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.

Providing high availability and the ability to share data despite the weak connectivity of mobile computing raises the problem of trusting replicated data servers that may be corrupt. This is because servers must be run on portable computers, and these machines are less secure and thus less trustworthy than those traditionally used to run servers. We describe the kinds of problems one must be prepared to deal with, noting that even users of secured, non-portable computers are at risk if servers trust all authorized peers. We show that high availability through data replication on portable computers need not be mutually exclusive with various levels of data security one might want. We give three solutions to this trust problem, achieving progressively higher levels of security with progressively higher costs. 1. Introduction Several existing systems, such as Ficus [1], Lotus Notes [2], and Bayou [3, 4], address the weak connectivity characteristics of mobile computing environments by a...

Bayou's anti-entropy protocol for update propagation between weakly consistent storage replicas is based on pair-wise communication, the propagation of write operations, and a set of ordering and closure.constraints on the propagation of the writes.The simplicity of the design makes the protocol very flexible, thereby providing support for diverse networking environments and usage scenarios.It accommodates a variety of policies for when and where to propagate updates.It operates over diverse network topologies, including low-bandwidth links.It is incremental.It enables replica convergence, and updates can be propagated using floppy disks and similar transportable media.Moreover, the protocol handles replica creation and retirement in a light-weight manner.Each of these features is enabled by only one or two of the protocol's design choices, and can be independently incorporated in other systems.This paper presents the anti-entropy protocol in detail, describing the design decisions and resulting features.

Asynchronous collaboration is characterized by the degree of independence collaborators have from one another.In particular, collaborators working asynchronously typically have little need for frequent and finegrained coordination with one another, and typically do not need to be notified immediately of changes made by others to any shared artifacts they are working with.We present an infrastructure, called Bayou, designed to support the construction of asynchronous collaborative applications.Bayou provides a replicated, weakly-consistent, data storage engine to application writers.The system supports a number of mechanisms for leveraging application semantics; using these mechanisms, applications can implement complex conflict detection and resolution policies, and choose the level of consistency and stability they will see in their databases.We present a number of applications we have built or are building using the Bayou system, and examine how these take advantage of the Bayou architecture.

article Free Access Share on Managing update conflicts in Bayou, a weakly connected replicated storage system Authors: D. B. Terry Computer Science Laboratory, Xerox Palo Alto Research Center, Palo Alto, California Computer Science Laboratory, Xerox Palo Alto Research Center, Palo Alto, CaliforniaView Profile , M. M. Theimer Computer Science Laboratory, Xerox Palo Alto Research Center, Palo Alto, California Computer Science Laboratory, Xerox Palo Alto Research Center, Palo Alto, CaliforniaView Profile , Karin Petersen Computer Science Laboratory, Xerox Palo Alto Research Center, Palo Alto, California Computer Science Laboratory, Xerox Palo Alto Research Center, Palo Alto, CaliforniaView Profile , A. J. Demers Computer Science Laboratory, Xerox Palo Alto Research Center, Palo Alto, California Computer Science Laboratory, Xerox Palo Alto Research Center, Palo Alto, CaliforniaView Profile , M. J. Spreitzer Computer Science Laboratory, Xerox Palo Alto Research Center, Palo Alto, California Computer Science Laboratory, Xerox Palo Alto Research Center, Palo Alto, CaliforniaView Profile , C. H. Hauser Computer Science Laboratory, Xerox Palo Alto Research Center, Palo Alto, California Computer Science Laboratory, Xerox Palo Alto Research Center, Palo Alto, CaliforniaView Profile Authors Info & Claims ACM SIGOPS Operating Systems ReviewVolume 29Issue 5Dec. 3, 1995 pp 172–182https://doi.org/10.1145/224057.224070Online:03 December 1995Publication History 630citation5,089DownloadsMetricsTotal Citations630Total Downloads5,089Last 12 Months311Last 6 weeks48 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 SiteeReaderPDF

Article Evaluation of memory system extensions Share on Authors: Kai Li Department of Computer Science, Princeton University Department of Computer Science, Princeton UniversityView Profile , Karin Petersen Department of Computer Science, Princeton University Department of Computer Science, Princeton UniversityView Profile Authors Info & Claims ISCA '91: Proceedings of the 18th annual international symposium on Computer architectureApril 1991 Pages 84–93https://doi.org/10.1145/115952.115962Published:01 April 1991 10citation391DownloadsMetricsTotal Citations10Total Downloads391Last 12 Months3Last 6 weeks0 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