Middleware: State of the Art and Challenges Ahead

Middleware: State of the Art and Challenges Ahead • Changing environment • Enterprise application integration: formerly independent applications must interaction to access and share functions and data store in heterogeneous DB • Internet applications • The number of users may fluctuate and be unpredictable • A stateful user session ins harder to maintain • Interacting parties belong to independent autonomous organizations that do not necessarily trust each other; insecure medium; • Communication infrastructure does not provide QoS guarantees • Open environment, need common ontologies • New application interoperate seamlessly with legacy applications • QoS • Nomadic mobility • Ubiquitous computing Challenges Ahead

Middleware: State of the Art and Challenges Ahead • Programming models • Client-Server??? • Asynchronous interaction • Shared memory • Mobile code and mobile agents • Architecture • Distribution transparency ??? • Layering ??? • Monolithic architectures (no adaptation, customization) • Dynamic Configuration • Disconnected operation • Adaptive applications • Ad hoc organization • intermediaries Challenges Ahead

Middleware: State of the Art and Challenges Ahead • Middleware • Shield software developers from low-level details • Amortize software lifecycle, providing reusable framework • Provide a consistent set of higher-level network-oriented abstractions • Provide a wide array of reusable services • Layered structure of middleware • Host infrastructure middleware • Distribution middleware • Common middleware services • Domain-specific middleware services • Domain-specific middleware services Challenges Ahead

Host infrastructure middleware • Encapsulates and enhances native OS communication and concurrency mechanisms to create reusable network programming components. • Java Virtual Machine • .Net • ACE Challenges Ahead

Distribution Middleware • Enable clients to program distributed application much like stand-alone applications by invoking operation son target objects without hard-coding dependencies of their location, programming language, OS platform, … • CORBA • RMI • DCOM • SOAP Challenges Ahead

Common Middleware Services • Augment distribution middleware by defining higher-level domain-independent services that allow application developers to concentrate on programming business logic, without the need to write the “plumbing” code required to develop distributed applications by using lower-level middleware • CORBA common object services, event notification, transaction, etc., • J2EE • .Net Web Service Challenges Ahead

Domain-Specific Middleware Services • Service targeted at vertical markets, such as telecom, e-commerce, healthcare • The Siemens Medical Engineering Group: Syngo • The Boeing Bold Stroke architecture uses COTS hardware and middleware to produce a non-proprietary, standards-based component architecture for military avionic mission computing capabilities Challenges Ahead

Areas of Focus • Growing focus on integration rather than on programming • Next generation applications will increasingly be assembled by modeling, integrating, and scripting domain-specific and common service components, rather than by being programmed either entirely from scratch or requiring significant customization or augmentation to off-the-shelf component implementations. • Increased viability of open systems architectures and open-source availability • Standard interfaces • Increased leverage for disruptive technologies leading to increased global competition • Growing focus on real-time embedded environments integrating computational and real world physical assets Challenges Ahead

Research Challenges and Strategies • Cause of complexity • Discrete platforms must be scaled to provide seamless end-to-end solutions • Components are heterogeneous yet they need to be integrated seamlessly • Most failures are only partial in that they effect subsets of the distributed components • Operating environments and configurations are dynamically changing • large-scale systems must operate continuously, even during upgrades • End-to-end properties must be satisfied in time and resource constrained environments • Maintaining system-wide QoS concerns is expected Challenges Ahead

Quality Object (QuO) • The QuO architecture decouples DOC middleware and applications along the following two dimensions: • Functional path: • Flows of information between client and remote server applications. • The middleware ensures that this information is exchanged efficiently, etc. • Information is largely application-specific and determined by the functionality being provided. • QoS attribute path: • Responsible for determining how well the functional interactions behave end-to-end with respect to key distributed system QoS properties • The middleware is responsible for collecting, organizing, and disseminating QoS-related meta-information that is needed to monitor and manage how well the functional interaction occur, and enable the adaptive and reflective decision-making needed to support QoS attribute properties in the face of rapidly changing environmental conditions. Challenges Ahead

Systems of Systems • Desired properties: • Predictability, controllability, and adaptability of operating characteristics for applications with respect to such features as time, quantity of information, accuracy, confidence, and synchronization. Challenges Ahead

Specific R&D Challenges • Providing end-to-end QoS support, not just component-level QoS • Adaptive and reflective solutions that handle both variability and control • Adaptive middleware is software whose functional and QoS-related properties can be modified either statically, or dynamically • Reflective middleware permits automated examination of the capabilities it offers and permits automated adjustment to optimize those capabilities. • Reflective middleware supports more advanced adaptive behavior and more dynamic strategies keyed to current circumstances, ie.., necessary adaptations can be performed autonomously based on conditions within the system, in the system’s environment or in system QoS policies defined by end-user Challenges Ahead

Specific R&D Challenges • Combining model-integrated computing with DOC middleware • Toward more universal use of standard middleware • Leveraging and extending the installed base Challenges Ahead

Fundamental Research Concepts • Contracts and adaptive meta-programming • Graceful degradation • Multiple behaviors are both feasible and desirable • Feedback loops so that the application services can degrade gracefully as condition change • Prioritization and physical world constrained load invariant performance • Higher level design approaches, abstractions, and software development tools Challenges Ahead

Promising Research Strategies • Individual QoS requirements • Translation of requests for service among and between the various entities on the distributed end-to-end path • Managing the definition and selection of appropriate applicati0n functionality and system resource tradeoffs with a “fuzzy” environment and • Maintaining the appropriate behavior under composability • Runtime requirements • Addresses the need for run-time monitoring, feedback and transition mechanisms to change application and system behavior, e.e., through dynamic reconfiguration, orchestrating degraded behavior or even off-line recompilation. Challenges Ahead

Promising Research Strategies • Aggregate Requirements • Addresses the system view of collecting necessary information over the set of resources across the system and providing resource management mechanisms and policies that are aligned with the goals of the system as a whole. • Reservations • Admission control mechanisms • Enforcement mechanism with appropriate scale, granularity and performance • Coordinated strategies and policies to allocate distributed resources that optimize various properties • Integration Requirements • Address the need to develop interfaces with key building blocks used for system construction, including the OS, network management, etc.. Challenges Ahead

Promising Research Strategies • Adaptivity requirements • Changes beneath the applications to continue to meet the required service levels despite changes in resource availability; • Changes at the application level to either react to currently available levels of service or request new ones under changed circumstances • System Engineering Methodologies and Tools • View-oriented or aspect-oriented programming techniques to support the isolation and the composition • Design time tools and model-integrated computing technologies to assist system developers in understanding their designs • Interactive tuning tools to overcome the challenges associated with the need for individual pieces of the system to work together in a seamless manner • Composability tools to analyze resulting QoS from combining two or more individual components • Modeling tools for developing system performance model • Debugging tools Challenges Ahead

Middleware: State of the Art and Challenges Ahead