In this paper we argue that developing information extraction (IE) programs using Datalog with embedded procedural extraction predicates is a good way to proceed. First, compared to current ad-hoc composition using, e.g., Perl or C++, Datalog provides a cleaner and more powerful way to compose small extraction modules into larger programs. Thus, writing IE programs this way retains and enhances the important advantages of current approaches: programs are easy to understand, debug, and modify. Second, once we write IE programs in this framework, we can apply query optimization techniques to them. This gives programs that, when run over a variety of data sets, are more efficient than any monolithic program because they are optimized based on the statistics of the data on which they are invoked. We show how optimizing such programs raises challenges specific to text data that cannot be accommodated in the current relational optimization framework, then provide initial solutions. Extensive experiments over real-world data demonstrate that optimization is indeed vital for IE programs and that we can effectively optimize IE programs written in this proposed framework. 1.

Declarative Networking is a programming methodology that enables developers to concisely specify network protocols and services, which are directly compiled to a dataflow framework that executes the specifications. This paper provides an introduction to basic issues in declarative networking, including language design, optimization and dataflow execution. We present the intuition behind declarative programming of networks, including roots in Datalog, extensions for networked environments, and the semantics of long-running queries over network state. We focus on a sublanguage we call Network Datalog (NDlog), including execution strategies that provide crisp eventual consistency semantics with significant flexibility in execution. We also describe a more general language called Overlog, which makes some compromises between expressive richness and semantic guarantees. We provide an overview of declarative network protocols, with a focus on routing protocols and overlay networks. Finally, we highlight related work in declarative networking, and new declarative approaches to related problems.

Network accountability, forensic analysis, and failure diagnosis are becoming increasingly important for network management and security. Such capabilities often utilize network provenance – the ability to issue queries over network meta-data. For example, network provenance may be used to trace the path a message traverses on the network as well as to determine how message data were derived and which parties were involved in its derivation. This paper presents the design and implementation of ExSPAN, a generic and extensible framework that achieves efficient network provenance in a distributed environment. We utilize the database notion of data provenance to “explain ” the existence of any network state, providing a versatile mechanism for network provenance. To achieve such flexibility at Internet-scale, ExSPAN uses declarative networking in which network protocols can be modeled as continuous queries over distributed streams and specified concisely in a declarative query language. We extend existing data models for provenance developed in database literature to enable distribution at Internet-scale, and investigate numerous optimization techniques to maintain and query distributed network provenance efficiently. The ExSPAN prototype is developed using Rapid-Net, a declarative networking platform based on the emerging ns-3 toolkit. Experiments over a simulated network and an actual deployment in a testbed environment demonstrate that our system supports a wide range of distributed provenance computations efficiently, resulting in significant reductions in bandwidth costs compared to traditional approaches.

In this paper, we present a declarative language and system for describing and implementing secure networks. Our proposed language, SeNDlog, is an attempt at unifying Binder, a logic-based language for access control in distributed systems, and Network Datalog (NDlog), a database query language for declarative networks. The contributions of this paper are as follows. First, we highlight the similarities and differences between Binder and NDlog with regards to their notion of location, trust model, and evaluation strategies. Second, we motivate and propose the SeNDlog language that combines features from Binder and NDlog. Third, we demonstrate the use of SeNDlog for specifying secure networks and present directions for future work. 1

In this paper, we present our initial design and implementation of a declarative network verifier (DNV). DNV utilizes theorem proving, a well established verification technique where logic-based axioms that automatically capture network semantics are generated, and a userdriven proof process is used to establish network correctness properties. DNV takes as input declarative networking specifications written in the Network Datalog (NDlog) query language, and maps that automatically into logical axioms that can be directly used in existing theorem provers to validate protocol correctness. DNV is a significant improvement compared to existing use case of theorem proving which typically require several man-months to construct the system specifications. Moreover, NDlog, a high-level specification, whose semantics are precisely compiled into DNV without loss, can be directly executed as implementations, hence bridging specifications, verification, and implementation. To validate the use of DNV, we present case studies using DNV in conjunction with the PVS theorem prover to verify routing protocols, including eventual properties of protocols in dynamic settings.

In recent years, data management has begun to consider situations in which data access is closely tied to network routing and distributed acquisition: sensor networks, in which reachability and contiguous regions are of interest; declarative networking, in which shortest paths and reachability are key; distributed and peer-to-peer stream systems, in which we may monitor for associations among data at the distributed sources (e.g., transitive relationships). In each case, the fundamental operation is to maintain a view over dynamic network state; the view is frequently distributed, recursive and may contain aggregation, e.g., describing transitive connectivity, shortest paths, least costly paths, or region membership. Surprisingly, solutions to this problem are often domain-specific, expensive to compute, and incomplete. In this paper, we recast the problem as one of incremental recursive view maintenance in the presence of distributed streams of updates to tuples: new stream data becomes insert operations and tuple expirations become deletions. We develop a set of techniques that maintain information about tuple derivability — a compact form of data provenance. We complement this with techniques to reduce communication: aggregate selections to prune irrelevant aggregation tuples, provenance-aware operators that can determine when tuples are no longer derivable and remove them from their state, and shipping operators that greatly reduce the tuple and provenance information being propagated while still maintaining correct answers. We validate our work in a distributed setting with sensor and network router queries, showing significant gains in bandwidth consumption without sacrificing performance. 1

Declarative languages have recently been proposed for many new applications outside of traditional data management. Since these are relatively early research efforts, it is important that the architectures of these declarative systems be extensible, in order to accommodate unforeseen needs in these new domains. In this paper, we apply the lessons of declarative systems to the internals of a declarative engine. Specifically, we describe our design and implementation of Evita Raced, an extensible compiler for the OverLog language used in our declarative networking system, P2. Evita Raced is a metacompiler: an OverLog compiler written in OverLog. We describe the minimalist architecture of Evita Raced, including its extensibility interfaces and its reuse of P2’s data model and runtime engine. We demonstrate that a declarative language like OverLog is well-suited to expressing traditional and novel query optimizations as well as other query manipulations, in a compact and natural fashion. Finally, we present initial results of Evita Raced extended with various optimization programs, running on both Internet overlay networks and wireless sensor networks. 1.

DKAL is a new declarative authorization language for distributed systems. It is based on existential fixed-point logic and is considerably more expressive than existing authorization languages in the literature. Yet its query algorithm is within the same bounds of computational complexity as e.g. that of SecPAL. DKAL’s communication is targeted which is beneficial for security and for liability protection. DKAL enables flexible use of functions; in particular principals can quote (to other principals) whatever has been said to them. DKAL strengthens the trust delegation mechanism of SecPAL. A novel information order contributes to succinctness. DKAL introduces a semantic safety condition that guarantees the termination of the query algorithm. 1.

This position paper outlines a new network architecture, i.e., a style of construction that identifies the objects and how they relate. We do not specify particular protocol implementations or specific interfaces and policies. After all, it should be possible to change protocols in an architecture without changing the architecture. Rather we outline the repeating patterns and structures, and how the proposed model would cope with the challenges faced by today’s Internet (and that of the future). Our new architecture is based on the following principle: Application processes communicate via a distributed interprocess communication (IPC) facility. The application processes that make up this facility provide a protocol that implements an IPC mechanism, and a protocol for managing distributed IPC (routing, security and other management tasks). Existing implementation strategies, algorithms, and protocols can be cast and used within our proposed new structure. 1.

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