Giorgio Gianforme

Model-independent schema translation

We discuss a proposal for the implementation of the model management operator ModelGen, which translates schemas from one model to another, for example from object-oriented to SQL or from SQL to XML schema descriptions. The operator can be used to generate database wrappers (e.g., object-oriented or XML to relational), default user interfaces (e.g., relational to forms), or default database schemas from other representations. The approach translates schemas from a model to another, within a predefined, but large and extensible, set of models: given a source schema S expressed in a source model, and a target model TM, it generates a schema S′ expressed in TM that is “equivalent” to S. A wide family of models is handled by using a metamodel in which models can be succinctly and precisely described. The approach expresses the translation as Datalog rules and exposes the source and target of the translation in a generic relational dictionary. This makes the translation transparent, easy to customize and model-independent. The proposal includes automatic generation of translations as composition of basic steps.

Semantic Web search based on ontological conjunctive queries

Many experts predict that the next huge step forward in Web information technology will be achieved by adding semantics to Web data, and will possibly consist of (some form of) the Semantic Web. In this paper, we present a novel approach to Semantic Web search, called Serene, which allows for a semantic processing of Web search queries, and for evaluating complex Web search queries that involve reasoning over the Web. More specifically, we first add ontological structure and semantics to Web pages, which then allows for both attaching a meaning to Web search queries and Web pages, and for formulating and processing ontology-based complex Web search queries (i.e., conjunctive queries) that involve reasoning over the Web. Here, we assume the existence of an underlying ontology (in a lightweight ontology language) relative to which Web pages are annotated and Web search queries are formulated. Depending on whether we use a general or a specialized ontology, we thus obtain a general or a vertical Semantic Web search interface, respectively. That is, we are actually mapping the Web into an ontological knowledge base, which then allows for Semantic Web search relative to the underlying ontology. The latter is then realized by reduction to standard Web search on standard Web pages and logically completed ontological annotations. That is, standard Web search engines are used as the main inference motor for ontology-based Semantic Web search. We develop the formal model behind this approach and also provide an implementation in desktop search. Furthermore, we report on extensive experiments, including an implemented Semantic Web search on the Internet Movie Database.

Semantic web search based on ontological conjunctive queries

Many experts predict that the next huge step forward in Web information technology will be achieved by adding semantics to Web data, and will possibly consist of (some form of) the Semantic Web. In this paper, we present a novel approach to Semantic Web search, which is based on ontological conjunctive queries, and which combines standard Web search with ontological background knowledge, as it is, e.g., available in Semantic Web repositories. We show how standard Web search engines can be used as the main inference motor for processing ontology-based semantic search queries on the Web. We develop the formal model behind this approach and also provide an implementation in desktop search. Furthermore, we report on extensive experimental results.

MIDST: model independent schema and data translation

MIDST is a tool for the translation of schemas and databases from a model to another, in a framework that is flexible and extensible with respect to the family of models. The major novelties with respect to existing proposals consist in the generation of data-level translations and on the customizability of translations (at both schema and data level).

MISM: A Platform for Model-Independent Solutions to Model Management Problems

Model management is a metadata-based approach to database problems aimed at supporting the productivity of developers by providing schema manipulation operators. Here we propose MISM (Model Independent Schema Management), a platform for model management offering a set of operators to manipulate schemas, in a manner that is both model-independent (in the sense that operators are generic and apply to schemas of different data models) and model-aware (in the sense that it is possible to say whether a schema is allowed for a data model). This is the first proposal for model management in this direction. We consider the main operators in model management: merge, diff, and modelgen. These operators play a major role in solving various problems related to schema evolution (such as data integration, data exchange or forward engineering), and we show in detail a solution to a major representative of the class, the round-trip engineering problem.

A runtime approach to model-independent schema and data translation

A runtime approach to model-generic translation of schema and data is proposed. It is based on our previous work on MIDST, a platform conceived to perform translations in an off-line fashion. In the original approach, the source database is imported into a dictionary, where it is stored according to a universal model. Then, the translation is applied within the tool as a composition of elementary transformation steps, specified as Datalog programs. Finally, the result is exported into the operational system. Here we illustrate a new, lightweight approach where the database is not imported. The tool needs only to know the model and the schema of the source database and generates views on the operational system that transform the underlying data (stored in the source schema) according to the corresponding schema in the target model. Views are generated in an almost automatic way, on the basis of the Datalog rules for schema translation.

A runtime approach to model-generic translation of schema and data

To support heterogeneity is a major requirement in current approaches to integration and transformation of data. This paper proposes a new approach to the translation of schema and data from one data model to another, and we illustrate its implementation in the tool MIDST-RT. We leverage on our previous work on MIDST, a platform conceived to perform translations in an off-line fashion. In such an approach, the source database (both schema and data) is imported into a repository, where it is stored in a universal model. Then, the translation is applied within the tool as a composition of elementary transformation steps, specified as Datalog programs. Finally, the result (again both schema and data) is exported into the operational system. Here we illustrate a new, lightweight approach where the database is not imported. MIDST-RT needs only to know the schema of the source database and the model of the target one, and generates views on the operational system that expose the underlying data according to the corresponding schema in the target model. Views are generated in an almost automatic way, on the basis of the Datalog rules for schema translation. The proposed solution can be applied to different scenarios, which include data and application migration, data interchange, and object-to-relational mapping between applications and databases.

A Universal Metamodel and Its Dictionary

We discuss a universal metamodel aimed at the representation of schemas in a way that is at the same time model-independent (in the sense that it allows for a uniform representation of different data models) and model-aware (in the sense that it is possible to say to whether a schema is allowed for a data model). This metamodel can be the basis for the definition of a complete model-management system. Here we illustrate the details of the metamodel and the structure of a dictionary for its representation. Exemplifications of a concrete use of the dictionary are provided, by means of the representations of the main data models, such as relational, object-relational or XSD-based. Moreover, we demonstrate how set operators can be redefined with respect to our dictionary and easily applied on it. Finally, we show how such a dictionary can be exploited to automatically produce detailed descriptions of schema and data models, in a textual (i.e. XML) or visual (i.e. UML class diagram) way.

Data model descriptions and translation signatures in a multi-model framework

We refer to the problem of translating schemas from a data model to another, in a multi-model framework. Specifically, we consider an approach where translations are specified as Datalog-like programs. In this context we show how it is possible to reason on models and schemas involved as input and output for a translation. The various notions are formalized: (i) concise descriptions of models in terms of sets of constructs, with associated propositional formulas; (ii) a notion of signature for translation rules (with the property that signatures can be automatically computed out of rules); (iii) the application of signatures to models. The main result is that the target model of a translation can be completely characterized given the description of the source model and the signatures of the rules. This result is being exploited in the framework of a tool that implements model generic translations, as the basis for the automatic generation of translations out of a library of elementary ones.

From Schema and Model Translation to a Model Management System

Model management addresses problems dealing with forms of collaboration among heterogeneous databases. This collaboration may include exchange of data, schema integration, synchronization, translation and, in general, any issue characterized by a data evolving scenario. It provides a structured framework allowing standard solutions to data programmability problems in terms of the application of some recurring operators. The main mid-term target in this field is the definition of a model management system, a software platform providing the data architect with a complete set of tools addressing a wide spectrum of possible problems. In this paper we recall MIDST, a platform that works as an applicator of schema transformations. It was firstly conceived to perform model-independent schema and data translation. Then it has been extended to an applicator of general schema transformations including model management operators. Leveraging on MIDST rich representation of models, schemas and data based on a metalevel approach, we reason about potentialities and possible developments of this platform with the target of laying the basis for a real runtime model management system.