1,721,018 research outputs found
Ergodic Average in Constraint Programming (Extended Abstract)
No full text) Alessandra Di Pierro [email protected] Dipartimento di Informatica, Universita di Pisa, Italy Herbert Wiklicky [email protected] Department of Computing, Imperial College, London, UK July 22, 1999 1 Introduction We will discuss the problem of modelling probabilistic properties of constraint programs, which express the average of some quantities of interest. A random variable on the set of constraints is used for assigning to each constraint a real value representing the `cost' of that constraint. This way, we obtain a notion of quantitative observables Q which, although interesting in itself can be used in order to dene dierent types of average properties. One, E(Q) refers to the average over dierent runs of a probabilistic programs and corresponds to the expected value of the random variable. Another one, A(Q), considers the average value of the quantity along the same (innite) program run. In this work we concentrate on the second type of properties, which are also ..
Semantics of Probabilistic Programs: A Weak Limit Approach
No full textFor a simple probabilistic language we present a semantics
based on linear operators on infinite dimensional Hilbert spaces.We show the equivalence of this semantics with a standard operational one and we discuss its relationship with the well-known denotational semantics introduced by Kozen. For probabilistic programs, it is typical to use Banach spaces and their norm topology to model the properties to be analysed (observables). We discuss the advantages in considering instead
Hilbert spaces as denotational domains, and we present a weak limit construction of the semantics of probabilistic programs which is based on the inner product structure of this space, i.e. the duality between states and observables
Choreography and Orchestration Conformance for System Design
Full text linkIn a previous work we have presented a formal framework devoted to show the
relevance of choreography and orchestration in the design of service oriented applications.
Even if useful to start a formal investigation of the relationship between choreography
and orchestration, the proposed framework was
not suitable to specify real case studies. In fact,
it simply permitted to specify all possible computations abstracting
away from the conditions driving the choice of the actual behaviour.
In this paper we tackle this problem by introducing the notion of
state variables. The addition of state requires a substantial modification
of the entire framework because the same state variable, at the level of
choreography, can be actually stored in distributed orchestrators
that will need to synchronize in order to maintain consistent views.
In order to faithfully investigate this problem
we also need to modify the formal model at the orchestration level,
moving from synchronous to asynchronous communication as the latter
is the communication modality of the ordinary communication
infrastructures
Distributed Workflow upon Linkable Coordination Artifacts
No full textCoordination infrastructures can be used for the general-purpose support of WfMSs (workflow management systems). Suitably-expressive coordination artifacts can be specialised as workflow engines, encapsulating workflow rules expressed in terms of coordination laws.
In this paper, we focus on the issue of inter-organisational workflow (IOW), and show how the issue of multiple, interdependent, distributed workflows requires coordination artifacts to be linkable, so as to create a network of inter-connected coordination flows. After discussing a model of workflow engine based on ReSpecT tuple centres, we introduce a distributed workflow architecture based on TuCSoN, exploiting a logic-based workflow language. In particular, we focus on the definition of a scoping mechanism, and show how this enable workflows to be dynamically governed and distributed upon a coordination infrastructure based on artifact linkability
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
A Type Theory for Probabilistic { extdollar}{ extdollar}{ extbackslash}lambda { extdollar}{ extdollar}{ extendash}calculus
No full textWe present a theory of types where formulas may contain a choice constructor. This constructor allows for the selection of a particular type among a finite set of options, each corresponding to a given probabilistic term. We show that this theory induces a type assignment system for the probabilistic λ –calculus introduced in an earlier work by Chris Hankin, Herbert Wiklicky and the author, where probabilistic terms represent probability distributions on classical terms of the simply typed λ –calculus. We prove the soundness of the type assignment with respect to a probabilistic term reduction and a normalization property of the latter
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Program Synthesis and Linear Operator Semantics
Full text linkFor deterministic and probabilistic programs we investigate the problem of program synthesis and program optimisation (with respect to non-functional properties) in the general setting of global optimisation. This approach is based on the representation of the semantics of programs and program fragments in terms of linear operators, i.e. as matrices. We exploit in particular the fact that we can automatically generate the representation of the semantics of elementary blocks. These can then can be used in order to compositionally assemble the semantics of a whole program, i.e. the generator of the corresponding Discrete Time Markov Chain (DTMC). We also utilise a generalised version of Abstract Interpretation suitable for this linear algebraic or functional analytical framework in order to formulate semantical constraints (invariants) and optimisation objectives (for example performance requirements)
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