Lars Michael Kristensen

Lars Michael Kristensen
Høgskulen på Vestlandet | HVL · Department of Computing, Mathematics and Physics

PhD

About

136
Publications
11,377
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
5,047
Citations
Citations since 2017
4 Research Items
1573 Citations
2017201820192020202120222023050100150200250300
2017201820192020202120222023050100150200250300
2017201820192020202120222023050100150200250300
2017201820192020202120222023050100150200250300

Publications

Publications (136)
Article
The high and dense representation of wooden homes in Norway, combined with periods of dry and cold climate during the winter season resulting in very dry indoor conditions, have historically resulted in severe fires. Thus, it is important to have an accurate estimate of the current and near future fire risk to take proper planning precautions. Clou...
Conference Paper
In this paper, we provide a foundation for the definition and composition of multilevel domain-specific modelling languages. We will introduce modularization techniques such as composition, aggregation and referencing to enhance flexibility and reusability of these languages. To explain this foundation, we use Coloured Petri Nets (CPN) as a paradig...
Conference Paper
Full-text available
Distributed systems modelling often involves a set of heterogeneous models where each model specifies a set of local constraints capturing a specific view of the system. In real life, distributed systems are often loosely connected and interdependencies are not defined into their software models. This limits the scope of optimization of distributed...
Article
Full-text available
The increased application of wireless technologies including Wireless Sensor Actuator Networks (WSAN) in industry has given rise to a plethora of protocol designs. These designs target metrics ranging from energy efficiency to real-time constraints. Protocol design typically starts with a requirements specification, and continues with analytic and...
Conference Paper
Full-text available
Epistemic logic plays an important role in artificial intelligence for reasoning about multi-agent systems. Current approaches for modelling multi-agent systems with epistemic logic use Kripke semantics where the knowledge base of an agent is represented using atomic propositions, but intelligent agents need to be equipped with formulas to derive i...
Article
Full-text available
Domain specific modelling languages reduce the effort required to specify systems by providing higher level abstractions. Although this is a promising approach for reducing the complexity of system specifications, creating a new domain specific modelling language is a complex task. WebDPF is a web-based metamodelling tool that aims to reduce the ef...
Chapter
Full-text available
Pragmatics Annotated Coloured Petri Nets (PA-CPNs) are a restricted class of Coloured Petri Nets (CPNs) developed to support automated generation of protocol software. The practical application of PA-CPNs and the supporting PetriCode software tool have been discussed and evaluated in earlier papers already. The contribution of this paper is to give...
Conference Paper
TinyOS is a widely used platform for the development of networked embedded systems offering a programming model targeting resource constrained devices. We present a semi-automatic software engineering approach where Coloured Petri Net (CPNs) models are used as a starting point for developing protocol software for the TinyOS platform. The approach c...
Conference Paper
Full-text available
Metamodelling and model transformation play important roles in model-driven engineering as they can be used to define domain-specific modelling languages. During the modelling phase, modellers encode domain knowledge into models which may include both structural and behavioral aspects of a system. The contribution of this paper is a new web-based m...
Conference Paper
Full-text available
Model Driven Engineering (MDE) uses formal methods to build mathematically rigorous models of complex systems. Metamodelling plays an important role in MDE as it is used to specify domain specific modelling languages. However, the potential of metamodelling has not been fully explored. Current approaches of MDE are often at a low level of abstracti...
Conference Paper
Full-text available
Metamodelling plays an important role in model-driven engineering as it can be used to define domain-specific modelling languages. During the modelling phase, software designers encode domain knowledge into models which may include both structural and behavioural aspects of a system. In this paper we propose a diagrammatic approach to aid the softw...
Article
The vast majority of IT systems today can be characterized as concurrent and distributed in that their operation inherently relies on communication, synchronization, and resource sharing between concurrently executing software components and applications. Colored Petri Nets, or CPNs, combine Petri nets with a programming language to obtain a scalab...
Conference Paper
In earlier work, we have proposed the Dual-Mode Adaptive MAC (DMAMAC) protocol relying on a combination of Time Division Multiple Access (TDMA) and Carrier Sense Multiple Access (CSMA). The DMAMAC protocol is able to dynamically adapt to the two main states found in process control: the steady state and the transient state. Key requirements to the...
Article
Full-text available
Automated control systems play an important part in many industrial domains and the medium used for communication between devices in these systems is in transition from wired to wireless for cost reasons. Control systems have strict requirements on delay, throughput, and reliability, that vary with time during operation. Addressing these requiremen...
Conference Paper
Full-text available
Model-based software engineering offers several attractive benefits for the implementation of protocols, including automated code generation for different platforms from design-level models. In earlier work, we have proposed a template-based approach using Coloured Petri Net formal models with pragmatic annotations for automated code generation of...
Article
Wireless Sensor Networks (WSNs) are applicable in numerous domains, including industrial automation where WSNs may be used for monitoring and control of industrial plants and equipment. However, the requirements in the industrial systems differ from the general WSN requirements. In recent years, standards have been defined by several industrial all...
Article
The sweep-line method allows explicit state model checkers to delete states from memory on-the-fly during state space exploration, thereby lowering the memory demands of the verification procedure. The sweep-line method is based on a least-progress-first search order that prohibits the immediate use of standard on-the-fly Büchi automata-based model...
Conference Paper
The inception of Wireless Sensor Actuator Networks from the existing Wireless Sensor Networks domain was motivated by the need to satisfy the requirements of automation applications. Automation applications cover a broad domain from industrial automation, home automation to automation in body area networks and have specific real-time requirements d...
Conference Paper
This article introduces a parallel state space exploration algorithm for shared memory multi-core architectures using state compression and state reconstruction to reduce memory consumption. The algorithm proceeds in rounds each consisting of three phases: concurrent expansion of open states, concurrent reduction of potentially new states, and conc...
Conference Paper
Full-text available
Model-driven software engineering (MDSE) provides a foundation for automatically generating software based on models that focus on the problem domain while abstracting from the details of underlying implementation platforms. Coloured Petri nets (CPNs) have been widely used to formally model and verify protocol software, but limited work exists on u...
Article
We describe a dynamic partitioning scheme useable by explicit state space exploration techniques that divide the state space into partitions, such as many external memory and distributed model checking algorithms. The goal of the scheme is to reduce the number of transitions that link states belonging to different partitions, and thereby limit the...
Article
Communication protocols constitute central building blocks in most modern IT systems as they define components, rules, and languages that make data communication possible. The development of correct protocols is a challenging engineering discipline, making modelling and validation of protocol design an important application domain for Coloured Petr...
Article
TinyOS is a widely used platform for the development of networked embedded systems offering a programming model targeting resource constrained devices. We present a software engineering approach where Coloured Petri Net (CPNs) models are used as a starting point for developing protocol software for the TinyOS platform. The approach consists of five...
Conference Paper
Full-text available
Formal modelling of protocols is often aimed at one specific purpose such as verification or automatically generating an implementation. This leads to models that are useful for one purpose, but not for others. Being able to derive models for verification and implementation from a single model is beneficial both in terms of reduced total modelling...
Conference Paper
The sweep-line method is an explicit-state model checking technique that uses a notion of progress to delete states from internal memory during state space exploration and thereby reduce peak memory usage. The sweep-line algorithm relies on the use of a priority queue where the progress value assigned to a state determines the priority of the state...
Conference Paper
The sweep-line method allows explicit state model checkers to delete states from memory on-the-fly during state space exploration thereby lowering the memory demands of the verification procedure. The sweep-line method is based on a least progress-first search order that prohibits the immediate use of standard on-the-fly LTL model checking algorith...
Article
The sweep-line method exploits intrinsic progress in concurrent systems to alleviate the state explosion problem in explicit state model checking. The concept of progress makes it possible to delete states from the memory during state space exploration and thereby reduce peak memory usage. The contribution of this paper is twofold. First, we provid...
Conference Paper
Model checking is applied for verification of concurrent systems by users having different skills and background. This ranges from researchers with detailed knowledge of the inner workings of the tools to engineers that are mostly interested in applying the technology as a black-box. This paper proposes JoSEL, a graphical language for specification...
Book
These Transactions publish archival papers in the broad area of Petri nets and other models of concurrency, ranging from theoretical work to tool support and industrial applications. ToPNoC issues are published as LNCS volumes, and hence are widely distributed and indexed. This Journal has its own Editorial Board which selects papers based on a rig...
Conference Paper
A storage system with file replication is an important element in supporting reliable and fault tolerant file access in many grid computing systems. The Chelonia distributed storage system is being developed in the context of the NorduGrid project. It provides transparent access to replicated files stored on a heterogeneous collection of storage no...
Conference Paper
Automatic code generation based on Coloured Petri Net (CPN) models is challenging because CPNs allow for the construction of abstract models that intermix control flow and data processing, making translation into conventional programming constructs difficult. We introduce Process-Partitioned CPNs (PP-CPNs) which is a subclass of CPNs equipped with...
Conference Paper
We provide a chronological research perspective on the development and application of methods and supporting computer tools for state space exploration and model checking of Coloured Petri Nets. We discuss how the lessons learned from practical applications have influenced current and envisioned future research directions concentrating on the ongoi...
Article
State caching is a memory reduction technique used by model checkers to alleviate the state explosion problem. It has traditionally been coupled with a depth-first search to ensure termination. We propose and experimentally evaluate an extension of the state caching method for general state exploring algorithms that are independent of the search or...
Conference Paper
We describe a dynamic partitioning scheme usable by model checking techniques that divide the state space into partitions, such as most external memory and distributed model checking algorithms. The goal of the scheme is to reduce the number of transitions that link states belonging to different partitions, and thereby limit the amount of disk acce...
Chapter
This chapter describes a course on the modelling and validation of concurrent systems based on this textbook which we have been giving at the Department of Computer Science, at Aarhus University. The course uses CP-nets as a formal modelling language for concurrency and exposes students to the benefits and applications of modelling for designing an...
Chapter
System development and engineering is a comprehensive discipline involving a multitude of activities such as requirements engineering, design and specification, implementation, testing, and deployment. An increasing number of system development projects are concerned with concurrent systems. There are numerous examples of this, ranging from large-s...
Conference Paper
The ASCoVeCo State space Analysis Platform (ASAP) is a tool for performing explicit state space analysis of coloured Petri nets (CPNs) and other formalisms. ASAP supports a wide range of state space reduction techniques and is intended to be easy to extend and to use, making it a suitable tool for students, researchers, and industrial users that wo...
Conference Paper
Coloured Petri nets (CP-nets or CPNs) is a widely used formalism for describing concurrent systems. CPN Tools provides a mature environment for constructing, simulating, and performing analysis of CPN models. CPN Tools also has limitations if, for example, one wishes to extend the analysis capabilities or to integrate CPN models into external appli...
Article
This chapter introduces the concepts of non-hierarchical Coloured Petri Nets. This is done by means of a running example consisting of a set of simple communication protocols. Protocols are used because they are easy to explain and understand, and because they involve concurrency, non-determinism, communication, and synchronisation which are key ch...
Article
This chapter gives an overview and some concrete examples of state space reduction methods. The main limitation of using state spaces to verify behavioural properties of systems is the state explosion problem [106], i.e., that state spaces of systems may have an astronomical number of reachable states, which means that they are too large to be hand...
Article
This chapter presents the CPN ML programming language for defining colour sets and functions, declaring variables, and writing inscriptions in CPN models. The previous chapter has provided a few simple examples of CPN ML programming. This chapter provides a comprehensive introductory road map to the CPN ML programming language. Many other examples...
Article
This chapter formally defines the syntax and semantics of hierarchical CPN models. Readers who are not interested in the mathematical definitions and are content with the informal introduction given in the previous chapter may decide to skip this chapter. The definition of hierarchical CPN models relies on the definition of nonhierarchical CPN mode...
Article
As illustrated in Chap. 2, a user of CPN Tools observes the execution of a CPN model directly in its graphical representation. Even though the CPN modelling language supports abstraction and a concept of hierarchical modules there can still be an overwhelming amount of detail in a constructed CPN model. Furthermore, observing every single step in a...
Article
This chapter shows how simulation of CPN models can be used to investigate the performance of systems and thereby evaluate their efficiency. Performance is a central issue in the design and configuration of concurrent systems, and performance analysis is conducted to evaluate existing or planned systems, to compare alternative implementations, and...
Article
This chapter contains the formal definition of non-hierarchical CP-nets and their behaviour. A non-hierarchical CP-net is defined as a many-tuple. However, it should be understood that the only purpose of this is to give a mathematically sound and unambiguous definition of CP-nets and their semantics. Any concrete net, created by a modeller, will a...
Article
This chapter gives a formal definition of the syntax and semantics of the nonhierarchical and untimed parts of the CPN modelling language. The formal definition is a supplement to the informal introduction provided in Chap. 2. Readers who are not interested in the mathematical definition and are content with the informal introduction may decide to...
Article
This chapter formally defines state spaces and behavioural properties. Readers who are not interested in the mathematical definitions and are content with the informal introduction given in Chap. 7 may decide to skip this chapter. The definition of state spaces relies on the definitions for non-hierarchical CPN models presented in Chap. 4, and it i...
Article
This chapter shows how a CPN model can be organised as a set of modules, in a way similar to that in which programs are organised into modules. There are several reasons why modules are needed. Firstly, it is impractical to draw a CPN model of a large system as a single net, since it would become very large and inconvenient. Although the net can be...
Article
This chapter introduces the basic state space method of CP-nets and shows how it can be used to investigate the behavioural properties of the protocol described in Chap. 2. The basic idea of state spaces is to calculate all reachable states (markings) and state changes (occurring binding elements) of the CPN model and to represent these in a direct...
Article
This chapter shows how timing information can be added to CPN models. This makes it possible to evaluate how efficiently a system performs its operations and it also makes it possible to model and validate real-time systems [78], where the correctness of the system relies on the proper timing of the events.With a timed CPN model, performance measur...
Chapter
This chapter presents a selection of representative projects where CP-nets and their supporting computer tools have been used for system development in an industrial context. These projects have been selected to illustrate the fact that CP-nets can be used in many different phases of system development, ranging from requirements specification to de...
Article
The ComBack method is a memory reduction technique for explicit state space search algorithms. It enhances hash compaction with state reconstruction to resolve hash conflicts on-the-fly thereby ensuring full coverage of the state space. In this paper we provide two means to lower the run-time penalty induced by state reconstructions: a set of strat...
Article
The Generic Access Network (GAN) architecture is defined by the 3rd Generation Partnership Project (3GPP) and allows telephone services, such as SMS and voice-calls, to be accessed via Internet Protocol (IP) networks. The main usage of this is to allow mobile phones to use WiFi in addition to the usual GSM network. The GAN specification relies on t...
Book
Coloured Petri Nets (CPN) is a graphical language for modelling and validating concurrent and distributed systems, and other systems in which concurrency plays a major role. The development of such systems is particularly challenging because of inherent intricacies like possible nondeterminism and the immense number of possible execution sequences....
Article
Semiconductor technology miniaturization allows designers to pack more and more transistors onto a single chip. The resulting Sys-tem on Chip (SoC) designs are predominant for embedded systems such as mobile devices. Such complex chips are composed of several subsys-tems called Intellectual Property blocks (IPs) which can be developed by independen...
Article
This paper shows how a formal method in the form of Colou- red Petri Nets (CPNs) and the supporting CPN Tools have been used in the development of the Course of Action Scheduling Tool (COAST). The aim of COAST is to support human planners in the specification and scheduling of tasks in a Course of Action. CPNs have been used to develop a formal mod...
Conference Paper
A mobile ad-hoc network (MANET) is an infrastructureless network established by a set of mobile devices using wireless communication. The Dynamic MANET On-demand (DYMO) protocol is a routing protocol for multi-hop communication in MANETs currently under development by the Internet Engineering Task Force (IETF). This paper presents a Coloured Petri...
Conference Paper
The Generic Access Network (GAN) architecture is defined by the 3rd Generation Partnership Project (3GPP), and allows telephone services, such as SMS and voice-calls, to be accessed via generic IP networks. The main usage of this is to allow mobile phones to use WiFi in addition to the usual GSM network. The GAN specification relies on the Internet...
Article
This paper describes a course on modelling and validation of concurrent systems given by the authors at the Department of Computer Science, University of Aarhus. The course uses Coloured Petri Nets (CPNs) as the formal modelling language for concurrency, and exposes students to the benefits and applications of modelling for designing and reasoning...
Conference Paper
The Configuration/Management Application Programming Interface (CMAPI) is a vendor-specific API and middlewarelayer for configuration and management of components in embedded systems. CMAPI is used by TietoEnator Denmark in the implementation of a controller for the Generic Access Network (GAN) architecture. This paper presents a hierarchical Colou...
Article
It is an ongoing trend that more and more information technology is incorporated into modern farms in order to increase productivity and comply with various documentation provisions. However, the potential of this is often not fully utilised due to the heterogeneous nature of the underlying communication technologies. Often, applications are unable...
Article
Coloured Petri Nets (CPNs) is a language for the modelling and validation of systems in which concurrency, communication, and synchronisation play a major role. Coloured Petri Nets is a discrete-event modelling language combining Petri nets with the functional programming language Standard ML. Petri nets provide the foundation of the graphical nota...
Article
The sweep-line state space method allows states to be deleted from memory during state exploration, thus alleviating the state explosion problem. Properties of the system (such as the absence of deadlocks) can then be verified on-the-fly. This paper presents an extension to the sweep-line method that allows on-the-fly checking of safety properties...
Article
Formal models of business processes support performance and behavioural analysis of the processes for continuous improvement. Formal models are also useful in guiding the development of software tools to support the processes. This paper presents a formal model of the operational planning process used in an operational headquarters of the Australia...
Conference Paper
This paper presents the ComBack method for explicit state space exploration. The ComBack method extends the well-known hash compaction method such that full coverage of the state space is guaranteed. Each encountered state is mapped into a compressed state descriptor (hash value) as in hash compaction. The method additionally stores for each state...
Article
State space analysis is one of the main approaches to model-based verification of concurrent systems and is one of the most successfully applied analysis methods for Coloured Petri Nets (CP-nets or CPNs) [13, 16, 17]. The basic idea of state space exploration and analysis is to compute all reachable states and state changes of the concurrent system...
Article
This paper presents two stubborn set methods for alleviating the state explosion problem when reasoning about state properties. The first method makes it possible to determine whether a state of the system is reachable in which a given state predicate holds. The second method makes it possible to determine if from all reachable states it is possibl...
Conference Paper
Vehicular ad-hoc networks is an emerging research area focussing on communication infrastructures that support vehicles and road-signs in distributing road-state data such as information about hazardous road conditions ahead, approaching emergency vehicles, and traffic delays. Vehicular ad-hoc networks combine the areas of sensor networks (data acq...
Chapter
In this paper, we describe the computer tool Design/CPN supporting editing, simulation, and state space analysis of Coloured Petri Nets. So far, approximately 40 man-years have been invested in the development of Design/CPN. It is used world-wide by more than 200 companies and research institutions. For the presentation, we draw from the experience...
Conference Paper
Full-text available
Object-based systems present particular challenges for state space exploration. Objects can be dynamically created and discarded, and can be referenced via object identifiers. Consistent relabelling of object identifiers in a state leads to a state that is superficially different but behaviourally equivalent to the original. Similarly, object-based...
Conference Paper
The LIWAS traffic warning system aims at providing early warning to vehicles about road conditions, such as whether the road is slippery. The LIWAS system is currently being developed and consists of two main parts: sensors for determining the state of the road and a communication infrastructure supporting inter-vehicle communication. This paper pr...
Conference Paper
We present an industrial project conducted at Ericsson Danmark A/S, Telebit where formal methods in the form of Coloured Petri Nets (CP-nets or CPNs) have been used for the specification of an interoperability protocol for routing packets between fixed core networks and mobile ad-hoc networks. The interoperability protocol ensures that a packet flo...
Article
Full-text available
The sweep-line state space method allows states to be deleted from memory during state exploration, thus alleviating state explosion. Properties of the system (such as the absence of deadlocks) can then be verifled on-the-∞y. This paper presents an extension to the sweep- line method that allows on-the-∞y checking of language inclusion, which is us...
Article
span style="font-family: Times New Roman; font-size: x-small;"> The LIWAS Traffic Warning System aims at providing early warning to vehicles about slippery conditions on the road. The LIWAS system is currently under development and consists of two main parts: sensors for measuring and classifying the state of the road, and a communication infrastr...
Article
Coloured Petri Nets (CPNs) are a graphically oriented modelling language for concurrent systems based on Petri Nets and the functional programming language Standard ML. Petri Nets provide the primitives for modelling concurrency and synchronisation. Standard ML provides the primitives for modelling data manipulation and for creating compact and par...
Conference Paper
Full-text available
We present an approach and associated computer tool sup-port for conducting distributed state space exploration for Coloured Petri Nets (CPNs). The distributed state space exploration is based on the in-troduction of a coordinating process and a number of worker processes. The worker processes are responsible for the storage of states and the compu...
Article
State-space exploration is one of the main approaches to computer-aided verification and analysis of finite-state systems. It is used to reason about a wide range of properties during the design phase of a system, including system deadlocks. Unfortunately, state-space exploration needs to handle huge state spaces for most practical systems. Several...
Article
The sweep-line method deletes states on-the-y during state space exploration to reclaim memory and thereby reduce peak memory usage. This deletion of states prohibits the immediate generation of, e.g., an error-trace when the violation of a safety property is detected. We address this problem by combining the sweep-line method with storing a spanni...
Conference Paper
We present an industrial project at Ericsson Telebit A/S where Coloured Petri Nets (CP-nets or CPNs) have been used for the design and specification of an edge router discovery protocol for mobile ad-hoc networks. The Edge Router Discovery Protocol (ERDP) supports an edge router in a stationary core network in assigning network address prefixes to...
Conference Paper
The sweep-line method deletes states on-the-fly during state space exploration to reduce peak memory usage. This deletion of states prohibits the immediate generation of, e.g., an error-trace when the violation of a safety property is detected. We address this problem by combining the sweep-line method with storing a spanning tree of the explored s...
Conference Paper
Full-text available
The mission system of an aircraft is a complex real-time distributed system consisting of a mission control computer, different kinds of devices interconnected by a number of serial data buses. The complexity and real-time requirements of mission systems have motivated research into the application of formal techniques to investigate and predict th...
Article
The mission system of an aircraft is a complex real-time distributed system consisting of a mission control computer, different kinds of devices interconnected by a number of serial data buses. The complexity and real-time requirements of mission systems have motivated research into the application of formal techniques to investigate and predict th...
Conference Paper
Full-text available
Coloured Petri Nets (CP-nets or CPNs) and their supporting computer tools have been used in a wide range of application areas such as communication protocols, software designs, and embedded systems. The practical application of CP-nets has also covered many phases of system development ranging from requirements to design, validation, and implementa...
Conference Paper
State space exploration is a main approach to verification of finite-state systems. The sweep-line method exploits a certain kind of progress present in many systems to reduce peak memory usage during state space exploration. We present a new sweep-line algorithm for a compositional setting where systems are composed of subsystems. The compositiona...
Article
The basic idea of the sweep-line state space method is to exploit a formal notion of progress found in many concurrent and distributed systems.
Conference Paper
Full-text available
The Internet Open Trading Protocol (IOTP) is being developed by the Internet Engineering Task Force for electronic commerce (e-commerce) over the Internet. The core of IOTP is a set of trading transactions that reflects the most common trading activities in the real world. We apply the formal method of Coloured Petri Nets (CP-nets) to construct an...
Conference Paper
The Wireless Transaction Protocol (WTP) is part of the Wireless Application Protocol (WAP) architecture and provides a reliable request-response service. The state space method of Coloured Petri Nets has been used to analyse a revised version of WTP, to gain a high level of confidence in the correctness of the design. Full state space analysis allo...
Conference Paper
The recently developed sweep-line method exploits progress present in many concurrent systems to explore the full state space of the system while storing only small fragments of the state space in memory at a time. A disadvantage of the sweep-line method is that it relies on a monotone and global notion of progress. This prevents the method from be...
Article
The avionics mission system of an aircraft is a complex realtime system consisting of a mission control computer, sensors, displays, controls, and connecting data buses. The complexity and real-time requirements of avionics mission systems represent major challenges to the Australian Defence Force when upgrading and maintaining aircraft. This has m...
Article
This paper presents a project where Hierarchical Coloured Petri Nets have been used to formally specify and analyse an operational planning process in a deployable Headquarters of the Australian Defence Force. A CPN model has been constructed for capturing the planning process, qualitative metrics have been defined for analysis of the planning proc...
Article
The avionics mission system of an aircraft is a complex realtime system consisting of a mission control computer, sensors, displays, controls, and connecting data buses. The complexity and real-time requirements of avionics mission systems represent major challenges to the Australian Defence Force when upgrading and maintaining aircraft. This has m...

Network