Distributed Systems Group
	Arbeitsgruppe Verteilte Systeme (VSYS)

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COSM Home Page

COSM Rationale

Have a look at our publication list

The book "Elektronische Märkte im Internet" will appear in January '96 (Sorry, it's written in German)

COSM Architecture

COSM Publications

COSM People

COSM History

COSM (Common Open Service Market) startet as a research project in 1993 at the Distributed System Group, Hamburg University, Computer Science Faculty. One PhD thesis and several Masters Thesises have been involved in Design and development of the COSM infrastructure. The Project statrtet in November '93.

• The Service Representation,
• the Dynamic Invocation Interface, and
• the Generic Client

have been developed until Summer 1994 when they were deployed as basic tools for further application developement.

Several student projects aimed to further extend the COSM infrastructure either by additional value-added services or by augmenting the utilization scope of service representations. The following add-on projects may serve as examples for such works:

COSM Parts & Pieces

• The Service Representation Repository is used as a data store to manage service representations in a structured way. Queries can be placed in order to retrieve appropriate service descriptions. The repository also allows users to navigate through descriptional components of single service representations
• The Integration of Notary Services into Client/Server-Communication supports clients and servers that communicate anonymously and don't trust each other. This third-party service acts as a real notary in authenticating both parties, by certifying submitted and delivered messages, and by logging the data transferred. If one of the partners shows a malicious behaviour, the other will be enabled to call-in the trusted notary service to settle the conflict.
• Dynamic Transaction Monitors as added-value services allow human users to access several remote services in a transactional way without having configured this transaction in advance. In contrast to script-based approaches or statically bound transaction programs the DTM allows users to select new services to be accessed during a running transaction. In our Implementation we support a SAGA-like transaction model. The principle could be applied to 2PC models as well.
• COSM Agents - an extension of the COSM infrastructure to support mobile agents. Service Representations - originally desiged as data store for service descriptions - are extended to encapsulate control flow based on Petri Nets. Since service representations provide persistency and heterogeneity transparency for free they fit well to the mobile agent approach. Agents are able to migrate within the Internet, to spawn concurrently executed subagents, and to merge eventually in order to collate distinct results and deliver them back to the client.
• COSM Workflow Management further extended the mobile agent approch by assigning role annotations to Petri Net transitions in order to only allow authorized clients the execution of a remote operation. In this approach, agents act as mobile capabilities for their users and therefore coordinate their interactions with a remote server. Another advantage in the interorganizational communication scenario of electronic commerce lies in a flexible ad-hoc installation of light-weight generic client software at a user's site. Workflows can thus be established and executed in a simple way.
• COSM Service Representation Browsers allow users to examine service representations in a semantically richer way than immediate interaction with the service representation repository based on an SQL interface. The Browser is yet another added value service in the COSM environment. It supplies itself a service representation to clients. Therefore it can be used interchangeably with other services.
• The COSM Service Representation Editor & Stub Generator is a convenient tool for the interactive definition of service representations. It allows to describe a server's operational interface as well as the extension of the service representations's data schema. The Generator allows server developers to generate stubs if required. This stub type-checkes incoming operation calls at runtime and transforms parameter values from the DII the the local representations of senders and receivers.
• Service Type Substitutability in Electronic Service Markets focusses on signature and specification compatibility aspects of requested and offered service representations. In order to capture a larger share of  service semantics, types as specifications of structure can be extended by behavioural descriptions of services offered. This may involve finite automatons to define valid invocation sequences (object live cycles), pre- and postconditions, or invariants to further restrict the notion of compatiblity.