We argue that socio-technical systems can be understood as complex adaptive systems , that is, systems containing component sub-systems interacting such that they co-evolve. This viewpoint may allow us to understand more clearly the factors that underlie the complexities of socio-technical systems, and allows for a new approach to systems design predicated on unpredictable adaptive processes. System designers, we argue, need to seek to understand the underlying structures, drivers and nature of change within the system and of the system as a whole. This paper presents an outline of the complexity mechanisms that operate within socio-technical systems, and illustrates the concepts and system design implications by way of a case. These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Distributed software is traditionally built by connecting a set of software components using a communications abstraction. The interaction semantics provided by the abstraction is predominantly static: any programming of behavior occurs in the components or in local wrappers around those components. While autonomous behavior can be programmed over these abstractions, there is increasing awareness that static interaction models are not sufficient to capture the semantic diversity found in dynamic, evolving distributed systems. This paper presents an asynchronous, distributed and executable semantic model suitable for implementing programmable connector objects. Programs described using the semantic model can be jointly executed by a set of autonomous, distributed participants with no explicit synchronization of execution state. By removing the requirement for explicit synchronization, participants can execute independently with no requirement for centralized mediation, and the asynchrony of the model implicitly allows for potentially high latencies in distributed environments like the Internet. This combination of properties makes the model ideal for e-commerce applications.

The University of Queensland has recently established a new design-focused, studio-based computer science degree. The Bachelor of Information Environments degree augments the core courses from the University's standard CS degree with a stream of design courses and integrative studio-based projects undertaken every semester. The studio projects integrate and reinforce learning by requiring students to apply the knowledge and skills gained in other courses to open-ended real-world design projects. The studio model is based on the architectural studio and involves teamwork, collaborative learning, interactive problem solving, presentations and peer review. This paper describes the degree program, its curriculum and rationale, and reports on experiences in the first year of delivery.

In a primary backup database system, transaction processing takes place at the primary and the log records generated are propagated to the backup which uses them to reconstruct the database state at the primary. If the primary fails, the backup takes over to provide continued service. Most existing designs of primary backup database systems have concentrated on techniques to tolerate complete failures in which the entire primary fails, say due to a disaster. In multiprocessor environments, where the primary and the backup databases are partitioned across multiple computers, a more common case is a partial failure in which some database partitions fail but the system as a whole survives. Existing approaches either ignore partial failures, or require the failed database partition to be unavailable. We explore a design of the primary backup database system that uses the backup not only for disaster protection, but also for continued availability during partial failures. The approach is developed in the context of the improved optimized 2-safe strategy to transmitting logs from the primary to the backup, introduced by K. Hu et al. (1997), which combines the best features of the previously developed 1-safe and 2-safe strategies.

Remote backup systems provide database availability even in case of disasters that cause complete database failure. In a remote backup system a backup tracks the transaction processing at the primary and in the event of the primary failure takes over transaction processing without causing users to observe a breach in service. Remote backup algorithms have been developed for a variety of system architectures including the case in which primary and backup consist of multiple processors connected via multiple communication lines. A limitation of existing algorithms for such environments is that they ignore the issue of partial primary and backup failures in which one or more of the primary#backup processors fail but the system as a whole survives. This paper describes the design of a primary backup system which uses the backup to provide continued availability not only during disasters but also during partial failures. The key to the approach is a non-blocking two-phase commit protocol ad...

The paper reports on the authors' experience gained in deriving a reference model for command, control, communication, computers and intelligence (C41) architectures. The reference model addresses a dilemma faced by organisations today: choosing the right distributed object platform for domain-specific applications. In making such a choice, organisations face both technological and market uncertainty arising from the availability of multiple middleware platforms and the lack of mature distributed object solutions for specific domains. They present a general methodology to addresses both of these uncertainties. This methodology provides a basis for middleware-neutral specification of vertical domain architectures based on Reference Model Open Distributed Processing (RM-ODP). They investigate the problem of mapping such a specification onto the capabilities of commercial middleware products. To address market uncertainty, the methodology incorporates results from the field of strategic planning embraced by many large enterprises-a scenario planning technique. They have successfully applied this methodology for several large corporations in Australia, including Australian Defence Forces (ADF).

Article Free Access Share on Evolving Orbit: a process report on building locales Authors: Tim Mansfield Cooperative Research Centre for Distributed Systems Technology and School of Information Technology, The University of Queensland, St. Lucia 4072, QLD Australia Cooperative Research Centre for Distributed Systems Technology and School of Information Technology, The University of Queensland, St. Lucia 4072, QLD AustraliaView Profile , Simon Kaplan Cooperative Research Centre for Distributed Systems Technology and School of Information Technology, The University of Queensland, St. Lucia 4072, QLD Australia Cooperative Research Centre for Distributed Systems Technology and School of Information Technology, The University of Queensland, St. Lucia 4072, QLD AustraliaView Profile , Geraldine Fitzpatrick Cooperative Research Centre for Distributed Systems Technology and School of Information Technology, The University of Queensland, St. Lucia 4072, QLD Australia Cooperative Research Centre for Distributed Systems Technology and School of Information Technology, The University of Queensland, St. Lucia 4072, QLD AustraliaView Profile , Ted Phelps View Profile , Mark Fitzpatrick View Profile , Richard Taylor Cooperative Research Centre for Distributed Systems Technology and School of Information Technology, The University of Queensland, St. Lucia 4072, QLD Australia Cooperative Research Centre for Distributed Systems Technology and School of Information Technology, The University of Queensland, St. Lucia 4072, QLD AustraliaView Profile Authors Info & Claims GROUP '97: Proceedings of the international ACM SIGGROUP conference on Supporting group work: the integration challengeNovember 1997 Pages 241–250https://doi.org/10.1145/266838.266919Online:16 November 1997Publication History 42citation399DownloadsMetricsTotal Citations42Total Downloads399Last 12 Months0Last 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 SiteeReaderPDF

This case study explores the nature of work for one group of systems administrators.Their virtual work domain offered little support for collaboration and mechanisms in the physical domain were often used instead.However, the way that group members were able to make sense of their complex virtual work environment suggests a new interpretation of spatial metaphors for the design of collaborative systems.This is one based on 'place' or 'locale', and 'centres', taking into account the observation that people work in multiple social worlds simultaneously, that these social worlds provide a structuring over the work domain, and that the individual draws from this structure elements relevant to their tasks.

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The problem of change propagation in multiuser software development environments distributed across a local-area network is addressed. The program is modeled as an attributed parse tree segmented among multiple user processes and changes are modeled as subtree replacements requested asynchronously by individual users. Change propagation is then implemented using decentralized incremental evaluation of an attribute grammar that defines the static semantic properties of the programming language. Building up to our primary result, we first present algorithms that support parallel evaluation on a centralized tree in response to single edits using a singe editing cursor and multiple edits with multiple editing cursors. Then we present our algorithm for parallel evaluation on a decentralized tree. We also present a protocol to guarantee reliability of the evaluation algorithm as components of the decentralized tree become unavailable due to failures and return to availability.

Work activitieshave a highly situated nature.As a result, it is not possible to classify activities exactly, since they tend to evolve as they progress.This raises a significant problem for work support tools: how to address the trade off between active support, which requires knowledge of the activity at hand, and flexibility, which is a measure of how well a system can respond to changes in activities.We have been developing the ConversationBuilder, a support tool that is intended to provide flexible, active support for (collaborative) work activities.This paper overviews the Conversation-Builder, discusses both the kinds of support it provides and its architecture, and illustrates its use through an example.

One purported advantage of hypertext systems is the ability to move between semantically related parts of a document (or family of documents). If the document is undergoing frequent modification (for example while an author is writing a book or while a software design stored in the hypertext system is evolving) the question arises as to how to incrementally maintain semantic interconnections in the face of the modifications. The paper presents an optimal technique for the incremental maintenance of such interconnections as a document evolves. The technique, based on theories of information retrieval based on lexical affinities and theories of incremental computation, updates semantic interconnections as nodes are checked into the hypertext system (either new or as a result of an edit). Because we use the semantic weight of lexical affinities to determine which affinities are meaningful in the global context of the document, introducing a new affinity or changing the weight of an existing affinity can potentially have an effect on any node in the system. The challenge met by our algorithm is to guarantee that despite this potentially arbitrary impact, we still update link information optimally. Once established the semantic interconnections are used to allow the user to move from node to node based not on rigid connections but instead on dynamically determined semantic interrelationships among the nodes.

A novel approach is proposed for automatic generation of concurrent interpreters for formal specifications of the programming languages. It consists of a formal notation and supporting algorithms. The formal notation is called action equations, which are attribute grammars extended by the concepts of events and unification. The supporting algorithms include preprocessing algorithms to generate the interpreters and evaluation algorithms embedded in the generated interpreters. Attribute grammars are reviewed, the extension to the action equations paradigm is explained, and the synthesis of action equations with a unification strategy as a means for specifying and implementing synchronization primitives is presented. The approach is illustrated by a specification of CSP. A brief comparison to related work is included.>

We present a model of distributed program editing and algorithms for the incremental checking of static semantic properties of modules that are at once semantically interdependent and physically distributed across a number of workstations connected by a high speed network.This makes possible the synthesis of modern program development hardware --workstations on high speed networks --and modern program development software --incremental, language-based program development systems --that until now have suffered from the problem of not being able to support incremental checking across distributed modules.