This article presents Sharing User-Defined Aggregate Function (SUDAF), a declarative framework that allows users to write User-defined Aggregate Functions (UDAFs) as mathematical expressions and use them in Structured Query Language statements. SUDAF rewrites partial aggregates of UDAFs using built-in aggregate functions and supports efficient dynamic caching and reusing of partial aggregates. Our experiments show that rewriting UDAFs using built-in functions can significantly speed up queries with UDAFs, and the proposed sharing approach can yield up to two orders of magnitude improvement in query execution time. The article studies also an extension of SUDAF to support sharing partial results between arbitrary queries with UDAFs. We show a connection with the problem of query rewriting using views and introduce a new class of rewritings, called SUDAF rewritings, which enables to use views that have aggregate functions different from the ones used in the input query. We investigate the underlying rewriting-checking and rewriting-existing problem. Our main technical result is a reduction of these problems to, respectively, rewriting-checking and rewriting-existing of the so-called aggregate candidates , a class of rewritings that has been deeply investigated in the literature.

Computing aggregation over sliding windows, i.e., finite subsets of an unbounded stream, is a core operation in streaming analytics. We propose PBA (Parallel Boundary Aggregator), a novel parallel algorithm that groups continuous slices of streaming values into chunks and exploits two buffers, cumulative slice aggregations and left cumulative slice aggregations, to compute sliding window aggregations efficiently. PBA runs in O(1) time, performing at most 3 merging operations per slide while consuming O(n) space for windows with n partial aggregations. Our empirical experiments demonstrate that PBA can improve throughput up to 4X while reducing latency, compared to state-of-the-art algorithms.

When exploring and querying inconsistent data, inconsistency measures referring to constraint violations can help the user to quantify the quality of the underlying data and query results. We showcase INCA, a system that allows the user to execute data profiling and query answering tasks in an inconsistency-aware fashion. By using data instances annotated with novel inconsistency measures based on why-provenance and polynomial provenance, it becomes possible to visualize the share of the data which is consistent or inconsistent with respect to one or multiple denial constraints. Furthermore, data exploration by constraint or by subset of constraints allows to inspect the tuple violations according to multifaceted criteria. Finally, query profiling allows to enable inconsistency-aware query results accounting for most (in-)consistent top-k and threshold query results. To the best of our knowledge, INCA is the first system to allow such an inconsistency-driven analysis of both data and query results. Such an analysis is especially fruitful for enabling selective constraint-based data cleaning and inconsistency-aware ranking of query results in data science pipelines, thus leading to more explainable outputs of those processes.

We present SUDAF (Sharing User-Defined Aggregate Functions), a declarative framework that allows users to formulate UDAFs as mathematical expressions and use them in SQL statements. SUDAF rewrites partial aggregates of UDAFs using built-in aggregate functions and supports efficient dynamic caching and reusing of partial aggregates. Our evaluation shows that using SUDAF on top of Spark SQL can lead from one to two orders of magnitude improvement in query execution times compared to the original Spark SQL.

Automatic synthesis of web services business protocols (BPs) aims at solving algorithmically the problem of deriving a mediator that realizes a BP of a target service using a set of specifications of available services. This problem, and its variants, gave rise to a large number of fundamental research work over the last decade. However, existing works considered this problem under the restriction that the number of instances of an available service that can be involved in a composition is bounded by a constant [Formula: see text] which is fixed a priori. This paper investigates the unbounded variant of this problem using a formal framework in which web service BPs are described by means of finite state machines (FSM). We show that in this context, the protocol synthesis problem can be reduced to that of testing simulation preorder between an FSM and an (infinitely) iterated product of FSMs. Existing results regarding close decision problems in the context of the so-called shuffle languages are rather negative and cannot be directly exploited in our context. In this paper, we develop a novel technique to prove the decidability of testing simulation in our case of interest. We provide complexity bounds for the general protocol synthesis problem and identify two cases of particular interest, namely loop-free target services and hybrid states-free component services, for which protocol synthesis is shown to be respectively NP-COMPETE and EXPTIME-COMPLETE.

A home care plan defines the set of medical and/or social activities that are carried out day after day at a patient's home. Such a care plan is usually constructed through a complex process involving a comprehensive assessment of patient's needs as well as his/her social and physical environment. Specification of home care plans is challenging for several reasons: care plans are inherently non-structured processes which involve repetitive, but irregular, activities, whose specification requires complex temporal expressions. These features make home care plans difficult to model using traditional process modeling technologies. In this paper, we describe how home care plans, formalized as timed automata, can be generated from a set of high level and user-oriented abstractions. The resulting care plan encompasses all the possible allowed schedules of activities for a given patient. We discuss then how verification and monitoring of the resulting care plan can be handled using existing techniques and tools (e.g., UPPAAL model checker).

This paper introduces a scalable process event analysis approach, including parallel algorithms, to support efficient event correlation for big process data. It proposes a two-stages approach for finding potential event relationships, and their verification over big event datasets using MapReduce framework. We report on the experimental results, which show the scalability of the proposed methods, and also on the comparative analysis of the approach with traditional non-parallel approaches in terms of time and cost complexity.

Most of human activities are repetitive. Their explicit specification is necessary for many reasons especially to prepare their planning. This specification is generally made in a calendar form (developed form) but repetitions do not appear directly. Another solution consists in making this specification in an assertional form (condensed form) where repetitions are directly expressed in natural or quasi-natural language (i.e.: every day at 8 am except Sunday). Specifications under condensed form are easier to communicate and allows making more elaborated reasoning than the developed form. We propose in this paper a general model to express almost near regular repetitions in a condensed form. The irregularities appear for at least two reasons: the activity can be strengthened over some periods, exceptions exist some days. An illustration of our model is proposed to specify home care activities.

Web services are increasingly gaining acceptance as a framework for facilitating application-to-application interactions within and across enterprises. It is commonly accepted that a service description should include not only the interface, but also the business protocol supported by the service. The present work focuses on the formalization of an important category of protocols that includes time-related constraints (called timed protocols ), and the impact of time on compatibility and replaceability analysis. We formalized the following timing constraints: C-Invoke constraints define time windows within which a service operation can be invoked while M-Invoke constraints define expiration deadlines. We extended techniques for compatibility and replaceability analysis between timed protocols by using a semantic-preserving mapping between timed protocols and timed automata, leading to the identification of a novel class of timed automata, called protocol timed automata (PTA). PTA exhibit a particular kind of silent transition that strictly increase the expressiveness of the model, yet they are closed under complementation, making every type of compatibility or replaceability analysis decidable. Finally, we implemented our approach in the context of a larger project called ServiceMosaic, a model-driven framework for Web service life-cycle management.

In service-oriented computing, a conversation is a sequence of message exchanges between two or more services to achieve a certain goal, for example to order and pay for goods. A business protocol of a service is a specification of the possible conversations that a service can have with its partners. Motivated by the goal of facilitating the scalable development and maintenance of service oriented applications, especially in light of the many benefits of protocols, we have developed ServiceMosaic (servicemosaic.isima.fr), a platform for Web services life-cycle management. ServiceMosaic is an interactive and model-driven CASE tool for managing Web service interactions, which consists of two broad modules: protocol discovery and protocol management.

We present a software tool and a framework for security protocol change management. While we focus on trust negotiation protocols in this paper, many of the ideas are generally applicable to other types of protocols. Trust negotiation is a flexible approach to access control that is well suited to dynamic environments typical of service-oriented applications. However, managing the evolution of trust negotiation protocols is a difficult problem that has not been sufficiently addressed, especially in situations where there are ongoing negotiations. By using our framework, the consequences of changing the protocol that applies to ongoing trust negotiations can be automatically determined. We have also implemented a database-backed GUI tool to manage the change process as an extension of an existing system, and we have performed experiments to test the efficiency of our management software. Our experimental results show that the techniques proposed can scale to applications with tens of thousands of simultaneous users even on commodity PCs.

Digital images and video clips are becoming popular due to the increase in the availability of consumer devices that capture them. Digital content is also growing over the Internet. Applications that benefit from video are education and training, marketing support, medical, etc. The increase of this digital content creates a need for user-friendly tools to browse through large volumes of digital material. However, there are two basic impediments to wider use of digital video. The first is cataloging, which includes video digitization, compression and annotation, and the second is the lack of fast and effective search and browse techniques for this massive video content. The authors are interested in this second problem. One method that they believe is promising is the augmentation of a metadatabase with information on video content so that users can be guided to appropriate data sets. An automated technique is presented that combines manual annotations and knowledge produced by an automatic content characterization technique (i.e. clustering algorithms) to build higher level abstraction of video content.

This paper discusses a framework in which catalog service communities are built, linked for interaction, and constantly monitored and adapted over time. A catalog service community (represented as a peer node in a peer-to-peer network) in our system can be viewed as domain specific data integration mediators representing the domain knowledge and the registry information. The query routing among communities is performed to identify a set of data sources that are relevant to answering a given query. The system monitors the interactions between the communities to discover patterns that may lead to restructuring of the network (e.g., irrelevant peers removed, new relationships created, etc.).

More and more suppliers are offering access to their product or information portals (also called e-catalogs) via the Web. The key issue is how to efficiently integrate and query large, intricate, heterogeneous information sources such as e-catalogs. Traditional data integration approach, where the development of an integrated schema requires the understanding of both structure and semantics of all schemas of sources to be integrated, is hardly applicable because of the dynamic nature and size of the Web. We present WS-CatalogNet: a Web services based data sharing middleware infrastructure whose aims is to enhance the potential of e-catalogs by focusing on scalability and flexible aspects of their sharing and access.

Web services are emerging as a promising technology for the automation of inter-organizational interactions. As technology matures and the foundations of Web services become more solid, users will start to demand tools that facilitate the service development lifecycle. It is only when such tools become available that novel technologies become applied and enter the mainstream, since the complexity, cost and time necessary to deploy and manage solutions is dramatically reduced. In this paper, we present a framework and a tool that support the model-driven development of Web services. The idea consists in identifying key Web services abstractions, in addition to those of basic Web services standards, that enable the description of service policies and properties that are useful in practice. In this paper, we focus on service protocols, and specifically on conversation and trust negotiation protocols. These protocols are modeled by means of graphical tools and high-level languages so that they are easy to specify, understand, and evolve. The tools also support the automatic generation of service implementation skeletons based on these abstractions, manage the entire service lifecycle, and provide run-time support to verify that the interaction among clients and services occur in compliance with the specified policies.

In this paper we consider how constraint-based technology can be used to query semistructured data. We present a formalism based on feature logics for querying semistructured data. The formalism is a hybrid one in the sense that it combines clauses with path constraints. The resulting language has a clear declarative and operational semantics. These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

The paper describes a method to cope with denormalized relational schemas in a database reverse engineering process. We propose two main steps to improve the understanding of data semantics. Firstly we extract inclusion dependencies by analyzing the equi join queries embedded in application programs and by querying the database extension. Secondly we show how to discover only functional dependencies which influence the way attributes should be restructured. The method is interactive since an expert user has to validate the presumptions on the elicited dependencies. Moreover, a restructuring phase leads to a relational schema in third normal form provided with key constraints and referential integrity constraints. Finally, we sketch how an entity relationship schema can be derived from such information.

This paper introduces a method of reverse engineering for operational relational databases. The conceptual schemas are derived using information extracted from data dictionaries, database extensions and application programs. Its main strength relies on the assumptions made on the a priori knowledge available about the database (only [Formula: see text] and/or [Formula: see text] constraints on attribute(s)) as well as the user competence. We argue that most of the knowledge needed to build a conceptual schema, if not described in the Data Description Language, is embedded in application programs under various forms. The method is therefore based on four main steps: firstly, application program analysis is performed and a set [Formula: see text] of equi-joins is obtained; secondly, a conceptual schema is derived from [Formula: see text], from the database extension and from the relational schema; thirdly, this conceptual schema is validated through an interactive dialogue with the expert user who is helped in this task by indications given by the method. Finally, a schema reorganization under user control is achieved to match the user requirements better. We introduce also how other kinds of queries can help the task of semantics discovery. Additionally, we precisely identify the phases when user interaction is needed. This method has been successfully validated on an operational database.