A declarative SQL-like language and a middleware infrastructure are presented for collecting data from different nodes of a pervasive system. Data management is performed by hiding the complexity due to the large underlying heterogeneity of devices, which can span from passive RFID(s) to ad hoc sensor boards to portable computers. An important feature of the presented middleware is to make the integration of new device types in the system easy through the use of device self-description. Two case studies are described for PerLa usage, and a survey is made for comparing our approach with other projects in the area.

A language is presented for managing data in highly pervasive systems made of very different devices as to their technology and functional capabilities. Functional and nonfunctional requirements are dealt with in a transparent mode by a SQL like interface. In this paper the most relevant features of the language, the related data structures and some query examples are briefly introduced.

Nowadays user mobility requires that both content and services be appropriately personalized, in order for the (mobile) user to be always - and anywhere - equipped with the adequate share of data. Thus, the knowledge about the user, the adopted device and the environment, altogether called context, has to be taken into account in order to minimize the amount of information imported on mobile devices. The Context-ADDICT (Context-Aware Data Design, Integration, Customization and Tailoring) project aims at the definition of a complete framework which, starting from a methodology for the early design phases, supports mobile users through the dynamic hooking and integration of new, available information sources, so that an appropriate context-based portion of data, called data chunk, is delivered to their mobile devices. Data tailoring is needed because of two main reasons: the first is to keep the amount of information manageable, in order for the user not to be confused by too much, possibly noisy, information; the second is the frequent case when the mobile device is a small one, like a palm computer or a cellular phone, and thus only the most significant information must be kept on board. Context is, thus, key metainformation whose role becomes essential within the process of view design. Two main design-time activities are supported by our system in order to provide context-aware data filtering: 1) context design, based on a context model called context dimension tree and 2) definition of the relationship between each context and relevant portions of the application domain data.

Independent, heterogeneous, distributed, sometimes transient and mobile data sources produce an enormous amount of information that should be semantically integrated and filtered, or, as we say, tailored, based on the user’s interests and context. Since both the user and the data sources can be mobile, and the communication might be unreliable, caching the information on the user device may become really useful. Therefore new challenges have to be faced such as: data filtering in a context-aware fashion, integration of not-known-in-advance data sources, automatic extraction of the semantics. We propose a novel system named Context-ADDICT (Context-Aware Data Design, Integration, Customization and Tailoring) able to deal with the described scenario. The system we are designing aims at tailoring the available information to the needs of the current user in the current context, in order to offer a more manageable amount of information; such information is to be cached on the user’s device according to policies defined at design-time, to cope with data source transiency. This paper focuses on the information representation and tailoring problem and on the definition of the global architecture of the system.

The design of very small databases for smart cards and for portable embedded systems is deeply constrained by the peculiar features of the physical medium. We propose a joint approach to the logical and physical database design phases and evaluate several data structures with respect to the performance, power consumption, and endurance parameters of read/program operations on the Flash-EEPROM storage medium.

Modern information systems are the meeting point of the most advanced technologies both in the digital computers and in the telecommunications fields. Owing to their relevance on the everyday life, their availability became a major concern for system designers as well as for system managers. In this paper, we present an integration of the design and evaluation techniques as far as reliability and availability are concerned, in contrast with the duality existing between the computational functions and devices on one part and the telecommunications services and equipment on the other, which no longer snakes sense. To this scope, algorithmic components must be considered as part of the system, as well as the more traditional hardware and software components. A framework, including several research areas, is presented together with some results in the field of analytical models. The relations between the performance and the availability aspects in an Information System are also considered.

A method is proposed for quantitatively evaluating the availability of a distributed transaction system (DTS). The DTS dynamics can be modeled as a Markov process. The problem of formulating the set of linear homogeneous equations is considered, obtaining the related coefficient matrix, that is, the transition rate matrices of the DTS elements. Such operations can be performed according to the rules of Kronecker algebra. The transition rate matrices are used to calculate the probabilities of the different possible states of the DTS. The availability with respect to a transaction T is computed through its representation by means of a structure graph and a structure vector related to the probabilistic state of the DTS element relevant to the transaction T itself.

The problem of designing global applications in a Distributed Database is considered, and a multilevel model is developed in order to evaluate different access strategies. File manipulation operations are considered with respect to their possibility of distributed execution and their transmission requirements are defined. The need of an analysis of data is shown in order to quantitatively evaluate costs and delays of transmission operations.

Two methods for performing binary-BCD conversion of positive integers are discussed. The principle which underlies both methods in the repeated division by five and then by two, obtained the first by means of substructions performed from left to right, the second by shifting bits before next subtraction. It is shown that these methods work in a time which is linear with the length in bit of the number to be converted. A ROM solution is proposed and its complexity is compared with that of other methods.

The different requirements of the main software producers - Manufacturers, Software Houses and Users - are briefly examined. Then the Software House problems are considered in more detail as to the very different types of software it must produce and as to the necessity of fully utilising the internal know-how. The collection and generalization of already produced software semi-manufactures and the diffusion of their knowledge through a very concise form of documentation, called 'Software Configurator', is presented as a way for the know-how exploitation.