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Ghosts for Lists: from Axiomatic to Executable Specifications

Ghosts for Lists: from Axiomatic to Executable Specifications

As future work we also plan to experiment with alternative specifications in the spirit of the work of Gladisch and Tyszberowicz [6]. In the case of JML, they used a pure observer method that takes a list object and an index, and returns the object at that index in the list, to specify Java methods on a linked list data structure. While the methods they consider are simpler than the list API of Contiki, our ghost arrays can essentially be seen as observations of the linked lists. We could consider such an observer directly written as a logical function in e-acsl. C pointers are however not Java references and can lead to some complications.
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On Flat Programs with Lists

On Flat Programs with Lists

The source of undecidability lies exactly in the complexity of the input data struc- ture. We noticed that the least common multiple relation can only be encoded by pro- grams running on input structures with at least two (separate) cycles. This observation leads to a decidability result, by imposing that the input heap has at most one cycle. We obtain decidability by first representing the program with lists as a counter automaton. The idea of modeling general programs with singly-linked lists as counter automata, originates in [8, 3]. However, due to the restricted form of our programs, we define a different encoding than the one described in [8, 3], that uses deterministic actions on counters, and preserves the flatness of the control structure. In consequence, we reduce the safety and termination problems from programs with lists to flat counter automata. Finally, we show that, for the latter we can effectively compute the exact loop invari- ants, using the decidable theory of [11]. In this way, we reduce the original problems of checking safety and termination to verifying validity of formulae in a known decidable logic.
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Ghosts for Lists: A Critical Module of Contiki Verified in Frama-C

Ghosts for Lists: A Critical Module of Contiki Verified in Frama-C

3 School of Informatics Computing and Cyber Systems, Northern Arizona University, USA frederic.loulergue@nau.edu Abstract. Internet of Things (IoT) applications are becoming increasingly crit- ical and require rigorous formal verification. In this paper we target Contiki, a widely used open-source OS for IoT, and present a verification case study of one of its most critical modules: that of linked lists. Its API and list representation differ from the classical linked list implementations, and are particularly chal- lenging for deductive verification. The proposed verification technique relies on a parallel view of a list through a companion ghost array. This approach makes it possible to perform most proofs automatically using the Frama-C/WP tool, only a small number of auxiliary lemmas being proved interactively in the Coq proof assistant. We present an elegant segment-based reasoning over the companion ar- ray developed for the proof. Finally, we validate the proposed specification by proving a few functions manipulating lists.
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Programs with Lists are Counter Automata

Programs with Lists are Counter Automata

1 Introduction The design of automatic verification methods for programs manipulating dynamic linked data structures is a challenging problem. Indeed, the analysis of the behaviour of such programs requires reasoning about complex transformations of data structures involv- ing both creation and deletion of objects as well as modifications of the links between them (pointer manipulations). The heap of such programs may have in fact an arbitrary size and shape (a graph structure). There are several approaches for tackling this prob- lem addressing different subclasses of programs and using different kinds of formalisms for representing and reasoning about infinite sets of heap structures, e.g., [19, 17, 21, 8]. We consider in this paper the class of programs manipulating linked data structures with a single data-field selector. It corresponds to programs manipulating linked lists with the possibility of sharing and circularities. We propose a new approach for the au- tomatic verification of such programs which is mainly based on using counter automata as accurate abstract (infinite-state) models. These models can be used for checking both safety properties and termination of the considered programs using techniques such as (abstract) symbolic reachability analysis (for safety and invariance checking) and auto- matic generation of decreasing ranking functions (for termination checking).
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Invariant Synthesis for Programs Manipulating Lists with Unbounded Data

Invariant Synthesis for Programs Manipulating Lists with Unbounded Data

{ abou,cezarad,cenea,sighirea } @liafa.jussieu.fr 2 Uppsala University, Sweden, rahmed@it.uu.se Abstract. We address the issue of automatic invariant synthesis for sequential programs manipulating singly-linked lists carrying data over infinite data do- mains. We define for that a framework based on abstract interpretation which combines a specific finite-range abstraction on the shape of the heap with an ab- stract domain on sequences of data, considered as a parameter of the approach. We instantiate our framework by introducing different abstractions on data se- quences allowing to reason about various aspects such as their sizes, the sums or the multisets of their elements, or relations on their data at different (linearly ordered or successive) positions. To express the latter relations we define a new domain whose elements correspond to an expressive class of first order univer- sally quantified formulas. We have implemented our techniques in an efficient prototype tool and we have shown that our approach is powerful enough to gen- erate non-trivial invariants for a significant class of programs.
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Quantitative Separation Logic and Programs with Lists

Quantitative Separation Logic and Programs with Lists

undecidable satisfiability problem. It is to be noticed that undecidability of QSL is not a direct consequence of the undecidability of Separation Logic [19], since the proof in [19] uses multiple selector heaps, while in this case we consider only heaps composed of singly-linked lists. Our result is non-trivial since it is well-known also that, even sim- ple logics, e.g. FOL, MSOL are decidable when interpreted over singly-linked lists, and become quickly undecidable when interpreted over grid-like, and more general graph structures.

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Keyphrase Extraction: Enhancing Lists

Keyphrase Extraction: Enhancing Lists

This research relies on Extractor (Turney, 1999) for the keyphrase extraction process. The resulting lists are usually presented in no apparent order; they are in fact sorted according to the system’s confidence. As a refinement, we suggest to present them in progression according to their informa- tiveness. Based on information theory (Shannon, 1948), the information content of a concept c is the negative log likelihood, − log p(c), where p(c) is the probability of encountering an instance of con- cept c. As the probability increases, informative- ness decreases. Therefore a general concept is more frequent than a specific one. We use the Wa- terloo MultiText System with a corpus of about one terabyte of unlabeled text (Clarke et al. 1995; Clarke and Cormak, 2000; Terra and Clarke, 2003) to approximate the information content of a key- phrase. We estimate informativeness by counting in the corpus the number of documents in which a keyphrase occurs. This is adequate as it gives the same ordering as the negative log likelihood.
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Do Inflation-Linked Bonds Still Diversify ?

Do Inflation-Linked Bonds Still Diversify ?

Quek (1998), Lamm (1998), Rudolph-Shabinsky and Trainer (1999)) showed that the correlation between the two markets should depend on whether nominal interest rate movements are more reflective of changes in real interest rates or changes in inflation expectations. Thus, when inflation expectations are moving the market more, IL bonds and nominal bonds tend to be less correlated, and when real rates vary, a higher correlation may be expected. The greater stability of inflation expectations could explain why real rates, while fluctuating in parallel with nominal rates, are much more highly correlated with inflation expectations. In addition, aspects of liquidity that are linked to the novelty of IL bonds may explain why their correlation was abnormally low at the beginning of the data series, when the indexed market was subject to significant supply / demand factors.
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LDScript: a Linked Data Script Language

LDScript: a Linked Data Script Language

7 Conclusion and Future Work Dedicated programming language enabling Semantic Web programmers to de- fine functions on RDF terms, RDF graphs or SPARQL results can improve modularity, reuse and maintenance of the code produced for Linked Data. This is the case when defining SPARQL extension functions, complex SPARQL filter expressions, functional properties associated to RDF resources and procedu- ral attachments as functions assigned to classes. To address these needs we detailed in this article a lightweight extension of SPARQL filter expression lan- guage to enable the definition of extension functions and we defined a Linked Data Script language on top of the SPARQL filter expression language. Com- pared to state-of-the-art we directly extend the SPARQL language in order to enable the definition of extension functions in the SPARQL language itself and using its native syntax, building on a well-known and widely accepted compo- nent of the Web of data. The key point of our proposal is that a programming language can easily be integrated in SPARQL to define extension functions. LDScript reuses the language of SPARQL filter expressions and extends it with several classical programming statements, among which function, let, for, eval and apply. We first provided an overview of the LDScript language and then we detailed the formal definition of the grammar of its syntax and the Natural Semantics inference rules of its semantics. We also provide a full im- plementation in the Corese Semantic Web Factory and we have developed a set of functions to validate our approach, some example of which were presented in this article.
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Browsing Linked Data Catalogs with LODAtlas

Browsing Linked Data Catalogs with LODAtlas

datasets. Here, we are more interested in interfaces that enable users to identify sources servings datasets relevant to their purposes, that can then be browsed using one of the above tools. Early Semantic Web keyword-based search engines, such as Swoogle [ 18 ] and Falcons [ 14 ], were already enabling users to identify data sources and vocabular- ies, even if indirectly: based on keywords input by the user, they would return vocabularies or “documents” containing instance data matching the search cri- teria. Those would be displayed to users as more-or-less flat lists of links to external resources (ontologies, RDF documents), or their content would be ex- posed as raw triples. Sindice.com [ 33 ] played a somewhat different role: given a certain RDF resource URI as input, the API would provide the client applica- tion (e.g., a linked data browser) with links to additional data sources contain- ing statements involving that resource URI as subject or object. The following generation of search engines, including SWSE [ 24 ] and Watson [ 17 ], provided significant improvements such as, e.g., displaying the information contained in the retrieved statements in a much more human-friendly manner (SWSE); and providing useful metadata about the source (Watson). The general concept re- mained essentially the same, however.
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LDScript: a Linked Data Script Language

LDScript: a Linked Data Script Language

Abstract. In addition to the existing standards dedicated to representa- tion or querying, Semantic Web programmers could really benefit from a dedicated programming language enabling them to directly define func- tions on RDF terms, RDF graphs or SPARQL results. This is espe- cially the case, for instance, when defining SPARQL extension functions. The ability to capitalize complex SPARQL filter expressions into exten- sion functions or to define and reuse dedicated aggregates are real cases where a dedicated language can support modularity and maintenance of the code. Other families of use cases include the definition of functional properties associated to RDF resources or the definition of procedural attachments as functions assigned to RDFS or OWL classes with the selection of the function to be applied to a resource depending on the type of the resource. To address these needs we define LDScript, a Linked Data script language on top of the SPARQL filter expression language. We provide the formal grammar of the syntax and the Natural Seman- tics inference rules of the semantics of the language. We also provide a benchmark and perform an evaluation using real test bases from W3C with different implementations and approaches comparing, in particular, script interpretation and Java compilation.
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Towards a Linked Open Code

Towards a Linked Open Code

Negotiating functions Users may take advantage of the implemented content negotiation to get suitable function definitions for their use-cases. This is done by using HTTP headers, or non-HTTP methods like Query String Arguments (QSA). Users negotiate functions that suit their current environment to access and manipulate Linked Data. For instance, a user working with Corese may send a request to the function catalog, asking for the Java implementation of functions alongside their query for data. Negotiation can rely on the previous step, by proposing the best function to the users according to their specifications. The realization of this vision would be a framework through which the user would use SPARQL to query a catalog of functions (section 2.1) for the im- plementations of needed functionalities meeting architectural and user-defined requirements. The fetched code artifacts can then be composed to build a tai- lored software system. However, the automatic composition of software artifacts
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Linked data based exploratory search

Linked data based exploratory search

4.2 Linked data browsers One of the first generation of tools designed to explore linked data was semantic browsers. Before their existence it was necessary to read the serialized RDF files to discover and understand the data. The first semantic browsers were strongly inspired by the web pages browsing and allowed the users to navigate into the linked data space in a one-resource-at-a-time mode, often by following the currently displayed resource outgoing property. Numerous systems were conceived and employed diverse approaches for lowering the visualization and interactions com- plexity. The display of the graph as it is has only a minor interest for end-user applications and further semantic-based processing is needed to obtain a compre- hensible and appealing navigation [ 89 ]. In this state-of-the-art survey we review the semantic web browsers according to a broad classification. Our first category is the text-based browsers. Our second category is the visualization-based browsers that use and potentially combine visual presentation(s) such as graphs, images, maps and timelines. Our third category is composed of faceted browsers. Faceted browsing is a successful interaction model that is particularly efficient for seman- tic data exploration. This interaction mode enables sorting and filtering the results thanks to their semantics. The fourth category named other browsing paradigms re- views innovative and singular browsing approaches enabled by linked data.
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Summarized Explanations from Linked Justifications

Summarized Explanations from Linked Justifications

Research Report n ° 8279 — April 2013 — 23 pages Abstract: A user of a Semantic Web application may not trust its results because he may not understand how the application produces its results using distributed data and inferential ca- pabilities. Explanation-aware Semantic Web applications provide explanations of their reasoning - explaining why an application has performed a given step or which information it has used to derive a new piece of information. However, providing too much and irrelevant information in explanations may overwhelm the users, especially the non-expert users. In this paper, we discuss an approach to explain reasoning over Linked Data. We introduce a vocabulary to describe justi- fications and we discuss how publishing justifications as Linked Data enables explaining reasoning over Linked Data. Finally, we discuss how to summarize explanations with relevant information taking into account user specified explanation filtering criterion.
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Bargaining with Linked Disagreement Points

Bargaining with Linked Disagreement Points

1. INTRODUCTION Many bargaining situations involve multiple issues at once. For instance, inter- national trade and environmental negotiations have often been put on the bargain- ing table in a linked fashion. From Kyoto in 1997 to Cartagena in 2003, interna- tional environmental agreements were negotiated with the lurking spectre of trade (dis)agreements like the WTO.

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Weaving a Web of Linked Resources

Weaving a Web of Linked Resources

2.5. Human-machine partnership This expanding Web of data, together with the schemas, ontologies and vocabularies used to structure and link it, form a formal Semantic Web with which we have to design new interaction means to support the next generation of Web applications. The Seman- tic Web has a role to play in addressing challenges at the intersection of knowledge-based interactions and Web-augmented interactions [11]: there is not only a need for Human Computer Interaction (HCI) to pro- vide methods to design human-data interaction applied to linked data on the Web, but also inversely a need for the Semantic Web community to investigate how linked data and the intelligent inferences they support can improve human-machine interactions. On the Web, large-scale interactions also create many challenges, and in particular the ongoing need to reconcile the formal semantics of computer science (logics, ontolo- gies, typing systems, etc.) on which the Web architec- ture is built, with the soft semantics of people (posts, tags, status, and so on) through which a lot of the Web content is created. And as the Web becomes a ubiq- uitous infrastructure reflecting all the objects of our world, we witness ever-increasing frictions between formal semantics and social semantics. A promising research avenue to span the gap between formal and social semantics is the use of Human Computation and Crowdsourcing techniques to involve large, distributed groups of users in the various stages of the knowl- edge engineering life-cycle, from ontology modeling and verification to annotation, data curation and entity linking [12].
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A linked data framework for Android

A linked data framework for Android

1 Introduction Smartphones are becoming our main personal information repositories. Unfortunately, this information is stored in independent silos managed by applications, thus it is diffi- cult to share data across them. One could synchronize application data, such as the con- tacts or the agenda using a central repository. However, these are not generic solutions and there is no mean to give access to data straight from the phone. The W3C Device API 1 covers this need across devices, but it offers specific APIs for specific applica- tions, and not a uniform and flexible access to linked data. Nowadays, mobile operating systems, such as Android, deliver solutions to access application content, but they are restricted to some application database schemas that must be known beforehand.
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SpiraList: A Compact Visualization Technique for One-Handed Interaction with Large Lists on Mobile Devices

SpiraList: A Compact Visualization Technique for One-Handed Interaction with Large Lists on Mobile Devices

Figure 1. (a) The WM 5.0 standard address book display. (b) A SpiraList displaying 100 contacts on a VGA PDA. Instead of adapting standard GUI techniques to mobile device, our approach consists in designing new techniques that take into account the strong constraints of mobile de- vices. The work presented in this paper introduces SpiraList (Figure 1b) a new interaction and visualization technique for displaying large lists (100 items or more) in an efficient way on small tactile screens. Inspired from previous works on visualization of serial periodic data [4,5], its spiral lay- out makes the most of concentric spiral revolutions to dis- play a large number of items in a limited amount of space. We have also designed appropriate interaction techniques that can be performed with fingers.
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A sex-linked Ace gene, not linked to insensitive acetylcholinesterase-mediated insecticide resistance in Culex pipiens

A sex-linked Ace gene, not linked to insensitive acetylcholinesterase-mediated insecticide resistance in Culex pipiens

were used: MSE (M) which is homozygous for an insecticide insensitive AChE1 (Bourguet et al ., 1996c; Raymond et al ., 1987); S-LAB (S) which is a standard insecticide susceptible strain[r]

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Online Relation Alignment for Linked Datasets

Online Relation Alignment for Linked Datasets

ETIS CNRS, University of Cergy-Pontoise, France maria.koutraki@kit.edu, nicoleta.preda@uvsq.fr, dan.vodislav@u-cergy.fr Abstract The large number of linked datasets in the Web, and their diversity in terms of schema representation has led to a fragmented dataset landscape. Query- ing and addressing information needs that span across disparate datasets requires the alignment of such schemas. Majority of schema and ontology alignment ap- proaches focus exclusively on class alignment. Yet, relation alignment has not been fully addressed, and existing approaches fall short on addressing the dy- namics of datasets and their size.
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