Team automata have been proposed in (Ellis, 1997) as a formal framework for modeling both the conceptual and the architectural level of groupware systems. Here we define team automata in a mathematically precise way in terms of component automata which synchronize on certain executions of actions. At the conceptual level, our model serves as a formal framework in which basic groupware notions can be rigorously defined and studied. At the architectural level, team automata can be used as building blocks in the design of groupware systems.

A team automaton is said to satisfy compositionality if its behaviour can be described in terms of the behaviour of its constituting component automata. As an initial investigation of the conditions under which team automata satisfy compositionality, we study their computations and behaviour in relation to those of their constituting component automata. We show that the construction of team automata according to certain natural types of synchronization guarantees compositionality.

Team automata are a mathematical modeling tool for capturing notions of coordination, collaboration, and cooperation. They are based upon the concept of "shared actions". In this document we explain the team automata model in the context of access control mechanisms. This demonstrates the model usage and utility for capturing information security and protection structures, and critical coordinations between these structures. Modeling spatial access mechanisms as team automata not only allows analysis and verification of certain properties, it also suggests some extensions to the usual notions of access control.

We show that team automata (TA) are well suited to model secure multicast/broadcast communication with possible packet loss. This is a consequence of the natural way in which one-to-many (one-to-all) transmissions typical of multicast (broadcast) sessions can be modelled as communications between the component automata (CA) constituting a TA. To this aim, we use TA to model an instance of the EMSS multicast protocol family. In addition, we investigate a formulation of the Generalized Non-Deducibility on Compositions (GNDC) schema in terms of TA with the aim to embed TA in this well-established analysis framework. We intend to use this new setting for the formal veri cation of security properties for stream signature protocols.

Team automata have been proposed as a formal framework for modelling both the conceptual and the architectural level of groupware systems. They are defined in terms of component automata together with an interconnection mechanism which is based on shared actions (synchronizations). Components can be combined in a loose or more tight fashion depending on which actions are to be shared, and when. The formal set-up makes it possible to distinguish between, e.g., masterslave and peer-to-peer synchronizations and to classify team automata based on the mode of synchronization. Since a team automaton can be used as a component in a higher-level team, the framework allows for the representation of hierarchical systems. As an example, using a spatial access metaphor, we will consider some access control strategies in the context of team automata.

In [30], Kleijn presented a survey of the use of team automata for the specification and analysis of phenomena from the field of computer supported cooperative work, in particular notions related to groupware systems. In this paper we present a survey of the use of team automata for the specification and analysis of some issues from the field of security.

In this paper we discuss application of caT, which extends the Trellis Petri-net-based model of document/hypertext, towards specification of Web-browsable documents that respond to their reader’s characteristics, browsing activities, use environment, and interactions with other readers. The Petri net basis provides both a graphical representation of the nodes and links in the hypertext and also an automaton-based specification of the browsing behaviors encountered by readers examining the hypertext. Providing Webbrowsable responsive hypertexts in the caT context requires consideration of the structures that might be designed in support of the application and also of the mechanism for translating from caT’s custom interfaces ’ multi-window presentation to a composite that can be viewed using a standard Web browser.

Coordinating the efforts of multiple teams working in parallel on a model is a non-trivial task. A major part of this effort is to resolve conflicts, which are only detected when the work of the separate teams is integrated. In this paper we discuss how a model can be cut into distinct packages where in parallel each of these packages is locally modified by just one of the teams. Integration of the modified packages is straightforward as we only allow local changes to a package, i.e. changes that do not propagate beyond the package and that do not cause conflicts during integration. Additionally, we show how the package structure of a model and the teams working on the packages can be (temporarily) adapted to manage the need for non-local changes. We model the teams by team automata and discuss how their possible errant behaviour, which can lead to conflicts, is restricted by our strategy of model development. Conflict As models become larger and larger, it becomes inevitable...

Abstract not found

Abstract. Companies strive to retain the knowledge about their business processes by modelling them. However, non-routine people-intensive processes, such as distributed collaboration, are hard to model due to their unpredictable nature. Often such processes involve advanced activities, such as discovery of socially coherent teams or unbiased experts, or complex coordination towards reaching a consensus. Modeling such activities requires an expressive formal representation of process context, i.e. related actors and artifacts. Existing modeling approaches do not provide the necessary level of expressiveness to capture it. We therefore propose a novel modeling approach and a graphical notation, demonstrate their applicability and expressivity via several use cases, and discuss their strengths and weaknesses. 1