T. R, odden and G. Blair, "CSCW and Distributed Systems: The Problem of Control," Proc. Second European Conference on CSCW, Amsterdam, September 1991, L. Bannon, M. R, obinson and K. Schmidt (eds.), pp. 49-64.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....that formerly sequentially organized tasks can sometimes be performed more efficiently in parallel as a rule of thumb on the other hand. This only holds provided that the new task is welldesigned. Attention, therefore, has also been paid to general questions of activity control, for instance by [4, 5]. Furthermore, some work has been done on the transaction support for CSCW by [6, 7] and others. A final dimension that has been studied is that of users and groups of users [8, 9] The field, however, is fairly dynamic and consensus about generically applicable operational models has not yet been ....

T. R, odden and G. Blair, "CSCW and Distributed Systems: The Problem of Control," Proc. Second European Conference on CSCW, Amsterdam, September 1991, L. Bannon, M. R, obinson and K. Schmidt (eds.), pp. 49-64.

....roles of the participants and to organise the different tasks of the cooperative work in the form of workflow , i.e. flow of works. The cooperation activity organises the articulation of 4 individual and collective actions destined for realise a common task. The cooperation is conditioned by [6]: its geographical nature: co located (hall of conference) virtually co located (video conference) distant location (e mail, ftp) its temporal nature: asynchronous communication, synchronous communication. 5. COOPERATIVE LEARNING The cooperative learning has two different ....

BLAIR (G.), RODDEN (T.). "CSCW and Distributed Systems : The Problem of Control". Rapport Universit de Lancaster, 19 pages, 1991.

....Lisboa Portugal, Tel: 351 1 3100000. Direct Line: 351 1 3100223, Fax: 351 1 3145843. E mail: fpaa,nmgg inesc.pt. that tasks flow from one individual to another while coordination introduces the requirement of interaction control. Several interaction control mechanisms have been proposed [17]: free mechanisms, that rely on the social protocols established by users and do not control the access to the medium, floorcontrol, semi formal, based on language and formal mechanisms. The user interface is responsible for mediating users with the system. The userinterface must define a public ....

T. Rodden and G. Blair. CSCW and distributed systems: the problem of control. In Proceedings of the Second European Conference on Computer Supported Cooperative Work -- ECSCW '91, Amsterdam, 1991.

....Views gain the public private characteristics of the hosting perspective. 5 Concurrency and concurrency control The support of concurrency and concurrency control as requirements for allowing multiple users interactions has a strong impact at the user level in terms of feedback and control [Rodden 91] Several strategies have been devised in order to provide better user interfaces, awareness, and responsiveness of CSCW systems using the currently available technologies. The first topic to be dealt with is parallelism, i.e. the support to multiple, simultaneous activities. We will also focus ....

T. Rodden and G. Blair. CSCW and distributed systems: the problem of control. In Proceedings of the Second European Conference on Computer Supported Cooperative Work -- ECSCW '91, Amsterdam, 1991.

....and coordination [24] 22] to information sharing. Interdependence means that, in cooperative settings, activities flow from one individual to another, while coordination introduces the requirement of managing the dependencies between activities. Several coordination mechanisms have been proposed [31], e.g. free mechanisms, that rely on the social protocols established by users and do not control the access to the medium, floorcontrol, semi formal, based on language and formal mechanisms. The multiuser interface is responsible for mediating users and the system. The multiuser interface must ....

T. Rodden and G. Blair. CSCW and Distributed Systems: The Problem of Control. In Proc. of the 2nd European Conf. on Computer Supported Cooperative Work - ECSCW '91. Amsterdam. 1991.

....that formerly sequentially organized tasks can sometimes be performed more efficiently in parallel as a rule of thumb on the other hand. This only holds provided that the new task is welldesigned. Attention, therefore, has also been paid to general questions of activity control, for instance by [4, 5]. Furthermore, some work has been done on the transaction support for CSCW by [6, 7] and others. A final dimension that has been studied is that of users and groups of users [8, 9] The field, however, is fairly dynamic and consensus about generically applicable operational models has not yet been ....

T. Rodden and G. Blair, "CSCW and Distributed Systems: The Problem of Control," Proc. Second European Conference on CSCW , Amsterdam, September 1991, L. Bannon, M. Robinson and K. Schmidt (eds.), pp. 49--64.

....CONCURRENCY CONFLICTS Management of conflicts due to concurrency is a wellresearched topic in distributed databases and parallel simulation [5,7] However, the application of concurrency control to the nuances of groupware is often neglected. While groupware researchers point to its importance [6,12,14,15,19,23], application developers typically ignore it outright, or consider concurrency control to be an issue to be remedied by some textbook approach. To set the scene, this section will review what is meant by concurrency control, and will present typical remedies to concurrency conflicts used in the ....

Rodden, T. and Blair, G. (1991) "CSCW and distributed systems: The problem of control." In Proceedings of the ECSCW European Conference on Computer Supported Cooperative Work, pp. 49-64, Amsterdam, Klewar Press.

....In these models users expect system reactions considering only his her own inputs. From the user s point of view the model is the transparency of partitioning, concurrency and failures. However, developers are requesting particular non strict models for computer supported cooperative work (CSCW) [5] where the user is aware, according to some criteria, of partitioning, concurrency and failure. 3. OOram Concepts and Tool Object Oriented Role Analysis and Modeling (Ooram) 6] is an object oriented methodology first developed at SINTEF Taskon and later refined and supported by tools [7] by ....

Tom Rodden and Gordon Blair, "CSCW and Distributed Systems: The Problem of Control", Proceeding of the Second European Conference on Computer-Supported Cooperative Work", Amsterdam, The Netherlands, September 1991

....co located systems are similar to co located systems but users can be at different locations (e.g. conference rooms) Systems that provide high bandwidth real time accessibility between users are called locally remote systems. In remote systems only minimal accessibility between users exists [13]. iv. Communication Topology: Refers to the way data flows between participants. We distinguish the following types of communication topology: N N) 1 N) N 1) M N) where (M N) 1 1) and (1 1) Table 1 comprises the organisational characteristics and the set of parameters for ....

T. Rodden and G. S. Blair, "CSCW and Distributed Systems: The Problem of Control." Groupware and Computer-Supported Cooperative Work. Editor: R. M. Backer, Morgan Kaufmann Publisher, San Mateo 1993, pp. 389-396.

....the allowable order of user actions. The control component satisfies a similar role in that it controls the possible order of actions by different participants. Traditional distributed systems view control as dealing with the problems of distribution and masking such problems from applications [25]. For instance, most distributed systems allow users to know who can access which objects but they do not allow users to know who is accessing a particular object at a particular moment. The control decisions are thus embedded into the system and hidden from the users. However, due to the dynamic ....

Rodden, T. and Blair, B. (1991) CSCW and Distributed Systems: The problem of Control. In Proceedings of the second European Conference on CSCW, (Bannon, L. Robinson, M. and Schmidt, K. eds).

....course, this is not to say that standardised consistency, failure and checkpointing management would never be useful. However, we prefer to think of such features as optimisations and consider that external management addresses the more general case. This line of thought is further elaborated in [Rodden,91] In many cases, of course, it is desirable for application programmers to have the option to simply create a group with particular attributes in the areas of, say, consistency and member failure without having to explicitly build a configuration of pieces from the group model, external managers ....

Rodden, T., and G.S. Blair. "CSCW and Distributed Systems: The Problem of Control." Proceedings of the European Conference onComputer# supported Collaborative Work (ECSCW'91), Kluwer, Amsterdam, 1991. -

....Views gain the public private characteristics of the hosting perspective. 5 Concurrency and concurrency control The support of concurrency and concurrency control as requirements for allowing multiple users interactions has a strong impact at the user level in terms of feedback and control [45]. Several strategies have been devised in order to provide better user interfaces, awareness, and responsiveness of CSCW systems using the currently available technologies. The first topic to be dealt with is parallelism, i.e. the support to multiple, simultaneous activities. We will also focus on ....

T. Rodden and G. Blair. CSCW and distributed systems: the problem of control. In Proceedings of the Second European Conference on Computer Supported Cooperative Work -- ECSCW '91, Amsterdam, 1991.

....co located systems are similar to co located systems but users can be at different locations (e.g. conference rooms) Systems which provide high bandwidth real time accessibility between users are called locally remote systems. In remote systems only minimum accessibility between users exists [63]. From Requirements to Services: MPG 95 10 16 iv. Communication Topology: Refers to the way data flows between participants. Different kinds of communication topologies can co exist in one application. We distinguish the following types of communication topology: N N) 1 N) N 1) M N) ....

T. Rodden and G. S. Blair: "CSCW and Distributed Systems: The Problem of Control." Groupware and Computer-Supported Cooperative Work. Editor: R. M. Backer, Morgan Kaufmann Publisher , San Mateo , 1993, pp. 389-396.

....possible to achieve Is it worthwhile Nevertheless, if transparency exists, developers need not concern themselves with distribution issues, since the platform hides them. Despite obvious advantages, transparency has some drawbacks: absence of detail and lack of support for non traditional models [4]. In most systems, transparency does not allow distributed issues to be handled at different levels of abstraction and according to particular application needs. Moreover, only traditional application models are supported by such systems. It is hard to support new emerging areas, such as ....

....Consistency, Isolation, Durability) 3 . This models are built upon non strict computationalmodels inherent to distributed systems, e.g. a communication delay can generate replicas with different values. Recently, developers are requesting particular non strict models for cooperative work [4] in which user control and synergistic cooperation [9, 10] are needed. These models fulfill application semantics and we refer to them as non strict application models by opposition to non strict computational models. Since non strict application models are still an open research area, no general ....

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Tom Rodden and Gordon Blair. CSCW and Distributed Systems: The Problem of Control. In Proceeding of the Second European Conference on Computer-Supported Cooperative Work, pages 49-- 63, Amsterdam, The Netherlands, September 1991.

....is done in a concurrent and distributed environment. However, application functionalities implementation is usually independent of distribution issues and could be tested and debugged in a amicable centralized and non concurrent environment. Computer supported cooperative work (CSCW) researchers [Rodden 91] identified some drawbacks in distributed technology: ffl Absence of detail. Transparency does not allow distribution issues to be handled at different levels of abstraction and according to particular application needs. ffl Lack of support for non traditional models. Only traditional models are ....

....and data are isolated. In these models users expect system reaction considering only his her own inputs, from the user s pointof view the model is the transparency of partitioning, concurrency and failures. However, developers are requesting particular non strict models for cooperative work [Rodden 91] where the user is aware, according to some criteria, of partitioning, concurrency and failure. The DASCo approach also identifies in the solution space a set of distribution concerns. The solution concerns considered in this paper and associated with the partitioning problem are: replication, ....

Tom Rodden and Gordon Blair. CSCW and Distributed Systems: The Problem of Control. In Proceeding of the Second European Conference on Computer-Supported Cooperative Work, pages 49--63, Amsterdam, The Netherlands, September 1991.

....The other approach, we refer to as the distributed systems approach, consists of providing a distributed cooperation layer based on system support (i.e network, OS) thus separating the user interface (UI) issues from the distributed interaction aspects. Some work exists relating both approaches [45] and the next section develops in more detail the various aspects of the type of support that can be provided. ffl Supported applications: second, we can differentiate the cases where the platform supports sharing of already existing single user applications and or the development of new ....

T. Rodden and G. Blair. Cscw and distributed systems: The problem of control. In Proceedings of the Second European Conference on Computer-Supported Cooperative Work, pages 49--64, September 1991.

....for the cooperative activity and makes the system more complex. However, in certain circumstances , applications may need to be aware of what is going on. Given the flexibility of CSCW systems is important that the concept of selective transparency is applied within cooperative environments [Rodden 91] and that the degree of transparency can be selected and modified. A number of different transparencies are important to the development of a cooperative environment. The transparencies central to the development of an open cooperative environment are briefly listed in the table over: 1 This is ....

Rodden T., Blair G., ` CSCW and Distributed Systems: The Problem of Control' in proceedings of ECSCW'91,Amsterdam, 25-27th September 1991, Kluwer.

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Rodden, T., Blair, G.S., (1991) "CSCW and Distributed Systems: The Problem of Control", Proceedings of the European Conference on Computer Supported Cooperative Work (ECSCW'91),Kluwer, Amsterdam, 1991.

....Rooms Conferencing Message Systems Co Authoring KEY Figure 1: A Classification space for CSCW systems This classification space shown in figure 1 shows how CSCW system can be classified depending on two major characteristics. A further characteristic common to all cooperative systems is control [Rodden 91] Two predominant control mechanisms have emerged within CSCW systems, speech act theory systems and procedure based systems. Both these forms of control are discussed in more depth in appendix A. 3. Message systems Cooperative message systems are often termed structured or active message systems ....

Rodden T., Blair G., ` CSCW and Distributed Systems: The Problem of Control' in proceedings of ECSCW'91,Amsterdam, 2527th September 1991.

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Rodden, T., Blair, G.S. (1991): "CSCW and Distributed Systems: The Problem of Control." in L.

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#3#:349#368, 1991. #20# T. Rodden and G. Blair. CSCW and distributed systems: the problem of control. In Proceedings of the Second European Conference on Computer SupportedCooperative Work # ECSCW '91, Amsterdam,

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T.Rodden, G. Blair: "CSCW and Distributed Systems: The Problem of Control", Proc. of the ECSCW'91. (1991)

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Tom Rodden, Gordon S. Blair, "CSCW and Distributed Systems: The Problem of Control", Proc. of the ECSCW'91, Amsterdam, September, 1991

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Rodden, T., and G. Blair. "CSCW and Distributed Systems: The Problem of Control." Second European Conference onComputer-Supported# Cooperative Work (ECSCW '91), Amsterdam, The Netherlands, September 25-27, 1991. Pages: 20 64.

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Rodden, T., and G. Blair. "CSCW and Distributed Systems: The Problem of Control" Second European Conferenceon# Computer-Supported Cooperative Work (ECSCW '91), Amsterdam, The Netherlands,September# 25-27, 1991. Pages: 49-64.

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