Teaching programming: A spiral approach to syntax and semantics

Coupling the recently proposed syntactic/semantic model of programmer behavior [1] with classic educational psychological theories yields new insights to teaching programming to novices. These new insights should make programming education more natural to students. alleviate “computer shock” (the analog of “math anxiety” [2]) and promote the development of widespread “computer literacy”.The spiral approach is the parallel acquisition of syntactic and semantic knowledge in a sequence which provokes student interest by using meaningful examples, builds on previous knowledge, is in harmony with the student's cognitive skills, provides reinforcement of recently acquired material and develops confidence through successful accomplishment of increasingly difficult tasks. The relationship of structured programming and flowcharts to the spiral approach is discussed.     

A feature-based syntax/semantics interface

Syntax/semantics interfaces using unification-based or feature-based formalisms are increasingly common in the existing computational linguistics literature. The primary reason for attempting to specify a syntax/semantics interface in feature structures is that it harmonizes so well with the way in which syntax is now normally described; this close harmony means that syntactic and semantic processing (and indeed other processing, see below) can be as tightly coupled as one wishes — indeed, there need not be any fundamental distinction between them at all. In this paper, we first point out several advantages of the unification-based view of the syntax/semantics interface over standard views. These include (i) a more flexible relation to nonsyntactic constraints on semantics, (ii) a characterization of semantic ambiguity, which in turn provides a framework in which to describe disambiguation, and (iii) the opportunity to underspecify meanings in a way difficult to reconcile with other views. The last point is illustrated with an application to the notorious scope ambiguity problem.     

Nesting in Euler Diagrams: syntax,semantics and construction

This paper considers the notion of nesting in Euler diagrams, and how nesting affects the interpretation and construction of such diagrams. After setting up the necessary definitions for concrete Euler diagrams (drawn in the plane) and abstract diagrams (having just formal structure), the notion of nestedness is defined at both concrete and abstract levels. The concept of a dual graph is used to give an alternative condition for a drawable abstract Euler diagram to be nested. The natural progression to the diagram semantics is explored and we present a nested form for diagram semantics. We describe how this work supports tool-building for diagrams, and how effective we might expect this support to be in terms of the proportion of nested diagrams.     

Ready to preorder: The case of weak process semantics

Recently, Aceto, Fokkink and Ingólfsdóttir proposed an algorithm to turn any sound and ground-complete axiomatisation of any preorder listed in the linear time-branching time spectrum at least as coarse as the ready simulation preorder, into a sound and ground-complete axiomatisation of the corresponding equivalence—its kernel. Moreover, if the former axiomatisation is ω-complete, so is the latter. Subsequently, de Frutos Escrig, Gregorio Rodríguez and Palomino generalised this result, so that the algorithm is applicable to any preorder at least as coarse as the ready simulation preorder, provided it is initials preserving. The current paper shows that the same algorithm applies equally well to weak semantics: the proviso of initials preserving can be replaced by other conditions, such as weak initials preserving and satisfying the second τ-law. This makes it applicable to all 87 preorders surveyed in “the linear time-branching time spectrum II” that are at least as coarse as the ready simulation preorder. We also extend the scope of the algorithm to infinite processes, by adding recursion constants. As an application of both extensions, we provide a ground-complete axiomatisation of the CSP failures equivalence for BCCS processes with divergence.     

Toward formalizing domain modeling semantics in language syntax

Information systems are situated in and are representations of some business or organizational domain. Hence, understanding the application domain is critical to the success of information systems development. To support domain understanding, the application domain is represented in conceptual models. The correctness of conceptual models can affect the development outcome and prevent costly rework during later development stages. This paper proposes a method to restrict the syntax of a modeling language to ensure that only possible configurations of a domain can be modeled, thus increasing the likelihood of creating correct domain models. The proposed method, based on domain ontologies, captures relationships among domain elements via constraints on the language metamodel, thus restricting the set of statements about the domain that can be generated with the language. In effect, this method creates domain specific modeling languages from more generic ones. The method is demonstrated using the Unified Modeling Language (UML). Specifically, it is applied to the subset of UML dealing with object behavior and its applicability is demonstrated on a specific modeling example.     

Rich meta object facility formal integration platform: syntax, semantics and implementation

Traditionally formal papers bridge interpretation gaps of informal OMG specifications. The papers are often not holistic but rather concentrate on certain aspects of the original specification. This increases often the gap between research and practice because it is difficult to understand and combine different semantic methodologies. This paper formalizes and extends the Meta Object Facility of the Object Management Group towards a platform to explore and combine formal methodologies. The extension focuses primarily on algorithms with an action language to define all kinds of normative and desired behavior. The methodology includes mechanisms to support arbitrary dependent language layers. Exemplary syntax and semantics of the methodology is introduced on base of the original specifications. This is complemented by an implementation supporting the graphical definition and simulation of instantiated models. The platform binding is supported by code generators allowing the easy connection of powerful analysis techniques. The platform binding can be done on all layers finding the optimal mixture between independent semantic variants currently in the discussion and established dependent semantic variants strengthening the bridge between research and practice.     

A method for describing the syntax and semantics of UML statecharts

In this article we present a method for describing the language of UML statecharts. Statecharts are syntactically defined as attributed graphs, with well-formedness rules specified by a set of first-order predicates over the abstract syntax of the graphs. The dynamic semantics of statecharts is defined by Abstract State Machines parameterized with syntactically-correct attributed graphs. The presented approach covers many important constructs of UML statecharts, including internal, completion, interlevel and compound transitions as well as history pseudostates. It also contains strategies to handle state entry/exit actions, state activities, synch states and choice pseudostates.     

Actor languages their syntax, semantics, translation, and equivalence

In this paper we present two actor languages and a semantics preserving translation between them. The source of the translation is a high-level language that provides object-based programming abstractions. The target is a simple functional language extended with basic primitives for actor computation. The semantics preserved is the interaction semantics of actor systems — sets of possible interactions of a system with its environment. The proof itself is of interest since it demonstrates a methodology based on the actor theory framework for reasoning about correctness of transformations and translations of actor programs and languages and more generally of concurrent object languages.     

Image retrieval by color semantics

The development of a system supporting querying of image databases by color content tackles a major design choice about properties of colors which are referenced within user queries. On the one hand, low-level properties directly reflect numerical features and concepts tied to the machine representation of color information. On the other hand, high-level properties address concepts such as the perceptual quality of colors and the sensations that they convey. Color-induced sensations include warmth, accordance or contrast, harmony, excitement, depression, anguish, etc. In other words, they refer to the semantics of color usage. In particular, paintings are an example where the message is contained more in the high-level color qualities and spatial arrangements than in the physical properties of colors. Starting from this observation, Johannes Itten introduced a formalism to analyze the use of color in art and the effects that this induces on the user's psyche. In this paper, we present a system which translates the Itten theory into a formal language that expresses the semantics associated with the combination of chromatic properties of color images. The system exploits a competitive learning technique to segment images into regions with homogeneous colors. Fuzzy sets are used to represent low-level region properties such as hue, saturation, luminance, warmth, size and position. A formal language and a set of model-checking rules are implemented to define semantic clauses and verify the degree of truth by which they hold over an image.     

Metric semantics from partial order semantics

In dealing with denotational semantics of programming languages partial orders resp. metric spaces have been used with great benefit in order to provide a meaning to recursive and repetitive constructs. This paper presents two methods to define a metric on a subset of a complete partial order such that is a complete metric spaces and the metric semantics on coincides with the partial order semantics on when the same semantic operators are used. The first method is to add a ‘length’ on a complete partial order which means a function of increasing power. The second is based on the ideas of [11] and uses pseudo rank orderings, i.e. monotone sequences of monotone functions . We show that SFP domains can be characterized as special kinds of rank orderded cpo's. We also discuss the connection between the Lawson topology and the topology induced by the metric. Received 11 July 1995 / 1 August 1996     

Building syntax graphs from syntax equations: A case study in modular programming

A system is described which inputs EBNF syntax equations as text, checks them and builds a corresponding syntax graph representation. An EBNF parser, with full error recovery, is included. The system is designed using the principles of modular decomposition and data abstraction, and is presented as a case study in the application of these principles to program design. The system is programmed in Pascal-plus, and has been used as a basis for the automatic generation of parsers.     

Image retrieval by texture similarity

Accuracy and efficiency are the two important issues in designing content-based image retrieval systems. In this paper, we present an efficient image retrieval system with high performance of accuracy based on two novel features, the composite sub-band gradient vector and the energy distribution pattern string. Both features are generated from the sub-images of a wavelet decomposition of the original image. A fuzzy matching mechanism based on energy distribution pattern strings serves as a filter to quickly remove undesired images in the database from further consideration. The images passing the filter will be compared with the query image based on composite sub-band gradient vectors which are extremely powerful for discriminating detailed textures. Through several extensive experiments by exercising our prototype system with a database of 2400 images, we demonstrated that both high accuracy and high efficiency can be achieved at the same time by our approach.     

Almost ASAP semantics: from timed models to timed implementations

In this paper, we introduce a parametric semantics for timed controllers called the Almost ASAP (as soon as possible) semantics. This semantics is a relaxation of the usual ASAP semantics (also called the maximal progress semantics) which is a mathematical idealization that cannot be implemented by any physical device no matter how fast it is. On the contrary, any correct Almost ASAP controller can be implemented by a program on a hardware if this hardware is fast enough. We study the properties of this semantics and show how it can be analyzed using the tool HyTech. A preliminary and short version of this paper appeared in the Proceedings of the 7th International Workshop on Hybrid Systems: Computation and Control (HSCC 2004), Lecture Notes in Computer Science, vol 2993, pp 296–310. This work was supported by the FRFC project ``Centre Fédéré en Vérification' funded by the Belgian National Science Fundation (FNRS) under grant nr 2.4530.02. Research fellow supported by the Belgian National Science Fundation (FNRS). Received November 2004 Revised April 2005 and May 2005 Accepted May 2005 by M. J. Butler     

Common knowledge: Relating anti-founded situation semantics to modal logic neighbourhood semantics

Two approaches for defining common knowledge coexist in the literature: the infinite iteration definition and the circular or fixed point one. In particular, an original modelization of the fixed point definition was proposed by Barwise (1989) in the context of a non-well-founded set theory and the infinite iteration approach has been technically analyzed within multi-modal epistemic logic using neighbourhood semantics by Lismont (1993). This paper exhibits a relation between these two ways of modelling common knowledge which seem at first quite different.A first version of this paper was written while the author was an assistant at the Universite Catholique de Louvain. It was part of a doctoral thesis presented in June 1992.     

Generating test programs from syntax

Summary The many faces of programming and systems development demand an immense amount of mechanical routine work. The present paper tries to explain some areas where automation of many tasks may be of great help. One special area, where progress seems to lag behind unduly, can be found in debugging, testing, and diagnosing systems. Here we attempted the generation of programs automatically from a definition of a problem and the characteristics of programs for its solution by a software system, which has been specially designed for this purpose. It has been indicated how the ideas underlying this project may be applied successfully to other areas.

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Zusammenfassung Bei der Programmierung und Systementwicklung wird zu einem erheblichen Umfang mechanische Routinearbeit erfordert. Der vorliegende Beitrag grenzt verschiedene Gebiete ab, wo mehrere Aufgabenlösungen automatisiert werden können. Ein Spezialgebiet, in welchem die Techniken auf niedrigem Stand zurückgeblieben scheinen, findet sich im Analysieren und Ausprüfen von Systemprogrammen. Hier haben wir versucht, Programme durch ein System automatisch zu erzeugen, ausgehend von einer Definition des Problems und den Charakteristiken seiner Lösung. Dieses System war zu diesem Zweck entwickelt worden. Ferner wird angedeutet, wie die Ideen, auf denen dieser Beitrag beruht, auf andere Gebiete erfolgreich angewendet werden können.

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With 18 Figures