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.

Research into collaborative document use often concentrates on how people share document content. However, studies of real-world document practices reveal that the structures by which document corpora are organised may also, themselves, be important sites of collaborative activity. Unfortunately, this poses a problem. When category structures are used to understand a set of documents, the manipulation of those structures can interfere with shared understanding and intelligibility of the document space.We show how this problem arises in real-world settings, using a case arising from some recent field work. We outline a solution to the customisation/intelligibility problem, and show how it has been implemented in a system for personal and workgroup document management.

Designing reusable software modules can be extremely difficult.The design must be balanced between being general enough to address the needs of a wide range of clients and being focused enough to truly satisfy the requirements of each specific client One area where it can be particularly difficult to strike this balance is in the implementation strategy of the module.The problem is that generalpurpose implementation strategies, tuned for a wide range of clients, aren't necessarily optimal for each specific client-this is especially an issue for modules that are intended to be reusable and yet provide high-performance.An examination of existing software systems shows that an increasingly important technique for handling this problem is to design the module's interface in such a way that the client can assist or participate in the selection of the module's implementation strategy.We call this approach open implementation.When designing the interface to a module that allows its clients some control over its implementation strategy, it is important to retain, as much as possible, the advantages of traditional closed implementation modules.This paper explores issues in the design of interfaces to open implementation modules.We identify key design choices, and present guidelines for deciding which choices are likely to work best in particular situations.

We present a new focus+context (fisheye) technique for visualizing and manipulating large hierarchies. Our technique assigns more display space to a portion of the hierarchy while still embedding it in the context of the entire hierarchy. The essence of this scheme is to lay out the hierarchy in a uniform way on a hyperbolic plane and map this plane onto a circular display region. This supports a smooth blending between focus and context, as well as continuous redirection of the focus. We have developed effective procedures for manipulating the focus using pointer clicks as well as interactive dragging, and for smoothly animating transitions across such manipulation. A laboratory experiment comparing the hyperbolic browser with a conventional hierarchy browser was conducted.

Article High-latency, low-bandwidth windowing in the Jupiter collaboration system Share on Authors: David A. Nichols Xerox PARC, 3333 Coyote Hill Rd., Palo Alto, CA Xerox PARC, 3333 Coyote Hill Rd., Palo Alto, CAView Profile , Pavel Curtis Xerox PARC, 3333 Coyote Hill Rd., Palo Alto, CA Xerox PARC, 3333 Coyote Hill Rd., Palo Alto, CAView Profile , Michael Dixon Xerox PARC, 3333 Coyote Hill Rd., Palo Alto, CA Xerox PARC, 3333 Coyote Hill Rd., Palo Alto, CAView Profile , John Lamping Xerox PARC, 3333 Coyote Hill Rd., Palo Alto, CA Xerox PARC, 3333 Coyote Hill Rd., Palo Alto, CAView Profile Authors Info & Claims UIST '95: Proceedings of the 8th annual ACM symposium on User interface and software technologyDecember 1995 Pages 111–120https://doi.org/10.1145/215585.215706Online:01 December 1995Publication History 99citation2,591DownloadsMetricsTotal Citations99Total Downloads2,591Last 12 Months44Last 6 weeks3 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteGet Access

We present a new focus+context (fisheye) scheme for visualizing and manipulating large hierarchies. The essence of our approach is to lay out the hierarchy uniformly on the hyperbolic plane and map this plane onto a circular display region. The projection onto the disk provides a natural mechanism for assigning more space to a portion of the hierarchy while still embedding it in a much larger context. Change of focus is accomplished by translating the structure on the hyperbolic plane, which allows a smooth transition without compromising the presentation of the context.

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The design and specification of an extensible class library presents a difficult challenge:because extensibility comes from allowing the user to override parts of the implementation, more of the internal structure must be exposed to the user than in a typical procedure library.This raises issues in both how the library is designed and how its specification is written.Specification of the CLOS Metaobject Protocol required a combination of new and existing techniques to address these issues.We present those techniques, and discuss their relation to the underlying issues."This CLOS-like syntax indicates that draw is a one argument generic function; that the argument is called button; and that this method is specialized to the class text-button.

Two new parsing algorithms for context-free phrase structure grammars are presented which perform a bounded amount of processing per word per analysis path, independently of sentence length. They are thus capable of parsing in real-time in a parallel implementation which forks processors in response to non-deterministic choice points.

We present an algorithm for lambda expression reduction that avoids any copying that could later cause duplication of work. It is optimal in the sense defined by Lévy. The basis of the algorithm is a graphical representation of the kinds of commonality that can arise from substitutions; the idea can be adapted to represent other kinds of expressions besides lambda expressions. The algorithm is also well suited to parallel implementations, consisting of a fixed set of local graph rewrite rules.

This paper describes a natural language processing system implemented at Hewlett-Packard's Computer Research Center. The system's main components are: a Generalized Phrase Structure Grammar (GPSG); a top-down parser; a logic transducer that outputs a first-order logical representation; and a "disambiguator" that uses sortal information to convert "normal-form" first-order logical expressions into the query language for HIRE, a relational database hosted in the SPHERE system. We argue that theoretical developments in GPSG syntax and in Montague semantics have specific advantages to bring to this domain of computational linguistics. The syntax and semantics of the system are totally domain-independent, and thus, in principle, highly portable. We discuss the prospects for extending domain-independence to the lexical semantics as well, and thus to the logical semantic representations.