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Synchronization architectures, methods, systems, and computer readable media are described. One exemplary embodiment includes a first software component which is configured to cause retrieval and storage of structured data for a first data class from a first store of the structured data on a device, such as a first data processing system, and is configured to synchronize structured data for the first data class in the first store with structured data of the first data class in a second store on a host, such as a second data processing system. The first software component is separate from an application software which provides a user interface to allow a user to access and edit the structured data. The first software component synchronizes the structured data through a second software component which interfaces with the host and the device and which controls an order of synchronizing and a plurality of data classes including the first data class.

Synchronization methods and systems

Introduction This article describes some mathematical methods for verifying properties of programs in higher-order, functional languages. We focus on methods for reasoning about equivalence of expressions. Such methods are often based upon a denotational semantics of the programming language in question, using the mathematical theory of domains (Scott 1982; Plotkin 1981a). Here I will describe some methods which are based upon operational semantics (Plotkin 1981b). These operationally-based techniques have several attractive features. For example, there is relatively little mathematical overhead involved in developing the basic theory—in contrast with that needed to develop the existence and properties of recursively defined domains, the sine qua non of denotational semantics. On the other hand, domain theory provides an extremely powerful tool for analysing recursive program constructs. I believe that any serious attempt to develop a useful theory for verification of program properties has to involve both operational and denotational techniques. Highlights The main purpose of this article is to advertise the usefulness, for proving equivalences between functional programs, of co-inductive techniques more familiar in the context of concurrency theory (de Roever 1978; Park 1981; Milner 1989). They were imported into the world of lambda calculus and functional programming by several people: see Dybjer and Sander (1989); Abramsky (1990); Howe (1989, Howe (1996); Egidi, Honsell, and della Rocca (1992); and Gordon 1994.

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Semantics and Logics of Computation: Operationally-Based Theories of Program Equivalence

The Computational Complexity of Some Problems of Linear Algebra

This dissertation explores a uniform, relational proof style for operational arguments about program equivalences. It improves and facilitates many previously given proofs, and it is used to establish new proof rules for reasoning about term contexts, recursion, and nondeterminism in higher-order programming languages. Part I develops an algebra of relations on terms and exploits these relations in operational arguments about contextual equivalence for a typed deterministic functional language. Novel proofs of the basic laws, sequentiality and continuity properties, induction rules, and the CIU Theorem are presented together with new relational proof rules akin to Sangiorgi’s “bisimulation up to context” for process calculi. Part II extends the results from the first part to nondeterministic functional programs. May and must operational semantics and contextual equivalences are defined and their properties are explored by means of relational techniques. For must contextual equivalence, the failure of ordinary syntactic ω-continuity in the presence of countable nondeterminism is addressed by a novel transfinite syntactic continuity principle. The relational techniques are also applied to the study of lower and upper applicative simulation relations, yielding new results about their properties in the presence of countable and fair nondeterminism, and about their relationship with the contextual equivalences.

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Relational Reasoning about Functions and Nondeterminism

Operational, denotational and logical descriptions: a case study

The digital music revolution has improved the availability of music and made it easier to enjoy. The shift from hard support, such as audio CDs, to software leaves some unsatisfied by the loss of additional media contents, such as images, lyrics, and CD cover. We propose to fill the gap by enriching e-music with multimedia contents. Our proposal focuses specifically on MP3 as a widely distributed open format. The challenge we meet in enriching MP3 lies in maintaining audio compatibility and avoiding file size explosion. To this end, we define a description language to express multimedia contents in a textual way, with higher representation efficiency than existing languages. We also address security issues that arise from the use of an open format. Effectiveness is shown with an MP3 player capable of rendering multimedia contents.

Bringing multimedia contents into MP3 files

Better spaced seeds using Quadratic Residues

Sequencing technologies produce larger and larger collections of biosequences that have to be stored in compressed indices supporting fast search operations. Many compressed indices are based on the Burrows–Wheeler Transform (BWT) and the longest common prefix (LCP) array. Because of the sheer size of the input it is important to build these data structures in external memory and time using in the best possible way the available RAM. We propose a space-efficient algorithm to compute the BWT and LCP array for a collection of sequences in the external or semi-external memory setting. Our algorithm splits the input collection into subcollections sufficiently small that it can compute their BWT in RAM using an optimal linear time algorithm. Next, it merges the partial BWTs in external or semi-external memory and in the process it also computes the LCP values. Our algorithm can be modified to output two additional arrays that, combined with the BWT and LCP array, provide simple, scan-based, external memory algorithms for three well known problems in bioinformatics: the computation of maximal repeats, the all pairs suffix–prefix overlaps, and the construction of succinct de Bruijn graphs. We prove that our algorithm performs $${\mathcal {O}}(n\, \mathsf {maxlcp})$$
 sequential I/Os, where n is the total length of the collection and $$\mathsf {maxlcp}$$
 is the maximum LCP value. The experimental results show that our algorithm is only slightly slower than the state of the art for short sequences but it is up to 40 times faster for longer sequences or when the available RAM is at least equal to the size of the input.

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External memory BWT and LCP computation for sequence collections with applications.

Recently, Holt and McMillan [Bioinformatics 2014, ACM-BCB 2014] have proposed a simple and elegant algorithm to merge the Burrows-Wheeler transforms of a collection of strings. In this paper we show that their algorithm can be improved so that, in addition to the BWTs, it also merges the Longest Common Prefix (LCP) arrays. Because of its small memory footprint this new algorithm can be used for the final merge of BWT and LCP arrays computed by a faster but memory intensive construction algorithm.

Lavinia Egidi

Papers

Operational, denotational and logical descriptions: a case study

Bringing multimedia contents into MP3 files

Better spaced seeds using Quadratic Residues

External memory BWT and LCP computation for sequence collections with applications.

Lightweight BWT and LCP Merging via the Gap Algorithm