Paolo Bottoni

Efficient parsing of visual languages based on critical pair analysis and contextual layered graph transformation

The paper proposes an extension of layered graph grammars (LGGs), which have been introduced for the definition of visual languages (VLs). Offering new constructs like negative application conditions (NACs) it allows one to produce more concise VL definitions. A new layering condition and critical pair analysis are the prerequisites for a new parsing algorithm which avoids the exponential behaviour of LGGs in many cases.

MADCOW: a multimedia digital annotation system

Digital annotation of multimedia documents adds information to a document (e.g. a web page) or parts of it (a multimedia object such as an image or a video stream contained in the document). Digital annotations can be kept private or shared among different users over the internet, allowing discussions and cooperative work. We study the possibility of annotating multimedia documents with objects which are in turn of multimedial nature. Annotations can refer to whole documents or single portions thereof, as usual, but also to multi-objects, i.e. groups of objects contained in a single document. We designed and developed a new digital annotation system organized in a client-server architecture, where the client is a plug-in for a standard web browser and the servers are repositories of annotations to which different clients can login. Annotations can be retrieved and filtered, and one can choose different annotation servers for a document. We present a platform-independent design for such a system, and illustrate a specific implementation for Microsoft Internet Explorer on the client side and on JSP/MySQL for the server side.

A Visualization of OCL Using Collaborations

We propose a visualization of OCL within the context of the UML meta model, so that OCL expressions are represented by extending collaboration diagrams. We exploit the OCL meta model introduced in [9] and further elaborated on in [1] and base the description of properties of objects on collaborations, while classifier and association roles are used to describe navigation paths. Operations computing properties are described by interactions consisting of messages between classifier roles. The introduction of new graphical core elements is kept to a minimum. New notation mainly concerns the predefined operations in OCL and provides more convenient visual forms for the notation by interactions here. The proposed visualization is described in detail and is illustrated with examples taken from an industrial project under development.

Specification and dialogue control of visual interaction through visual rewriting systems

Computers are increasingly being seen not only as computing tools but more so as communication tools, thus placing special emphasis on human-computer interaction (HCI). In this article, the focus is on visual HCI, where the messages exchanged between human and computer are images appearing on the computer screen, as usual in current popular user interfaces. We formalize interactive sessions of a human-computer dialogue as a structured set of legal visual sentences, i.e., as a visual language, and show how rewriting systems can be generalized to specify both the pictorial and the computational aspects of visual languages. To this end, Visual Conditional Attributed Rewriting (VCARW) systems are introduced, and use for specification of visual languages. These specifications are given as inputs to a procedure illustrated in the article as a system of algorithms, which automatically generates control mechanisms of the interaction, thus favoring the design of more reliable and usable systems.

Consistency checking and visualization of OCL constraints

Part of the success of the Unified Modeling Language (UML) as a specification language is due to its diagrammatic nature. Its meaning is expressed by its meta model, a combination of class diagrams and constraints written in the Object Constraint Language (OCL), a textual language of expressions. Recent efforts have tried to give a formal semantics to OCL in a classical way. In this paper, we propose a graph-based semantics for OCL and a systematic translation of OCL constraints into expressions over graph rules. Besides providing a semantical formalization of OCL, this translation can be employed to check the consistency of UML model instances wrt. the constraints, using a general purpose graph transformation machine like AGG or PROGRES. The translation of OCL constraints into graph rules suggests a way to express the constraints in a more intuitive visual form.

Membrane systems with promoters/inhibitors

Abstract. The computational model of membrane computing (formalized through membrane systems, also called P systems) is based on the way that biological membranes define compartments, each having its set of molecules and (enzymes enhancing) reactions, with compartments communicating through the transport of molecules through membranes. In this paper we augment the basic model of membrane systems with promoters and inhibitors, which formalize the reaction enhancing and reaction prohibiting roles of various substances (molecules) present in cells. We formalize such membrane systems with promoters/inhibitors and investigate their basic properties. In particular we establish universality results, i.e., we provide characterizations of recursively enumerable sets (of vectors of natural numbers) using these systems. It turns out that systems with promoters/inhibitors achieve universal computations without using the standard “auxiliary” features of membrane systems, for instance, without using catalysts.

Defining visual languages for interactive computing

A novel definition of visual languages allows a uniform approach to satisfying the needs of visual reasoning faced in visual human-computer interaction. The way the machine associates a computational meaning with an image, and conversely, the way it generates an image on the screen from a computation are formally described. A definition of a visual sentence and of a visual language as a set of visual sentences is discussed. A hierarchy of visual languages is derived in relation to the requirements for intelligible, manageable and trustable interaction between humans and computers.

Coordinated Distributed Diagram Transformation for Software Evolution

Abstract We present an approach to maintaining consistency between code and specification during refactoring, where a specification comprises several UML diagrams of different types. Code is represented as a flowgraph, and the flowgraph and UML diagrams constitute different views of a software system. A refactoring is modelled as a set of distributed graph transformations, organized into transformation units.

Specifying Integrated Refactoring with Distributed Graph Transformations

With refactoring, the internal structure of a software system changes to support subsequent reuse and maintenance, while preserving the system behavior. To maintain consistency between the code (represented as a flow graph) and the model (given by several UML diagrams of different kinds), we propose a framework based on distributed graphs. Each refactoring is specified as a set of distributed graph transformations, structured and organized into transformation units. This formalism could be used as the basis for important extensions to current refactoring tools.

Cooperative Visual Environments for the design of Effective Visual Systems

Abstract This paper describes the architecture of cooperative visual environments (CVE). This proposal stems from the findings of several experiments which suggested overcoming the limitations of first-generation user-interface management systems (UIMS) by allowing the users to determine their own computational environment. To avoid user disorientation, as well as the possibility of creating ambiguous or contradictory systems, a novel discipline for the specification and use of the tools is adopted. A systemic approach has been proposed to identify the variables needed to use, observe and adapt a CVE. The design and implementation of tools satisfying this discipline led to the definition of network objects, generalizing composite objects, and to the introduction of typed links allowing a new technique for message passing. The paper illustrates the above points by discussing the rationale behind the design of CVEs, deriving the requirements which CVEs have to satisfy and outlining the architecture with the fundamental mechanisms which allow their use and evolution. The nature of the proposal is also clarified through an example drawn from a real case.