertext and the practice of information triage

Today people typically read and annotate printed documents even if they are obtained from electronic sources like digital libraries If there is a reason for them to share these personal annotations online, they must re-enter them Given the advent of better computer support for reading and annotation, including tablet interfaces, will people ever share their personal digital ink annotations as is, or will they make substantial changes to them? What can we do to anticipate and support the transition from personal to public annotations? To investigate these questions, we performed a study to characterize and compare students' personal annotations as they read assigned papers with those they shared with each other using an online system By analyzing over 1, 700 annotations, we confirmed three hypotheses: (1) only a small fraction of annotations made while reading are directly related to those shared in discussion; (2) some types of annotations - those that consist of anchors in the text coupled with margin notes - are more apt to be the basis of public commentary than other types of annotations; and (3) personal annotations undergo dramatic changes when they are shared in discussion, both in content and in how they are anchored to the source document We then use these findings to explore ways to support the transition from personal to public annotations

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Exploring the relationship between personal and public annotations

Walden’s Paths applies the concept of hypertextual paths to the World-Wide Web. Walden’s Paths is being developed for use in the K–12 school environment. The heterogeneity of the Web coupled with the desirability of supporting the teacher-student relationship make this an interesting and challenging project. We describe the Walden’s Paths implementation, discuss the elements that affected its design and architecture, and report on our experiences with the system in use.

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Catherine C. Marshall

Papers

VIKI: spatial hypertext supporting emergent structure

Aquanet: a hypertext tool to hold your knowledge in place

Spatial hypertext and the practice of information triage

Exploring the relationship between personal and public annotations

Hypertext paths and the World-Wide Web: experiences with Walden's Paths