Traditionally, designers organize software system as active end-points (e.g.applications) linked by passive infrastructures (e.g.networks).Increasingly, however, networks and infrastructures are becoming active components that contribute directly to application behavior.Amongst the various problems that this presents is the question of how such active infrastructures should be programmed.We have been developing an active document management system called Placeless Documents.Its programming model is organized in terms of properties that actively contribute to the functionality and behavior of the documents to which they are attached.This paper discusses active properties and their use as a programming model for active infrastructures.We have found that active properties enable the creation of persistent, autonomous active entities in document systems, independent of specific repositories and applications, but present challenges for managing problems of composition.

Document properties are a compelling infrastructure on which to develop document management applications. A property-based approach avoids many of the problems of traditional heierarchical storage mechanisms, reflects document organizations meaningful to user tasks, provides a means to integrate the perspectives of multiple individuals and groups, and does this all within a uniform interaction framework. Document properties can reflect not only categorizations of documents and document use, but also expressions of desired system activity, such as sharing criteria, replication management, and versioning. Augmenting property-based document management systems with active properties that carry executable code enables the provision of document-based services on a property infrastructure. The combination of document properties as a uniform mechanism for document management, and active properties as a way of delivering document services, represents a new paradigm for document management infrastructures. The Placeless Documents system is an experimental prototype developed to explore this new paradigm. It is based on the seamless integration of user-specific, active properties. We present the fundamental design approach, explore the challenges and opportunities it presents, and show our architectures deals with them.

Programmable Embodied Agents are portable, wireless, interactive devices embodying specific, differentiable, interactive characteristics. They take the form of identifiable characters who reside in the physical world and interact directly with users. They can act as an out-of-band communication channel between users, as proxies for system components or other users, or in a variety of other roles. Traditionally, research into such devices has been based on costly custom hardware. In this paper, we report on our explorations of the space of physical character-based interfaces built on recently available stock consumer hardware platforms, structured around an initial framework of applications.

Most document or information management systems rely on hierarchies to organise documents (e.g. files, email messages or web bookmarks). However, the rigid structures of hierarchical schemes do not mesh well with the more fluid nature of everyday document practices. This paper describes Presto, a prototype system that allows users to organise their documents entirely in terms of the properties those documents hold for users. Properties provide a uniform mechanism for managing, coding, searching, retrieving and interacting with documents. We concentrate in particular on the challenges that property-based approaches present and the architecture we have developed to tackle them.

Traditional document systems use hierarchical filing structures as the basis for organizing, storing and retrieving documents. However, this structure is very limited in comparison with the rich and varied forms of document interaction and category management in everyday document use. Presto is a prototype document management system providing rich interaction with documents through meaningful, user-level document attributes, such as “Word file,” “published paper,” “shared with Jim,” “about Presto,” or “currently in progress” Document attributes capture the multiple different roles that a single document might play, and they allow users to rapidly reorganize their document space for the task at hand. They also provide a basis for novel document systems design and new approaches to document management and interaction. In this article, we outline the motivations behind this approach, describe the principal components of our implementation, discuss architectural consequences, and show how these support new forms of interactions with large personal document spaces.

We present an interactive system for creating pen-and-ink-style line drawings from greyscale images in which the strokes of the rendered illustration follow the features of the original image. The user, via new interaction techniques for editing a direction field, specifies an orientation for each region of the image; the computer draws oriented strokes, based on a user-specified set of example strokes, that achieve the same tone as the image via a new algorithm that compares an adaptively-blurred version of the current illustration to the target tone image. By aligning the direction field with surface orientations of the objects in the image, the user can create textures that appear attached to those objects instead of merely conveying their darkness. The result is a more compelling pen-and-ink illustration than was previously possible from 2D reference imagery. CR Categories and Subject Descriptors: I.3.3 [Computer Graphics ]: Picture/Image Generation --- Display algorithms. I.4.3 [...

This paper describes a representation for pen-and-ink illustrations that allows the creation of high-fidelity illustrations at any scale or resolution.We represent a pen-and-ink illustration as a low-resolution grey-scale image, augmented by a set of discontinuity segments, along with a stroke texture.To render an illustration at a particular scale, we first rescale the grey-scale image to the desired size and then hatch the resulting image with pen-and-ink strokes.The main technical contribution of the paper is a new reconstruction algorithm that magnifies the low-resolution image while keeping the resulting image sharp along discontinuities.

We present an interactive system for creating pen-and-ink illustrations. The system uses stroke textures—collections of strokes arranged in different patterns—to generate texture and tone. The user “paints” with a desired stroke texture to achieve a desired tone, and the computer draws all of the individual strokes.

The electronic encyclopedia exploratorium (E/sup 3/) is a vision of a future computer system-an electronic book describing how thing work. Typical articles in E/sup 3/ will describe such mechanisms as compression refrigerators, engines, telescopes, and mechanical linkages. Each article will provide simulations, three-dimensional animated graphics that the user can manipulate, laboratory areas that allow a user to modify the device or experiment with related artifacts, and a facility for asking questions and receiving customized, computer-generated English-language explanations. Some of the foundational technology is discussed, focusing on topics in artificial intelligence, graphics, and user interfaces. The initial prototype system and the technical lessons learned from it, as well as the second prototype currently under construction, are described.>