Regular Expression Subtyping for XML Query and Update Languages

XML database query languages such as XQuery employ regular expression types with structural subtyping. Subtyping systems typically have two presentations, which should be equivalent: a declarative version in which the subsumption rule may be used anywhere, and an algorithmic version in which the use of subsumption is limited in order to make typechecking syntax-directed and decidable. However, the XQuery standard type system circumvents this issue by using imprecise typing rules for iteration constructs and defining only algorithmic typechecking, and another extant proposal provides more precise types for iteration constructs but ignores subtyping. In this paper, we consider a core XQuery-like language with a subsumption rule and prove the completeness of algorithmic typechecking; this is straightforward for XQuery proper but requires some care in the presence of more precise iteration typing disciplines. We extend this result to an XML update language we have introduced in earlier work.Comment: ESOP 2008. Companion technical report with proof

Schemas for Unordered XML on a DIME

We investigate schema languages for unordered XML having no relative order among siblings. First, we propose unordered regular expressions (UREs), essentially regular expressions with unordered concatenation instead of standard concatenation, that define languages of unordered words to model the allowed content of a node (i.e., collections of the labels of children). However, unrestricted UREs are computationally too expensive as we show the intractability of two fundamental decision problems for UREs: membership of an unordered word to the language of a URE and containment of two UREs. Consequently, we propose a practical and tractable restriction of UREs, disjunctive interval multiplicity expressions (DIMEs). Next, we employ DIMEs to define languages of unordered trees and propose two schema languages: disjunctive interval multiplicity schema (DIMS), and its restriction, disjunction-free interval multiplicity schema (IMS). We study the complexity of the following static analysis problems: schema satisfiability, membership of a tree to the language of a schema, schema containment, as well as twig query satisfiability, implication, and containment in the presence of schema. Finally, we study the expressive power of the proposed schema languages and compare them with yardstick languages of unordered trees (FO, MSO, and Presburger constraints) and DTDs under commutative closure. Our results show that the proposed schema languages are capable of expressing many practical languages of unordered trees and enjoy desirable computational properties.Comment: Theory of Computing System

Width-Dependent Band Gap in Armchair Graphene Nanoribbons Reveals Fermi Level Pinning on Au(111)

We report the energy level alignment evolution of valence and conduction bands of armchair-oriented graphene nanoribbons (aGNR) as their band gap shrinks with increasing width. We use 4,4\u2033-dibromo-para-terphenyl as the molecular precursor on Au(111) to form extended poly-para-phenylene nanowires, which can subsequently be fused sideways to form atomically precise aGNRs of varying widths. We measure the frontier bands by means of scanning tunneling spectroscopy, corroborating that the nanoribbon's band gap is inversely proportional to their width. Interestingly, valence bands are found to show Fermi level pinning as the band gap decreases below a threshold value around 1.7 eV. Such behavior is of critical importance to understand the properties of potential contacts in GNR-based devices. Our measurements further reveal a particularly interesting system for studying Fermi level pinning by modifying an adsorbate's band gap while maintaining an almost unchanged interface chemistry defined by substrate and adsorbate

Types from Data: Making Structured Data First-class Citizens in F#

Most modern applications interact with external services and access data in structured formats such as XML, JSON and CSV. Static type systems do not understand such formats, often making data access more cumbersome. Should we give up and leave the messy world of external data to dynamic typing and runtime checks? Of course, not! We present F# Data, a library that integrates external structured data into F#. As most real-world data does not come with an explicit schema, we develop a shape inference algorithm that infers a shape from representative sample documents. We then integrate the inferred shape into the F# type system using type providers. We formalize the process and prove a relative type soundness theorem. Our library significantly reduces the amount of data access code and it provides additional safety guarantees when contrasted with the widely used weakly typed techniques

Prospettive musicali. Dialogo filosofico-pedagogico sulla natura della musica e il su insegnamento

L'intento del volume è quello di sviluppare considerazioni che funzionino da coordinate per orientarsi nel variegato recolo dell'interrogazione pedagogico-filosofia sul 'musicale'. In tale direzione cercano di inoltrarsi, con una evidenza di intenti, la riflessione pedagogica e quella filosofia, in cui vengono presentati spunti argomentativi e non sentenze intorno a ciò che la musica del nostro tempo è, o non è. Esse dipanano il filo conduttore della ricaduta della musica nella'mbito filosofico e pedagogico

Public History tra didattica e comunicazione

L’evoluzione della Public History nel Salento ha seguito un percorso inverso rispettoad altre realtà accademiche, nel senso che si è radicata prima nel territorio e poi è approdata all’interno dell’Università del Salento, dapprima con la fondazione del Laboratorio Didattico di Progettazione e Realizzazione di Percorsi Formativi di Public History (LPH) presso il Consiglio dei Corsi di studio di Area Pedagogica dell’Università del Salento e, poi, con il seminario di studi sulla Public History dal titolo “Public History tra didattica e comunicazione”, tenutosi il 7 e l’8 novembre 2017 presso l’Ateneo salentino. Il presente volume raccoglie, infatti, i contributi di quell’iniziale atto ufficiale dicondivisione e di riflessione sulla Public History, I contributi pubblicati sono stati divisi in due sezioni: le “cornici teoriche” e i “luoghi d’esperienza”. Nella prima parte si problematizzano questioni più teoriche e di carattere generale, mentre nella seconda si rappresentano approcci ed esperienze di carattere più specifico e con intenzionalità più operative