2,698 research outputs found

    Content Differences in Syntactic and Semantic Representations

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    Syntactic analysis plays an important role in semantic parsing, but the nature of this role remains a topic of ongoing debate. The debate has been constrained by the scarcity of empirical comparative studies between syntactic and semantic schemes, which hinders the development of parsing methods informed by the details of target schemes and constructions. We target this gap, and take Universal Dependencies (UD) and UCCA as a test case. After abstracting away from differences of convention or formalism, we find that most content divergences can be ascribed to: (1) UCCA's distinction between a Scene and a non-Scene; (2) UCCA's distinction between primary relations, secondary ones and participants; (3) different treatment of multi-word expressions, and (4) different treatment of inter-clause linkage. We further discuss the long tail of cases where the two schemes take markedly different approaches. Finally, we show that the proposed comparison methodology can be used for fine-grained evaluation of UCCA parsing, highlighting both challenges and potential sources for improvement. The substantial differences between the schemes suggest that semantic parsers are likely to benefit downstream text understanding applications beyond their syntactic counterparts.Comment: NAACL-HLT 2019 camera read

    ACMiner: Extraction and Analysis of Authorization Checks in Android's Middleware

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    Billions of users rely on the security of the Android platform to protect phones, tablets, and many different types of consumer electronics. While Android's permission model is well studied, the enforcement of the protection policy has received relatively little attention. Much of this enforcement is spread across system services, taking the form of hard-coded checks within their implementations. In this paper, we propose Authorization Check Miner (ACMiner), a framework for evaluating the correctness of Android's access control enforcement through consistency analysis of authorization checks. ACMiner combines program and text analysis techniques to generate a rich set of authorization checks, mines the corresponding protection policy for each service entry point, and uses association rule mining at a service granularity to identify inconsistencies that may correspond to vulnerabilities. We used ACMiner to study the AOSP version of Android 7.1.1 to identify 28 vulnerabilities relating to missing authorization checks. In doing so, we demonstrate ACMiner's ability to help domain experts process thousands of authorization checks scattered across millions of lines of code

    PASBio: predicate-argument structures for event extraction in molecular biology

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    Background: The exploitation of information extraction (IE), a technology aiming to provide instances of structured representations from free-form text, has been rapidly growing within the molecular biology (MB) research community to keep track of the latest results reported in literature. IE systems have traditionally used shallow syntactic patterns for matching facts in sentences but such approaches appear inadequate to achieve high accuracy in MB event extraction due to complex sentence structure. A consensus in the IE community is emerging on the necessity for exploiting deeper knowledge structures such as through the relations between a verb and its arguments shown by predicate-argument structure (PAS). PAS is of interest as structures typically correspond to events of interest and their participating entities. For this to be realized within IE a key knowledge component is the definition of PAS frames. PAS frames for non-technical domains such as newswire are already being constructed in several projects such as PropBank, VerbNet, and FrameNet. Knowledge from PAS should enable more accurate applications in several areas where sentence understanding is required like machine translation and text summarization. In this article, we explore the need to adapt PAS for the MB domain and specify PAS frames to support IE, as well as outlining the major issues that require consideration in their construction. Results: We introduce PASBio by extending a model based on PropBank to the MB domain. The hypothesis we explore is that PAS holds the key for understanding relationships describing the roles of genes and gene products in mediating their biological functions. We chose predicates describing gene expression, molecular interactions and signal transduction events with the aim of covering a number of research areas in MB. Analysis was performed on sentences containing a set of verbal predicates from MEDLINE and full text journals. Results confirm the necessity to analyze PAS specifically for MB domain. Conclusions: At present PASBio contains the analyzed PAS of over 30 verbs, publicly available on the Internet for use in advanced applications. In the future we aim to expand the knowledge base to cover more verbs and the nominal form of each predicate

    Maintaining the correctness of transactional memory programs

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    Dissertação para obtenção do Grau de Doutor em Engenharia InformáticaThis dissertation addresses the challenge of maintaining the correctness of transactional memory programs, while improving its parallelism with small transactions and relaxed isolation levels. The efficiency of the transactional memory systems depends directly on the level of parallelism, which in turn depends on the conflict rate. A high conflict rate between memory transactions can be addressed by reducing the scope of transactions, but this approach may turn the application prone to the occurrence of atomicity violations. Another way to address this issue is to ignore some of the conflicts by using a relaxed isolation level, such as snapshot isolation, at the cost of introducing write-skews serialization anomalies that break the consistency guarantees provided by a stronger consistency property, such as opacity. In order to tackle the correctness issues raised by the atomicity violations and the write-skew anomalies, we propose two static analysis techniques: one based in a novel static analysis algorithm that works on a dependency graph of program variables and detects atomicity violations; and a second one based in a shape analysis technique supported by separation logic augmented with heap path expressions, a novel representation based on sequences of heap dereferences that certifies if a transactional memory program executing under snapshot isolation is free from writeskew anomalies. The evaluation of the runtime execution of a transactional memory algorithm using snapshot isolation requires a framework that allows an efficient implementation of a multi-version algorithm and, at the same time, enables its comparison with other existing transactional memory algorithms. In the Java programming language there was no framework satisfying both these requirements. Hence, we extended an existing software transactional memory framework that already supported efficient implementations of some transactional memory algorithms, to also support the efficient implementation of multi-version algorithms. The key insight for this extension is the support for storing the transactional metadata adjacent to memory locations. We illustrate the benefits of our approach by analyzing its impact with both single- and multi-version transactional memory algorithms using several transactional workloads.Fundação para a Ciência e Tecnologia - PhD research grant SFRH/BD/41765/2007, and in the research projects Synergy-VM (PTDC/EIA-EIA/113613/2009), and RepComp (PTDC/EIAEIA/ 108963/2008
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