Deontik is an active participant and contributor in scientific research relating to our specialties. This includes the work on
GPipe: Using Adaptive Directed Acyclic Graphs to Run Data and Feature Pipelines with on-the-fly Transformations
Advances in Complex Decision Making 2024: 21-37
Chapman and Hall/CRC, 2024 PDF
Enacting policies in digital health: A case for smart legal contracts and distributed ledgers?
The Knowledge Engineering Review, 35
Cambridge University Press, February 2020 Abstract
This paper presents an approach for the enactment of policies in digital health based on our earlier work on the implementation of digital contracts in distributed systems. A formal policy model and an abstract policy language for the expression of healthcare policies are first proposed, leveraging the semantics of the ISO Reference Model for Open Distributed Processing enterprise language standard. Healthcare consent policies included in the HL7 Fast Health Interoperability Resource (FHIR®) standard are used to illustrate the modelling approach. Several distributed ledger and smart legal contract options were considered next as target platforms for implementation. Their benefits are highlighted along with considerations on their use reflecting business concerns of risk, trust and cost.
On legal contracts, imperative and declarative smart contracts, and blockchain systems
Artif. Intell. Law 26(4): 377-409 (2018)
Elseveir, December 2018 PDF
Specifying and building interoperable eHealth systems: ODP benefits and lessons learned
Computer Standards & Interfaces, special issue on Open Distributed Systems, April 2012
Elseveir, 2012 Abstract
This paper describes the experiences of Australia’s National E-Health Transition Authority in using the RM-ODP to address a number of interoperability challenges in Australian eHealth. The RM-ODP viewpoints provide the separation of concerns across a specification, allowing direct support of independent capability levels within an eHealth community. The RM-ODP provides precise architectural expression, including that of business and policy contexts critical for eHealth. This precision is important for a tools-based architectural approach that supports traceability between requirements, design and implementation. The paper identifies some issues encountered while using the RM-ODP, which provide input into further standardisation efforts.
Foreword to the Special Issue on Enterprise Services Computing and Industrial Applications (Guest Editorial)
IEEE Transactions on Systems, Man, and Cybernetics, Part C 38(3), 277-279 (2008)
IEEE, 2008 PDF
Introduction to the Special Issue: Electronic Contract Architectures and Languages
Int. J. Electronic Commerce 12(4): 5-8 (2008)
World Scientific, December 2008
Enterprise distributed computing (guest editorial)
International Journal of Cooperative Information Systems (IJCIS), Vol 15, No 4
IEEE, December 2006
A formal analysis of a business contract language
International Journal of Cooperative Information Systems (IJCIS), special issue on Enterprise Distributed Computing, Vol 15, No 4,
World Scientific, December 2006 PDF
Topics in Contract Architecture and Languages (guest editorial)
International Journal of Cooperative Information Systems (IJCIS), special issue on Contract Architecture and Languages Vol 14, Nos. 2 & 3
Wold Scientific, Jun & Sep 2005
Extending choreography with business contract constraints
International Journal of Cooperative Information Systems, Vol 14, Num 2&3
World Scientific, June & September 2005 PDF Abstract
Business contracts play a central role in governing commercial interactions between organizations. It is increasingly recognized that business contract conditions need to be closely linked to internal and external business processes, both to reduce the risk of contract violations and to ensure compliance with legislative regimes. Recent research has proposed contract languages allowing the specification of obligations, permissions and prohibitions in business contracts. Business processes that cross-organizational boundaries can be specified in choreography and coordination languages but these do not provide appropriate abstractions for contract constraints. In this paper, we examine the transformation of contract constraints in a business contract language into expressions in a choreography language. An example cross-organizational process is presented, along with a specification of the process in a choreography language and a specification of a set of contract conditions for the process in a business contract language. The contract terms are then translated into choreography expressions that govern the process to ensure compliance. Subsequent discussion explores a number of business and technology issues related to the results. We conclude that cross-organizational business processes can be monitored and enforced according to business contract specifications through the transformation of a contract definition to constraints on process behavior.
Special Issue on Contract Architecture and Languages (Guest Editorial)
Int. J. Cooperative Inf. Syst. 14(2-3): 73-76 (2005)
World Scientific, December 2005 PDF
A unified behavioural model and a contract language for extended enterprise
Data Knowledge Engineering 51(1), pp. 5-29
Elsevier, March 2004 PDF Abstract
This paper presents a coordination model for expressing behaviour in an extended enterprise. Our model is unified because it enables the same style of expressions for describing behaviour/structure in a selfcontained enterprise and for describing cross-enterprise behaviour/structure. This model can support a broad range of modelling activities but the specific focus of this paper is on deriving the key elements of a domain language primarily targeted at expressing and monitoring behavioural conditions stated in business contracts. We also show how business contracts serve as a unifying mechanism for describing interactions in the extended enterprise.
Describing Open Distributed Systems: A Foundation
The Computer Journal, Vol 40, Num 8
British Computer Society, 1997 PDF Abstract
In this paper we outline a semantic model for open distributed systems which provides a foundation for a corresponding architecture description language. This semantic model is based on architecture models reported in [2][5], with a number of refinements to support abstraction and composition. The model is specifically designed to describe open distributed systems independent of implementation details such as communication protocols and middleware systems. The modelling concepts in the semantic model are: object (a model of an entity), event (a unit of interaction between an object and its environment), event relationship (a specification of behaviour defining the relationships amongst a set of events), interface (an abstraction of an object’s interaction with its environment) and binding (a context for interaction between objects). The binding concept is particularly important because it can describe any kind of interaction in an open distributed system, ranging from remote procedure calls and multicast to more complex,enterprise interactions. Special attention is given to the problem of composition and abstraction of events and behaviour in the model. This is needed to reflect the reuse, evolution and interworking requirements of open distributed systems. Our approach allows for the effective modelling of asynchrony,concurrency and complex flows of information in open distributed systems.
An application-level implementation of causal timestamps and causal ordering
Distributed Systems Engineering
IOP Publishing, June 1995 PDF Abstract
Maintenance of causality information in distributed systems has previously been implemented in the communications infrastructure with the focus on providing reliability and availability for distributed services. While this approach has a number of advantages, moving causality information up into the view and control of the application programmer is useful, and in some cases, preferable. In an experiment at the University of Queensland, libraries to support application-level maintenance of causality information have been implemented. The libraries allow the collection and use of causality information under programmer control, supplying a basis for making causal dependency information available for application management and troubleshooting. The libraries are also unique in supporting existing distributed systems based on the remote procedure call paradigm. This paper describes the underlying theory of causality, and the design and implementation of the libraries. An event reporting service example is used to motivate the approach, and a number of previously unresolved practical problems are addressed in the design process.
DYN2 Method For Optimal Real-Time Control of Water Flow in Open Channels
Journal of Irrigation & Drainage Div., Dec. 1989
American Society for Civil Engineers (ASCE), 1989
Describing and Supporting Complex Interactions in Distributed Systems
The University of Queensland, July 2001 PDF
The idea of building software that spans many computers has been a significant driver for research since the earliest days of computing. Despite this past effort, there are still considerable resources being applied to the problems of building distributed software systems. This thesis proposes an alternative approach to building distributed systems that is both pragmatic and has a sound theoretical basis. The approach is driven by the following key assertions:
Given this context, this thesis describes Finesse, a system for describing and supporting the complex interactions of components in distributed applications. Finesse uses the notion of event relationships to describe the visible behaviour of components and how those behaviours are coordinated to satisfy the requirements of an application. There are three significant aspects of Finesse, each of which makes a novel contribution to the body of research:
The system implies a mediated communication architecture, where a mediating component accepts events from components and distributes appropriate notifications to other components. This decoupling of components and the mediation semantics allow the necessary transformation of data and event correlation to support legacy applications. The event relationship semantics, however, also allow the mediator to be fully distributed and asynchronous. This asynchrony allows us to deal with high-latency, high-failure communication networks. The design of the programming language allows us to develop mediating ’components’ that can be nested within a higher level mediator, thus giving us the ability to build a flexible library of abstractions for relationships between participating components.
The thesis includes a set of examples that demonstrate the approach and its strengths. Through the examples and the arguments expressed in the work, this thesis demonstrates the power and utility of the event relationship approach to building distributed systems.
Enterprise Aspects of Open Distributed Systems
The University of Queensland, May 1996 PDF
This thesis explores new enterprise characteristics and requirements of emerging computing and telecommunications systems: the economic and business aspects of open distributed systems (ODSs). We analyse the interplay of technological and commercial trends pertinent to ODSs and identify those enterprise factors which attract special attention from the end-user, management and technical communities involved. Relevant paradigms from economics and business are selected; it is then illustrated how they can be applied to related problems in ODSs.
Two specific concepts are investigated: i) the enterprise notion of Quality of Service (QoS) and ii) new types of uncertainty inherent in a large class of services in ODSs. The aim of the former is to develop a generic, user oriented and service independent methodology which will facilitate the description and measuring of QoS in ODSs. We present a methodology which is based on the use of a specific economic theory and relevant results from market research and psychology. The objective of the latter is to address possible economic inefficiency due to uncertainty which can arise from the properties inherent in ODSs: participating parties have different characteristics, objectives and requirements, they can belong to different geographical, organisational or other domains, and yet share computing and communication resources. We address this problem from both a theoretical and a practical angle. The theoretical enquiry emanates from economic agency theory, which can be used to design efficient contracts in the presence of uncertainty. The practical approach is based on business and legal ways of handling the uncertainty associated with the interactions of economic actors in the real world: namely, the use of contracts. We derive a business contract architecture, which can facilitate business dealings in ODSs. It is based on notions of contracts drawn from economic, legal and business perspectives.
Following these theoretical and architectural researches, we present a partial implementation of the business contract architecture to demonstrate the feasibility of our approach.
Computable Consent–From Regulatory, Legislative, and Organizational Policies to Security Policies
EDOC Conference 2022: 3-18
Springer, 2022 PDF
An open architecture for complex event processing with machine learning
EDOC Conference 2020: 51-56
IEEE, 2020 PDF
Ethics in Digital Health: a deontic accountability framework
EDOC19 Proceedings
IEEE, October 2019 PDF Abstract
We present key ethics concerns in digital health and introduce related ethics principles to address these concerns. We propose mappings of these principles into deontic logic concepts to support ethics-based analysis. This provides input into detailed design of deontic and accountability constraints using semantic foundation from the ODP enterprise language standard [1]. We refer to our approach as ‘ethics by design’ because it aims at explicit inclusion of ethics principles into contemporary software development and tooling. The paper is focused on digital health, but the approach has broader applicability.
An Event-Based Model to Support Distributed Real-Time Analytics: Finance Case Study
Enterprise Distributed Object Computing
IEEE, September 2015 PDF
Real-time analytics for legacy data streams in health: Monitoring health data quality
Enterprise Distributed Object Computing
IEEE, September 2013 PDF Abstract
Healthcare organizations are increasingly using information technology to ensure patient safety, increase effectiveness and improve efficiency of healthcare delivery. While the use of health information technology (HIT) has realized many improvements, it has also introduced new failure modes arising from data quality and IT system usability issues. This paper presents an approach towards addressing these failure modes by applying real-time analytics to existing streams of clinical messages exchanged by HIT systems. We use complex event processing provided by the EventSwarm software framework to monitor data quality in such systems through intercepting messages and applying rules reflecting the syndromic surveillance model proposed in [4]. We believe this is the first work reporting on the real-time application of syndromic surveillance rules to legacy clinical data streams. Our design and implementation demonstrates the feasibility of this approach and highlights benefits obtained through improved operational quality of HIT systems, notably better patient safety, reduced risks in healthcare delivery and potentially reduced costs.
Open Distributed Coordination with Finesse
Proceedings SAC 1998
IEEE, September 2013 PDF Abstract
Coordination languages have recently been attracting significant attention as a means of programming parallel and distributed systems. The approach of separating coordination from computation is particularly attractive in distributed systems because there are a wide range of possible interaction, quality and reliability semantics that are either hidden or ignored by traditional infrastructures based on remote procedure call. Introducing an explicit, programmable model for the distributed infrastructure makes these semantics visible and tractable, without requiring substantial changes in distributed components. This paper presents Finesse, a language for describing the interaction of components in open distributed systems, and demonstrates its power through a number of examples.
Linking contracts, processes and services: an event-driven approach
IEEE International Conference on Services Computing (SCC 2006)
IEEE, September 2006 PDF
Translating business contract into compliant business processes
EDOC06 Proceedings
IEEE, September 2006 PDF
Compliance checking between business processes and business contracts
EDOC06 Proceedings
IEEE, September 2006 PDF Abstract
It is a typical scenario that many organisations have their business processes specified independently of their business contracts. This is because of the lack of guidelines and tools that facilitate derivation of processes from contracts but also because of the traditional mindset of treating contracts separately from business processes. This paper provides a solution to one specific problem that arises from this situation, namely the lack of mechanisms to check whether business processes are compliant with business contracts. The central part of the paper is logic based formalism for describing both the semantics of contract and the semantics of compliance checking procedures.
Towards a methodology for deriving contract-compliant business processes
BPM2006 Proceedings
September 2006 PDF
Policy-rich multi-agent support for E-health applications
Proc IFIP I3E conference (E-commerce, E-Business, E-Government)
IFIP, September 2005 PDF
Dealing with contract violations: formalism and domain specific language
EDOC05 Proceedings
IEEE, September 2005 PDF
Towards Integrating Business Policies with Business Processes
BPM05 Proceedings
IEEE, September 2005 PDF Abstract
One limitation of current business process (BP) initiatives, e.g. [1, 2, 3], is their lack of positioning of BP models within a broader enterprise model covering organisational structures, policies and contracts. This paper partly addresses this limitation by applying our community model [4] to a behavioural style typical of BP approaches. The aim of the paper is to augment BPs with policy expressions to support monitoring of participants’ behaviour against agreed policies. Section 2 introduces key concepts from ebXML’s BP specification (ebBP) [1] and BP modelling notation (BPMN) [3] of relevance for business policies, and illustrate them with a simple example (Fig. 1). Section 3 introduces our policy concepts and maps them onto the relevant BPMN and ebBP concepts. Section 4 discusses open issues and future work.
Elemental and Pegamento: the Final Cut – Applying the MDA pattern
EDOC04 Proceedings
IEEE, September 2004 PDF
Inter-organisational collaborations supported by e-contracts
Proc IFIP I3E conference (E-commerce, E-Business, E-Government)
IFIP, September 2004 PDF
Identifying requirements for business contract language
EDOC2003 Proceedings
IEEE, September 2003 PDF
Conversation-oriented Protocols for Contract Negotiations
EDOC2003 Proceedings
IEEE, September 2003 PDF
Contract Performance Assessment for Secure and Dynamic Virtual Collaborations
EDOC2003 Proceedings
IEEE, September 2003 PDF
On Expressing and Monitoring Behaviour in Contracts
EDOC02 Proceedings
IEEE, September 2002 PDF Abstract
This paper addresses the problem of transforming natural language descriptions of contracts into a form that is suitable for automating various contract management functions. We investigate two complementary methods that can be used to achieve this. One method is suitable for the contract specification phase – to specify expected behaviour of contracting parties so that they can satisfy policies stated in a contract. This method also allows for checking aspects of contract consistency as well as flexible integration of internal organisational policies with the contract policies. Another method targets the contact run-time phase – for monitoring behaviour of parties to the contract and other aspects of contract performance. When combined, these two methods provide a basis to support an increasing level of automation of many mundane contract activities, while allowing humans to be involved in ultimate decision making.
Architecting Cross-Organisational B2B Interactions
EDOC01 Proceedings
IEEE, September 2001
A Distributed Asynchronous Execution Semantics for Programming the Middleware Machine
Proceedings ISADS 2001
IEEE, 2001 Abstract
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.
Author Obliged to Submit Paper before 4 July: Policies in an Enterprise Specification
Proceedings Policy01 workshop
IEEE, September 2001 PDF Abstract
Specifying policies doesn’t occur in splendid isolation but as part of refining an enterprise specification. The roles, the tasks, and the business processes of an ODP community provide the basic alphabet over which we write our policies. We illustrate this through exploring a conference programme committee case study. We discuss how we might formulate policies and show how policies are refined alongside the refinement of the overall system specification, developing notions of sufficiency and necessity. Policy delegation is also discussed and we categorise different forms of delegating an obligation.
Figaro Should Be in Sydney by the 2nd of July - Contracting in Many-To-Many e-Services
Proc IFIP I3E conference (E-commerce, E-Business, E-Government)
IFIP, September 2001 PDF
Mapping Enterprise Roles to CORBA Objects Using Trader
International IFIP/GI Working Conference on a Universal Service Market USM 2000: Trends in Distributed Systems: Towards a Universal Service
Springer, September 2000 PDF
Processes, Roles, and Events: UML Concepts for Enterprise Architecture
UML2000 Proceedings
IEEE, September 2000 PDF Abstract
This paper presents an integrated approach for modelling enterprise architectures using UML. To satisfy a need for a wide range of modelling choices, we provide a rich set of process-based and role-based modelling concepts, together with a flexible way of associating business events with business processes and roles. Our approach enriches Unified Modelling Language (UML) to support the requirements of enterprise distributed object computing (EDOC) systems and is currently being considered by the Object Management Group (OMG) for standardisation.
Policies in Communities: Extending the ODP Enterprise Viewpoint
EDO98 Proceedings
IEEE, September 1998 PDF Abstract
The Reference Model of Open Distributed Processing (RM-ODP) introduces the notion of an enterprise viewpoint and provides a minimum set of concepts for structuring enterprise language specifications. This paper extends the RM-ODP enterprise concepts by exploring how policy can be modelled within and between communities. A model for enterprise behaviour based on physical and social actions is presented.
Inter-enterprise contract architecture for open distributed systems: security requirements
WETICE2006 Proceedings
September 1996 PDF
An Improved Model for Transactional Operations in RM-ODP
Proc ICODP'93, 1993.
IEEE, 1993
On Some Performance Issues for Open Services Support in Future Networks
Proc ICC'93 conference
IEEE, September 1993
Some New Performance issuesConsierations in Open Distributed Environments
Proc ICC'93 conference
IEEE, September 1993
Some Considerations on the Distribution of IN Functions for Supporting the UPT Service
Seventh Australian Teletraffic Research Seminar
IEEE, September 1992
The Service Interactions Problem In Future Networks
Sixth Australian Teletraffic Research Seminar
September 1991
Implementation of SCADA Functions at HMS Strezevo
ETAN conference
September 1988
Optimal Real-Time Control of Water Transport in Open Channels
Proc. Sympois97
September 1987
Enabling scalable AI for Digital Health: interoperability, consent and ethics support
EDOC Workshop Proc. 2021: 18-27
IEEE, 2021 PDF
Towards model-driven expressions of the blockchain ethical design framework
SDLT19 Proceedings
Griffith University, December 2019 Abstract
This paper investigates model-driven extensions of the blockchain ethical design framework developed by Laponte and Fishbane [1]. The extensions are motivated by our recent proposal to provide a model-driven approach to expressing ethics principles and ethics concepts in digital health, including new privacy and AI challenges [2]. Our model-driven approach is based on the precise modelling concepts from the ISO ODP Enterprise Language standard [3]. The combination of the intentional design approach from the blockchain ethical design framework and the precise modelling concepts for expressing the enterprise aspects of distributed systems, including governance, accountability and privacy, provides a sound foundation for a tool-based design and deployment of responsible distributed ledger solutions.
Towards digitalisation of healthcare policies: case for smart legal contracts?
SDLT18 Proceedings
Griffith University, November 2018 PDF Abstract
We present an approach for the digitalisation of healthcare policies based on our work on the formalisation and implementation of digital contracts. An abstract policy language is proposed leveraging the semantics of the RM- ODP enterprise language standard and augmented with the latest research in deontic logic. Several digital contract languages, considered as ledger agnostic smart legal contract languages, are identified as candidates to implement this policy language. We use healthcare consent policies included in the HL7 FHIR consent resource to test our approach.
Towards a Workflow-Centric, Context Aware Clinical Application Framework
Health Informatics Conference (HIC) 2017
HISA Australia, 2017 PDF Abstract
We outline an approach for implementing application support for clinical workflow that is aware of dynamic context of healthcare delivery. This context captures patient specific information, previous and future activities of clinicians involved in patient healthcare and supports clinicians’ cognitive models. This application framework leverages some of the concepts and models that have been used to formalize a major, multidisciplinary clinical workflow redesign project at a major US hospital. We present our results and future work.
Influence of Parallelism Property of Streaming Engines on Their Performance
ADBIS (Short Papers and Workshops) 2016: 104-111
IEEE, 2016
Towards Better Semantics for Services in eHealth Standards: A Reference Ontology Approach
EDOC Workshops 2014: 276-285
IEEE, 2014 PDF
Addressing interoperability in e-health: an Australian approach
EDOC06 Proceedings
IEEE, September 2006 PDF Abstract
This paper describes the use of the ISO ODP family of standards to address interoperability issues in the Australian e-health environment. The Australian health system has a specific institutional structure and funding model involving a combination of federal, state, territory and local government jurisdictions along with the private sector. This arrangement requires a thorough understanding of legislation, regulation and other policies, as well as governance models and the collaborative nature of healthcare businesses to inform the building of interoperable and sustainable IT systems. The aim is to provide better, safer and more efficient service delivery than what current silo-based approaches deliver. The ODP standards provide a valuable conceptual basis for addressing diversity, richness and evolvability of such a complex system, embracing both human actors and IT systems. The ODP Enterprise Language provides core concepts for describing the organisational context for e-health systems, while the ODP-RM architecture framework allows for the description of various e-health stakeholders’ concerns, from organisational, information and technical perspectives. Further value of the standard comes from rigorous conformance and compliance guidelines
An Approach for Validating BCL Contract Specifications
Enterprise Distributed Object Computing, Contract Architectures and Languages Workshop (CoALa2005)
IEEE, September 2005 PDF
Generic model for services: health domain study
EDOC05 Proceedings, Workshop on ODP for Enterprise Computing (WODPEC05)
IEEE, September 2005 PDF
On the mapping of business contracts to executable choreography
Enterprise Distributed Object Computing
IEEE, September 2004 PDF
On design and implementation of a contract monitoring facility
IEEE Conference on Electronic Commerce, the 1st IEEE Workshop on Electronic Contracting (WEC04)
IEEE, December 2004 PDF
B2B Contract Implementation using Windows DNA
Information Technology for Virtual Enterprise workshop, Australian Computer Science Week
IEEE, January 2001 PDF
Extending Support for Contracts in ebXML
Information Technology for Virtual Enterprise workshop, Australian Computer Science Week
IEEE, January 2001 PDF
Business Contracts for B2B
CAiSE 2000 Workshop - Infrastructure for Dynamic Business-to-Business Service Outsourcing (ISDO 2000)
IEEE, 2000 PDF
Use of Roles and Policies for Specifying, and Managing a Virtual Enterprise
Proc. Ninth Int. Workshop on Research Issues on Data Engineering - Information Technology for Virtual Enterprises. RIDE-VE'99
IEEE, September 1999 PDF
Language Support for Distribution in CSCW Systems
ECSCW'97 Workshop on Object-Oriented Groupware Platforms
IEEE, PDF
Orbit - Supporting social worlds Human-Computer Interaction
INTERACT'97
IEEE, July 1997
A Panacea for Distributed CSCW Infrastructure.
OzCHI'96 Workshop on the Next Generation of CSCW Systems
IEEE, 1996 PDF
A Type Model Supporting Interoperability in Open Distributed Systems.
Proc of TINA'95, 1995
Sep 1995
New types of resource issues in open distributed systems: an agency theory modelling approach
Third International Conference on Telecommunication Systems Modelling and Analysis
IEEE, September 1995 PDF
An Architecture for Supporting Business Contracts in Open Distributed Systems
IEEE, 1995
Enhancing Communication and Cooperation in Human Service Delivery Through the Internet
IEEE, 1995 PDF
An Introduction to Open Distributed Processing.
Proc of the ACS Queensland Branch Conference
ACS, Sep 1993
New Economic-driven Aspects of the ODP Enterprise Specification and Related Quality of Service Issues
Third International Conference on Telecommunication Systems Modelling and Analysis
IEEE, September 1993