Network-wide Configuration Synthesis

Computer networks are hard to manage. Given a set of high-level requirements (e.g., reachability, security), operators have to manually figure out the individual configuration of potentially hundreds of devices running complex distributed protocols so that they, collectively, compute a compatible forwarding state. Not surprisingly, operators often make mistakes which lead to downtimes. To address this problem, we present a novel synthesis approach that automatically computes correct network configurations that comply with the operator's requirements. We capture the behavior of existing routers along with the distributed protocols they run in stratified Datalog. Our key insight is to reduce the problem of finding correct input configurations to the task of synthesizing inputs for a stratified Datalog program. To solve this synthesis task, we introduce a new algorithm that synthesizes inputs for stratified Datalog programs. This algorithm is applicable beyond the domain of networks. We leverage our synthesis algorithm to construct the first network-wide configuration synthesis system, called SyNET, that support multiple interacting routing protocols (OSPF and BGP) and static routes. We show that our system is practical and can infer correct input configurations, in a reasonable amount time, for networks of realistic size (> 50 routers) that forward packets for multiple traffic classes.Comment: 24 Pages, short version published in CAV 201

SemLAV: Local-As-View Mediation for SPARQL Queries

International audienceThe Local-As-View(LAV) integration approach aims at querying heterogeneous data in dynamic environments. In LAV, data sources are described as views over a global schema which is used to pose queries. Query processing requires to generate and execute query rewritings, but for SPARQL queries, the LAV query rewritings may not be generated or executed in a reasonable time. In this paper, we present SemLAV, an alternative technique to process SPARQL queries over a LAV integration system without generating rewritings. SemLAV executes the query against a partial instance of the global schema which is built on-the-fly with data from the relevant views. The paper presents an experimental study for SemLAV, and compares its performance with traditional LAV-based query processing techniques. The results suggest that SemLAV scales up to SPARQL queries even over a large number of views, while it significantly outperforms traditional solutions

Context-aware access to heterogeneous resources through on-the-fly mashups

Current scenarios for app development are characterized by rich resources that often overwhelm the final users, especially in mobile app usage situations. It is therefore important to define design methods that enable dynamic filtering of the pertinent resources and appropriate tailoring of the retrieved content. This paper presents a design framework based on the specification of the possible contexts deemed relevant to a given application domain and on their mapping onto an integrated schema of the resources underlying the app. The context and the integrated schema enable the instantiation at runtime of templates of app pages in function of the context characterizing the user’s current situation of use

ProSA - Using the CHASE for Provenance Management

Collecting, storing, tracking, and archiving scientific data is the main task of research data management, being the basis for scientific evaluations. In addition to the evaluation (a complex query in the case of structured databases) and the result itself, the important part of the original database used has also to be archived. To ensure reproducible and replicable research, the evaluation queries can be processed again at a later point in time in order to reproduce the result. Being able to calculate the origin of an evaluation is the main problem in provenance management, particularly in why and how data provenance. We are developing a tool called ProSA which combines data provenance and schema/data evolution using the CHASE for the different database transformations needed. Besides describing the main ideas of ProSA, another focus of this paper is the concrete use of our CHASE tool ChaTEAU for invertible query evaluation

Integration operators for generating RDF/OWL-based user defined mediator views in a grid environment

Research and development activities relating to the grid have generally focused on applications where data is stored in files. However, many scientific and commercial applications are highly dependent on Information Servers (ISs) for storage and organization of their data. A data-information system that supports operations on multiple information servers in a grid environment is referred to as an interoperable grid system. Different perceptions by end-users of interoperable systems in a grid environment may lead to different reasons for integrating data. Even the same user might want to integrate the same distributed data in various ways to suit different needs, roles or tasks. Therefore multiple mediator views are needed to support this diversity. This paper describes our approach to supporting semantic interoperability in a heterogeneous multi-information server grid environment. It is based on using Integration Operators for generating multiple semantically rich RDF/OWL-based user defined mediator views above the grid participating ISs. These views support different perceptions of the distributed and heterogeneous data available. A set of grid services are developed for the implementation of the mediator views

View Selection for Graph Pattern Matching

View-based techniques have been investigated on relational data, XML and graphs and proven effective for querying big data. While the pivot of using materialized views for query answering is view selection. Though explored for several years, the view selection problem for graph pattern matching has not been investigated. To this end, we investigate the problem in this paper. We first formalize the problem and show its intractability feature. We next propose an appropriate cost model and develop an effective algorithm to identify a set of view definitions under resource constraints, e.g., space storage and query processing cost, from a query workload. We finally verify the performance of the algorithms, and show that our view selection algorithm can identify a set of views that not only have low cost, e.g., storage space (below specified budget) and query processing cost but also can answer queries efficiently

Metadata Management for Data Lakes

International audienceTo prevent data lakes from being invisible and inaccessible to users, an efficient metadata management system is necessary. In this paper, we propose a such system based on a generic and extensible classification of metadata. A metadata conceptual schema which considers different types (structured, semi-structured and unstructured) of raw or processed data is presented. This schema is implemented in two DBMSs (relational and graph) to validate our proposal