Airborne sensor platforms are becoming increasingly significant for both civilian and military operations; yet, at present, their sensors are typically idle for much of their flight time, e.g., while the sensor-equipped platform is in transit to and from the locations of sensing tasks. The sensing needs of many other potential information consumers might thus be served by sharing such sensors, thereby allowing other information consumers to opportunistically task them during their otherwise unscheduled time, as well as enabling other improvements, such as decreasing the number of platforms needed to achieve a goal and increasing the resilience of sensor tasks through duplication. We have implemented a prototype system realizing these goals in Mission-Driven Tasking of Information Producers (MTIP), which leverages an agent-based representation of tasks and sensors to enable fast, effective, and adaptive opportunistic sharing of airborne sensors. Using a simulated large-scale disaster-response scenario populated with publicly available Geographic Information System (GIS) datasets, we demonstrate that correlations in task location are likely to lead to a high degree of potential for sensor-sharing. We then validate that our implementation of MTIP can successfully carry out such sharing, showing that it increases the number of sensor tasks served, reduces the number of platforms required to serve a given set of sensor tasks, and adapts well to radical changes in flight path.

Airborne sensors are often idle for much of their flight, e.g., while the platform carrying them is in transit to and from the locations of sensor tasks. The sensing needs of many other potential information consumers might thus be served by sharing such sensors, allowing other information consumers to opportunistically task them during their otherwise unscheduled time. Toward this end, we have developed Mission-Driven Tasking of Information Producers (MTIP), a prototype system for opportunistic sharing of airborne sensors. This paper describes its implementation as an agent-based task allocation system on top of the Marti Quality of Service (QoS)-managed publish-subscribe information management system, and presents simulations of a disaster response scenario demonstrating how MTIP can increase the number of sensor tasks served as well as reducing the number of UAVs required to serve a given set of sensor tasks.

We address the problem of privacy in publish-subscribe(pub-sub) systems that typically expose some form of published content and subscriber interest, at least to the infrastructure responsible for subscription matching and content delivery. In our recent work, we proposed P3S, a pub-sub middleware designed to protect the privacy of subscriber interest and confidentiality of published content. P3S combined Cipher text Policy Attribute Based Encryption(CP-ABE) with Predicate Based Encryption (PBE) in its novel system architecture to achieve the desired level of content (payload and metadata) confidentiality, and subscription privacy. In this work, we build upon P3S to achieve the strongest possible subscription privacy where clear text subscription is visible only to the subscriber. Furthermore, we add support for subscription policy enforcement, improve the expressiveness of predicates by allowing disjunctions of conjunction, and improve the efficiency of the underlying cryptography through enhanced cryptographic construction and optimized implementation of cryptographic primitives. To the best of our knowledge, this paper presents the first comprehensive and practical implementation of a real-time privacy preserving pub-sub system, demonstrated on a large-scale test bed featuring up to 90 subscribers with robust, scalable and efficient performance. Our code and test bed specifications are freely available for research and experimentation purposes.

Mobile devices performing mission-critical functions at the tactical edge, such as those employed by first responders, military personnel, and law enforcement, operate in environments that are vastly different from enterprise computing environments. In spite of the differences in resource availability, threat models, vulnerabilities, information formats, and communication protocols, there is a great advantage to (and great demand for) enabling information exchange between the tactical edge and enterprise environments. Creating a specialized mobile version of each desired service that incorporates an appropriate level of security protection and quality of service (QoS) for the tactical users is one possibility. Such an approach is not cost effective, however, as the market for a given tactical application is small compared to the commercial user base for mobile applications and services. Furthermore, the need for information or services from the enterprise by tactical users can be too ad hoc and time critical, e.g., during disaster response, to support developing a specialized version. Finally, service specialization for mobile web access covers only one of multiple information dissemination and access patterns that arise in tactical operations. This paper presents the design and a prototype implementation of a gateway solution that provides secure tactical-enterprise information exchange and handles the differences in resource availability, QoS requirements, communication formats, and protocols.

Although IP and its overlying protocols, such as TCP and UDP, are ubiquitous, they were originally designed for point-to-point connections between computers in reasonably fixed locations. They are less suited to mobile networks and broadcast communications. In this paper, we present an alternative to IP that is based on a publish-subscribe approach. The approach that we present combines an application publish-subscribe programming model with a content delivery network, which provides several advantages in certain communication environments, including quality of service based on application level needs; efficient support for reliable broadcast; support for disadvantaged, intermittent, and limited communications; and more efficient reliability and fault tolerance. The paper presents our approach, based on a streamlined Data Distribution Service and simplified Content Delivery Network, a motivating example in which the publish-subscribe based distribution and network provides advantages, and a contrast to TCP/IP in the example context.

Wireless networking is moving toward the adoption of IP protocols and away from the multitude of special-purpose tactical radios traditionally in the hands of emergency personnel, military personnel, and law enforcement. The adoption of standards, such as IP multicast, has facilitated this. IP multicast also enables recovering some of the advantages of the broadcast medium when using IP in tactical environments. However, the traditional Quality of Service (QoS) approaches for IP multicast fall short of satisfying the stringent QoS requirements in tactical environments, which typically have single-hop, line-of-sight connections. The reasons for this are (1) QoS in IP networks, frequently based on Differentiated Services, relies on routers to enforce the priorities which typically don't exist in tactical networks, and (2) QoS for tactical users needs to be enforced at the information level, not the packet level where the loss or delay of a single packet can invalidate an entire object of information. We present strategies for QoS management for IP multicast in tactical environments that provides information and user-level QoS and addresses the specific challenges of tactical radios (such as the lack of reliable capacity information). We present our solutions in the context of a tactical information broker that provides beyond line-of-sight information management in a theater of operations.

SUMMARY SOA middleware has emerged as a powerful and popular distributed computing paradigm because of its high‐level abstractions for composing systems and encapsulating platform‐level details and complexities. Control of some details encapsulated by SOA middleware is necessary, however, to provide managed QoS for SOA systems that require predictable performance and behavior. This paper presents a policy‐driven approach for managing QoS in SOA systems called QoS enabled dissemination (QED). QED includes services for: (1) specifying and enforcing the QoS preferences of individual clients; (2) mediating and aggregating QoS management on behalf of competing users; and (3) shaping information exchange to improve real‐time performance. We describe QED's QoS services and mechanisms in the context of managing QoS for a set of Publish‐Subscribe‐Query information management services. These services provide a representative case study in which CPU and network bottlenecks can occur, client QoS preferences can conflict, and system‐level QoS requirements are based on higher level, aggregate end‐to‐end goals. We also discuss the design of several key QoS services and describe how QED's policy‐driven approach bridges users to the underlying middleware and enables QoS control based on rich and meaningful context descriptions, including users, data types, client preferences, and information characteristics. In addition, we present experimental results that quantify the improved control, differentiation, and client‐level QoS enabled by QED. Copyright © 2011 John Wiley & Sons, Ltd.

Service-oriented architecture (SOA) middleware has emerged as a powerful and popular distributed computing paradigm due to its high-level abstractions for composing systems and hiding platform-level details. Control of some details hidden by SOA middleware is necessary, however, to provide managed quality of service (QoS) for SOA systems that need predictable performance and behavior. This paper presents a policy-driven approach for managing QoS in SOA systems. We discuss the design of several key QoS services and empirically evaluate their ability to provide QoS under CPU overload and bandwidth-constrained situations.

Abstract Computing systems are increasingly distributed, real‐time, and embedded (DRE) and must operate under highly unpredictable and changeable conditions. A challenging problem for DRE systems is adaptation of behavior and reconfiguration of resources to maintain the best application performance in the face of changes in system load and available resources. To provide predictable mission‐critical quality of service (QoS) end‐to‐end, QoS‐enabled middleware services and mechanisms have begun to emerge, but they lack support for applications with stringent QoS requirements in changing, dynamic environments. This paper presents two contributions to research on adaptive and reconfigurable DRE systems. First, we describe the structure and functionality of an advanced middleware platform for developing applications that apply various techniques to adapt themselves to changes in resource availability to meet real‐time QoS requirements. Second, we present results of a case study of a multimedia application for Unmanned Aerial Vehicle (UAV) video distribution we developed using this middleware platform in conjunction with QoS‐enabledoperating systems and networking protocols. We describe the design of the multimedia application using our middleware platform and report empirical results showing how adaptive behavior and end‐to‐end resource management techniques are used to reconfigure the system dynamically to meet timeliness requirements. Copyright © 2006 John Wiley & Sons, Ltd.

As computer systems become increasingly internetworked, there is a growing class of distributed realtime embedded (DRE) applications that have characteristics and present challenges beyond those of traditional embedded systems. They involve many heterogeneous nodes and links, shared and constrained resources, and are deployed in dynamic environments with changing participants. In this paper, we present a representative DRE application of medium scale that we are developing for the DARPA PCES program. This application consists of several unmanned aerial vehicles, command and control centers, and ground based combat vehicles to perform surveillance, detection, and tracking of time critical targets, an ever increasing threat in today's world. We describe the application, the scenario in which the application is being demonstrated, and issues and challenges associated with developing a DRE application of this complexity.

Distributed real-time and embedded (DRE) systems in which application requirements and environmental conditions may not be known a priori-or which may vary at run-time-can benefit from an adaptive approach to management of quality-of-service (QoS) to meet key constraints, such as end-to-end timeliness. Moreover, coordinated management of multiple QoS capabilities across multiple layers of applications and their supporting middleware can help to achieve necessary assurances of meeting these constraints. We offer two contributions to the study of adaptive DRE computing systems: (1) a case study of our integration of multiple middleware QoS management technologies to manage quality and timeliness of imagery adoptively within a representative DRE avionics system and (2) empirical results and analysis of the impact of that integration on key tradeoffs between timeliness and image quality in that system.

In this paper we present a model-based approach for designing quality of service adaptive applications. We have developed a prototype distributed QoS modeling environment (DQME) that captures important elements of dynamic QoS adaptation at the model level. This modeling environment is designed independent of and can be integrated with, specific application domains to capture their QoS features and adaptation strategies. It combines the domain-specific modeling capability of the generic modeling environment with the QoS adaptation mechanisms of the quality objects middleware framework. DQME captures both the QoS and the functional concerns of distributed real-time embedded systems, and provides clear separation of these two. Integrated code-synthesis tools facilitate code generation and model refinement. We present a signal analyzer case study to demonstrate the use of the DQME modeling tool in real world applications.

In this paper, we present an approach for QoS management that can be applied to a general class of real-time distributed computation systems. In the proposed approach, a switching hybrid system model is used to represent the system. In this setting, the QoS specifications are transformed into set-point specifications and a limited-horizon online supervisory controller is used to move the system to the optimal operation point.

In this paper we present an approach for QoS management that can be applied for a general class of real-time distributed computation systems. In this paper, the QoS adaptation problem is formulated based on a utility function that measures the relative performance of the system. A limited-horizon online supervisory controller is used for this purpose. The online controller explores a limited region of the state-space of the system at each time step and decides the best action accordingly. The feasibility and accuracy of the online algorithm can be assessed at design time.

The Quality Objects (QuO) middleware is a set of extensions to standard distributed object computing middleware that is used to control and adapt the quality of service in a number of distributed application environments, from wide-area to embedded distributed applications. This paper compares and contrasts the characteristics of key use cases and the variations in QuO implementations that have emerged to support them. We present these variations in the context of several actual applications being developed using the QuO middleware.

Recent work in opening up distributed object systems to make them suitable for applications needing quality of service control has had the side effect of increasing the complexity in setting up, configuring, and initializing such applications. Configuration of distributed applications is more complicated than that of non-distributed applications, simply because of the heterogeneous and distributed nature of the application's components. CORBA and other distributed object middleware simplifies the configuration of distributed object applications, but hides much of the information and control necessary to achieve quality of service (QoS). We describe the techniques and tools that we have developed within our Quality Objects (QuO) framework for simplifying the configuration of distributed applications with QoS attributes. We describe a QuO configuration language, as well as the specific configuration needs of particular QoS properties-real-time, security, and dependability-and the support we provide for them.

As networks and the use of communications within applications continue to grow and find more uses, so too does the demand for more control and manageability of various "system properties" through middleware. An important component supporting an integrated property architecture is the concept of an object gateway, which is a quality-of-service (QoS)-aware element transparently inserted at the transport layer between clients and objects to provide managed communication behavior for the particular property being supported. In this paper, we introduce the concept of a QoS-oriented gateway to integrate a variety of QoS enforcement and implementation mechanisms controlling the underlying distributed interactions. We discuss the functions performed by such a component in achieving the desired overall end-to-end QoS, and the design considerations underlying our current implementation. We conclude with experiences to date with two variations of the gateway: one controlling managed latency and throughput using bandwidth allocation, and one controlling dependability through the coordination of object replicas.

Distributed applications are difficult to build and maintain and are even more difficult when the applications are distributed over wide-area networks. Distributed Object Computing middleware has emerged to simplify the building of distributed applications by hiding implementation details behind functional interfaces. However, critical applications have non-functional requirements, such as real-time performance, dependability, or security, that are as important as the functional requirements, but are also hidden by the middleware. Because current distributed object middleware doesn't support these aspects of critical applications, application developers often find themselves bypassing the distributed object systems, effectively gaining little or no advantage from the middleware. We have developed Quality Objects (QuO), a framework for including Quality of Service (QoS) in distributed object applications. QuO supports the specification of QoS contracts between clients and service providers, runtime monitoring of contracts, and adaptation to changing system conditions. A crucial aspect of QuO is a suite of Quality Description Languages for describing states of QoS, system elements that need to be monitored to measure the current QoS, and notification and adaptation to trigger when the state of QoS in the system changes. This paper gives a brief overview of QuO and describes the syntax and semantics of CDL, the component of QDL for describing QoS contracts.

Dependence analysis is useful for software maintenance because it indicates the possible effects of a software modification on the rest of a program. This helps the software maintainer evaluate the appropriateness of a software modification, drive regression testing, and determine the vulnerability of critical sections of code. A definition of interprocedural dependence analysis is given, and its implementation in a prototype tool that supports software maintenance is described.>