Renzo Orsini

GALILEO: a strongly-typed, interactive conceptual language

Galileo, a programming language for database applications, is presented. Galileo is a strongly-typed, interactive programming language designed specifically to support semantic data model features (classification, aggregation, and specialization), as well as the abstraction mechanisms of modern programming languages (types, abstract types, and modularization). The main contributions of Galileo are (a) a flexible type system to model database structure and semantic integrity constraints; (b) the inclusion of type hierarchies to support the specialization abstraction mechanisms of semantic data models; (c) a modularization mechanism to structure data and operations into interrelated units (d) the integration of abstraction mechanisms into an expression-based language that allows interactive use of the database without resorting to a new stand-alone query language. Galileo will be used in the immediate future as a tool for database design and, in the long term, as a high-level interface for DBMSs.

Fibonacci: a programming language for object databases

Fibonacci is an object-oriented database programming language characterized by static and strong typing, and by new mechanisms for modeling data-bases in terms of objects with roles, classes, and associations. A brief introduction to the language is provided to present those features, which are particularly suited to modeling complex databases. Examples of the use of Fibonacci are given with reference to the prototype implementation of the language.

Spatio-temporal aggregations in trajectory data warehouses

In this paper we investigate some issues related to the design of a simple Data Warehouse (DW), storing several aggregate measures about trajectories of moving objects. First we discuss the loading phase of our DW which has to deal with overwhelming streams of trajectory observations, possibly produced at different rates, and arriving in an unpredictable and unbounded way. Then, we focus on the measure presence, the most complex measure stored in our DW. Such a measure returns the number of trajectories that lie in a spatial region during a given temporal interval. We devise a novel way to compute an approximate, but very accurate, presence aggregate function, which algebraically combines a bounded amount of measures stored in the base cells of the data cube.

Approximate Aggregations in Trajectory Data Warehouses

In this paper we discuss how data warehousing technology can be used to store aggregate information about trajectories and perform OLAP operations over them. To this end, we define a data cube with spatial and temporal dimensions, discretized according to a regular grid. We investigate in depth some issues related to the computation of a holistic aggregate function, i.e, the presence, which returns the number of distinct trajectories occurring in a given spatio-temporal area. In particular, we introduce a novel way to compute an approximate, but nevertheless very accurate, presence aggregate function, which uses only a bounded amount of measures stored in the base cells of our cuboid. We also concentrate on the loading phase of our data warehouse, which has to deal with an unbounded stream of trajectory observations. We suggest how the complexity of this phase can be reduced, and we analyse the errors that this procedure induces at the level of the sub-aggregates stored in the base cells. These errors and the accuracy of our approximate aggregate functions are carefully evaluated by means of tests performed on synthetic trajectory datasets.

An Overview of Sidereus: A Graphical Database Schema Editor for Galileo

Sidereus is a workstation based graphical tool to edit a Galileo database schema using a diagrammatic notation. Several tools to manipulate a graphic representation of a database schema exist as commercial products or research prototypes, but the novel aspects of this proposal lie in the fact that the graphical editor is used to model a database using a semantic data model, to deal with complex objects with the values of attributes definable using the rich type system of Galileo, a database language that supports the abstraction mechanisms of semantic data models. Moreover, schemes designed with Sidereus are translated automatically in Galileo code, executable on the same workstation.

A formal specification for casanova, a language for computer games

In this paper we present the specification and preliminary assessment of Casanova, a newly designed computer language which integrates knowledge about many areas of game development with the aim of simplifying the process of engineering a game. Casanova is designed as a fully-fledged language, as an extension language to F#, but also as a pervasive design pattern for game development.

Towards an environment for designing and evaluating multimedia art guides

We discuss the design and implementation environment of a family of multimedia guides for art exhibitions on Apple iPod touch devices. The project aims at developing a unique framework adaptable to different content types and presentation styles, while retaining a common interface model with consistent gestures and a fast development process based on standard environments and toolkits. Evaluation is based on automatic collection of information about the user behavior by logging user actions.

The type system of Galileo

Galileo is a conceptual language, i.e., a programming language for database applications which supports both the abstraction mechanisms of modern programming languages (data types, abstract data types, modules) and the abstraction mechanisms of semantic data models (SDM) (classification, aggregation, generalization). Unlike other conceptual languages, Galileo is a strongly typed language which exploits the benefits of data types for modeling the abstract knowledge of information systems. The type system of Galileo has been designed to deal with the intensional aspects of the SDM abstraction mechanisms, while the class and subclass mechanism is provided to deal with the extensional aspects. The following relevant features of the type system will be emphasized: type hierarchies and declarative overloading, which provide a kind of polymorphism in a strongly typed language whose range of applications goes beyond the scope of conceptual modeling.

Designing Casanova: A Language for Games

Games are complex pieces of software which give life to animated virtual worlds. Game developers carefully search the difficult balance between quality and efficiency in their games.

Design of an integrated query and manipulation notation for database languages

A common task in data intensive applications is to locate a group of items and then manipulate them, e.g. to give a bonus to all of the employees in a department. Conventional relational query languages like SQL provide facilities for such manipulation-queries, but are not smoothly integrated with a programming language and lack computational power. It has been argued that comprehensions, a construct found in some languages, are a good query notation for database programming languages. An extension to comprehensions is proposed that permits the data to be manipulated by side-effect in addition to being queried. These side-effecting queries are computationally powerful and smoothly integrated into a database programming language, unlike conventional relational query languages. Furthermore side-effecting comprehensions are concise and some may be automatically optimized.<<ETX>>