Overview of Recent Evolution in Database Technology

  • Filippo Cacace
  • Gianfranco Lamperti
Part of the Mathematics and Its Applications book series (MAIA, volume 371)

Abstract

The aim of this chapter is to give an overview of the recent evolution in database technology from the conceptual and practical perspective of the data modelling and data manipulation facilities provided by novel database systems.

Keywords

Logic Programming Query Language Integrity Constraint Relational Algebra Deductive Database 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Note

  1. 1.
    Observe that, in contrast with this interpretation, time is continuous in nature, that is isomorphic to real numbers, while discrete time is isomorphic to natural numbers, or a subset of natural numbers. However, both continuous and discrete interpretations assume that time is linearly ordered. Discrete interpretation of time is motivated by its simplicity and ease of implementation.Google Scholar
  2. 2.
    By contrast, as we shall see, the data model of Algres allows relations to be logically linked together by means of a special conceptual construct called link.Google Scholar
  3. 3.
    The whole set of dependents of a supervisor X includes the direct dependents of X, as well as all of the employees who are recursively dependent of the direct dependents of X.Google Scholar
  4. 4.
    The reader should not be confused by the use of the same variable names X and Y in the specification of rule constraintViolation and the relevant query. In the former, X and Y denote respectively the name and the age of the manager violating the constraint, while in the latter these variables are used to represent the name of the specific violated constraint and the list (that is the collection) of the variables participating in the incorrectness.Google Scholar
  5. 5.
    The transformation is based on the logical equivalence A ∧ (BC) = (AB) ∨ (AC). The latter is a disjunctive normal form as it consists of a disjunction of conjunctions. In contrast, a conjunctive normal form consists of a conjunction of disjunctions, such as (AB) ∧ (CD).Google Scholar
  6. 6.
    In object-oriented programming languages such as C++, objects of a given class are not automatically maintained in any container, so that set-oriented operations applied to the whole set of similar objects cannot be performed.Google Scholar
  7. 7.
    For practical reasons, in several object-oriented database systems, the set C1, C2, …, Cn of superclasses of a class C is actually an ordered set (a list).Google Scholar
  8. 8.
    Considering for example an attribute friend: Person, the restriction (or refinemant) of the domain of friend is a subclass of Person (e.g. Student).Google Scholar
  9. 9.
    It is also possible to use views to have as unit of authorization a subset of the tuples of a relation.Google Scholar
  10. 10.
    Besides objects, authorization hierarchies may also be defined for subjects and authorization types.Google Scholar
  11. 11.
    Recall that an exception is an error condition occurring in the execution of the operation.Google Scholar
  12. 12.
    The term triggered may be confusing as it might erroneously give the impression that the triggering of a rule means the execution of the action part of the rule. Triggering a rule means simply that, due to the occurrence of a relevant event, the condition part of the rule is evaluated and possibly (but of course not necessarily) the action part executed.Google Scholar
  13. 13.
    Active rules can be used to monitor traditional static integrity constraints as well as dynamic and realtime constraints, that is constraints on sequences of database states occurring over time. For example, a static constraint may specify that the salary of an employee cannot exceed the salary of the relevant manager, while a dynamic constraint might assert that the salary of an employee cannot be decreased.Google Scholar

Copyright information

© Springer Science+Business Media Dordrecht 1996

Authors and Affiliations

  • Filippo Cacace
    • 1
  • Gianfranco Lamperti
    • 2
  1. 1.Dipartimento di Informatica e SistemiUniversità di Napoli Federico IINaplesItaly
  2. 2.Dipartimento di Elettronica per l’AutomazioneUniversità degli Studi de BresciaBresciaItaly

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