This document summarizes a scientific dissertation to obtain a Master's degree in Engineering and Computer Science. The dissertation models and queries federated information systems. It presents a model to represent heterogeneous data models in federated systems using semantic descriptions. It also describes a query processor that allows SQL queries over the global data model without knowing the underlying partial models. The dissertation demonstrates its approach on two example data sources and concludes that its model and query processing method allow querying distributed, heterogeneous, and autonomous information systems through a global schema.

1. Modeling and
Querying Federated
Information Systems
Scientific dissertation performed to obtain the
Master's degree in Engineering and Computer Science
Author: Hugo Miguel Ferreira da Cruz
Supervisor: Paulo Manuel Trigo da Silva

2. Agenda
1.Federated information systems
2.Creating a federated model for the system
3.Querying over the federated model
4.Demonstration
5.Conclusions
2 Modeling And Querying Federated Information Systems 22-01-2012

3. Federated Information Systems
 A global vision over several (partial) information
systems
 Main characteristics:
 Distribution
 Heterogeneity
 Autonomy
3 Modeling And Querying Federated Information Systems 22-01-2012

4. Federated Information Systems
 Main challenges:
 Representing the different data models;
 Automating the creation of the global data model;
 Query processing;
 Finding and processing semantic data;
 Transactional processing.
4 Modeling And Querying Federated Information Systems 22-01-2012

5. Federated Information Systems
 Existing solutions
 Representing the different data models
 Relational model
 Objects model
 Semantic models
 Query processing
 Tailor-made solutions
 SQL variations
 SQL over virtual tables
5 Modeling And Querying Federated Information Systems 22-01-2012

6. Hypotheses
1. The formalisms that support semantic descriptions have
the expressive power to build a homogeneous view of
heterogeneous models.
2. The adoption the the query standard SQL (Structured
Query Language) remains valid in a context where the
uniform view is described by a model built on the
principles of hypothesis 1.
6 Modeling And Querying Federated Information Systems 22-01-2012

7. Representing the data models
 Semantic description model (in OWL)
 Partial models' structure (relational.owl)  TBoxP
 Partial models' Instances  ABoxP
 Global model  TBoxG
 Mapping between the partial models and the global model 
ABoxG
7 Configuração e Interrogação com Sistemas Federados 22-01-2012

8. Representing the data models
 Mapping capabilities
 Direct mapping
 Horizontal partitions
 Vertical partitions
 Replicas
 Constants
 Calculated columns
8 Modeling And Querying Federated Information Systems 22-01-2012

9. Querying the federated model
SQL (over the Query Results in relational
global model) processor model
 RowSet execute (String queryString);
 Supports:
 select.
 from.
 where.
 order by.
 group by.
 having.
9 Modeling And Querying Federated Information Systems 22-01-2012

10. Querying the federated model
10 Modeling And Querying Federated Information Systems 22-01-2012

11. Demonstration
Global data model Two data sources
MySQL database
BASE_MENSAL_DEAL
BASE_MENSAL_DEAL
ID_DEAL
ID_DEAL DATA_ULTIMA_MODIF
DATA_ULTIMA_MODIF …
…
Excel 2007 file
Contractos: <id_deal, contratacao, …>
Mapping for the global data model:
 MySQL database: direct mapping
 Excel
 ID_DEAL  id_deal
 DATA_ULTIMA_MODIF  ifEmpty(contratacao, 2010-07-20)
11 Modeling And Querying Federated Information Systems 22-01-2012

12. Contributions
A model do represent
federated information
systems (FIS);
A query processor over
FIS;
12 Modeling And Querying Federated Information Systems 22-01-2012

13. Conclusions
 The formalisms that support semantic description were adequate to the
description of a homogeneous view of heterogeneous models.
 It was possible to use query standard SQL
(Structured Query Language) as the basis for a
query processor for federated information systems
described by the created model.
 It is possible to run queries on distributed, heterogeneous
and autonomous information systems only knowing the
global data model.
13 Modeling And Querying Federated Information Systems 22-01-2012

14. Modeling and Querying Federated
Information Systems
Author: Hugo Miguel Ferreira da Cruz
Supervisor: Paulo Manuel Trigo da Silva
14 Modeling And Querying Federated Information Systems 22-01-2012