New Approach for the Modeling and the Implementation of the Object-Relational
Databases
Amel Grissa-Touzi, and Minyar Sassi
remain limited to some concepts always. Indeed, these tools
Abstract—Conception is the primordial part in the realization of leave always is the E/A diagram in the case of PowerAMC, a computer system. Several tools have been used to help inventors to Designer, either of the class diagram in the case of Rational describe their software. These tools knew a big success in the Rose for modeling the object-relational databases or object-relational databases domain since they permit to generate SQL script
oriented databases.
modeling the database from an Entity/Association model. However,
In 2000, SOUTOU introduced in [7] a model called with the evolution of the computer domain, the relational databases
proved their limits and object-relational model became used more navigational model that permits of modeling all new object-and more. Tools of present conception don't support all new concepts relational database concepts and more precisely the new introduced by this model and the syntax of the SQL3 language. We concepts introduced with the SQL3 language. SOUTOU has propose in this paper a tool of help to the conception and specify in [1] rules of passage of this model toward the UML implementation of object-relational databases called «NAVIG-class diagram and toward the language SQL3. He showed the
TOOLS\" that allows the user to generate script modeling its database
in SQL3 language. This tool bases itself on the Entity/Association possible choice number that can have an object-relational
database inventor to pass navigational model toward the and navigational model for modeling the object-relational databases.
implementation of the basis with SQL3 in addition. This
Keywords—Abstract Data Table, Navigational model, Object-model will be primordial in the conception of the object-relational databases, References. relational databases.
We present in this paper a tool of conception and modeling
I. INTRODUCTION of object-relational databases, based on the navigational
model, called NAVIG_TOOLS. This tool gives to the inventor T the end years 90, a new generation of databases
management systems called object relational was born. It the possibility to draw the E/A model, to help him to define intends to remedy the weak points of the present systems and his navigational model of his object-relational database and to to permit a power of modeling importing (semantically rich) deduct the corresponding script of it in language SQL3, while and offer all other functionalities of database management using rules of passage proposed by SOUTOU [7]. We have system. This system is based on the extended relational model tried to adopt the same interfacings of PowerAMC, so that to the main concepts of object-oriented model (extensibility of users who familiarize already find again quickly.
The remainder of paper is organized in six sections. Section the set of type, complex structures, object identity, inheritance
II presents object-relational databases technologies. Section and methods) [1]-[2]-[3].
Currently, all big constructors of databases management III presents conception of object-relational databases. Section systems are conscious of limits of the relational model and IV describes the navigational model. Section V is devoted to propose systems of this type. They even participated in the the description of our tool called NAVIG-TOOLS. The development of the norm of the new version of SQL, SQL3. balance of this work and its future perspectives are discussed As example of databases management systems, we can in Section VI. mention Informix, Postgres, oracle [1]-[2].
II. OBJECT-RELATIONAL TECHNOLOGIES Several computer solutions have been proposed trying of
enrich their tools to can modelize the object-oriented concept The object-relational technology was born in 1992, it is as the inheritance, classes etc. Among these tools, we illustrate therefore new enough on the market of database management the Win'Design[4], PowerAMC[4], Rational Rose[4]-[5], systems. Currently, all big publishers of database management Designer [4]and JDevelopper [4]-[6] etc. But these tools systems are conscious of limits of the relational model. They
saw therefore in the object-relational model a manner to
enrich this model. Informix was the first publisher of Manuscript received Mai 20, 2005. management systems to raise the challenge of the object-A Grissa-Touzi M. Sassi, with the Department of Electrical Engineering of
relational as purchasing the business illustrated, that National School of Engineers of Tunis, Tunisia (e-mail: amel.touzi@
developed a commercial version of the Postgres system, an enit.rnu.tn, sassi_minyar@yahoo.fr).
A
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extended relational management system. Others big publishers III. OBJECT-REALATIONAL DATABASES CONCEPTION of management systems, as IBM and Oracle, followed this Methods of classic conception of relational databases evolution [1]-[2]-[7]-[8]. recommend to pass from E/A model (conceptual level) to a
normalized relational model (logical level), then to link on an A. Object-relational model principle
The object-relational model is founded on the idea of optimized relational model (internal level). Views are finally extension of the relational model with object concepts. declared (external level) according to prerogatives of users of
the data base. For the classic relational model, the passage User types and between every level makes them while respecting of precise encapsulation rules.
Conception process of an object-relational database,
described in Fig.2 inspires itself of the process of conception Inheritance Reference And reuse of a relational database [7]. and identity Real World
Collection and complex object
Fig.1 Relational model extension
An object-relational database is an extension of a relational Conceptual
level database. It unites the key concepts of the object to facilitate Merise, EA, UML, OMT, etc the integration of the two models. An object-relational SGBD
is a relational SGBD which will be added object
functionalities as the object identity, the encapsulation, the Navigational levelinheritance of types and the support of complex objects. This
is illustrated in Fig.1.
B. Essential Additional Concepts Internal
level We present in this section, additional concepts of object-Fig.2 Modeling process relational databases:
Process must follow the three steps: - User data types: user definite data type composed of a data
structure and operations encapsulates this structure. - The modeling of the real world according to a semantic The types system of the database management database E/A or UML formalism (conceptual level). becomes expandable and is not limited to the alphanumeric - The transposition of the conceptual diagram in a types of basis anymore. In this context, user must define its navigational model (logical level). types and to adapt those to the management of information. It - The transposition of the navigational diagram in types and becomes possible to define the picture types, point, vector, in object-relational tables of the object-relational databases etc. They are called Abstract Data Types (ADT). management systems (internal level). - Collection templates: generic data type permitting to support attributes multi-valuated and to organize them according to a
Until now, it doesn't exist software allowing the inventor to
collection type.
draw his E/A model or UML or navigational. Otherwise the
Bosses of lists permit to define some new types on the basis of
generation of the corresponding script in SQL3 language.
other type collections. They can use the different types of collections of the object-relational model, as table, list, set and
IV. NAVIGATIONAL MODEL dynamic tables.
- Reference of object: Particular data type permitting to
A. Presentation of the Navigational Model
memorize the invariant address of an object or a tuple.
Navigational term is used because this model includes References are identifiers of object (OID) of the object-relational model. They represent the unique and invariant drawers who facilitate the navigation between objects of the
values permitting of chaining objects between them without database. This model also proposes some notions as the types
of wholes, structures and references. The navigational model passing by joints by values [6]-[7]-[8]-[9].
- Inheritance of type: Shape of inheritance implying the plays a pivot role between the conceptual model and the possibility to define an under-type of an existing type, this one physical model. It facilitates the passage of an object inheriting the structure and the possible operations of the basis conceptual model to a model of object-relational database and
limits the risks of incoherence. Indeed, object approaches type.
- Inheritance of table: Shape of inheritance implying the permits to represent the complex data directly without possibility to define an under-table from existing tables, this necessary to normalize this information, but it is impossible to one inheriting the structure and the possible operations of the eliminate the problems caused by the non normalized objects. basis table.
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The normalization is not a specific concept to the relational systems, it is susceptible to concern all the structures of data. The navigational model can be considered like a theoretical support facilitating the passage of a conceptual model to an object-relational database model while limiting the risks of incoherence.
The abstract data types don't appear explicitly to the conceptual level. They are contained implicitly in the declaration of the entities (E/A) or of the classes (UML). Those types are clarified more in the navigational model.
The passage to the navigational model presented in Fig.4.
C_EmployéC_Département No NAS Nom Nas_Resp Nom Adresse T-adr Rue Dépendants CP B. Formalism of navigational diagram Ville The formalism of navigational diagram is very near to the formalism of Object Database Management Group (ODMG), T-depto which has been added the notions of identifying, of Prenom structure and intra-classes ties. The navigational model Sexe formalism permits to represent the static and dynamic aspects of classes.
Fig.4 Navigational model -Definitions: Classes contains some attributes (properties)
and signatures of methods (functions or procedures).
As the shows the diagram, we can modelize comfortably
Attributes can be simples (string, number,…), struct,
the composed attributes, multi-valuated attributes and
references (drawers), set (collection of structures or
drawers.
references) or of the previous type combinations. The ties can exist inside a same classes (intra-class) or
V. NAVIG-TOOLS
between two classes (inter-class).
In order to help understanding the stratification concept, we -Choice of the graphic representation of the ties: in a
navigational diagram, mono-valuated ties are represented by have built the tool NAVIG-TOOLS. This tool is plate-form
independent since it is developed with java. We chose arrows and multi-valuated ties by arrows with duplicate tip.
Oracle9i like database management system. Example:
The database organization has for goal to manage
NAVIG-TOOLS offer a convivial interface to the inventors of employees, departments of an enterprise.
An employee is described by identified Nas, a Name, an the object-relational databases that allow him:
-Modeling its conceptual Model in E/A and/or navigational Adresse composed by Rue, Cp and City and a dependant
described by last name and Sex. A department is described by model;
-Genering the corresponding SQL3 script;
identified number and name. A department is always managed
For every ambiguous steps, NAVIG-TOOLS propose to the
by only one employee.
inventor several solutions. Indeed, it is due to the fact that to
The E/A model of this database (presented in Fig.3)
represent a tie one can have several solutions [7].
contains two classes: the Employee class described by a In our first version of the software we limited ourselves to the simple attributes Nas and name, a composed attribute adresse types offered by the version oracel 9i, as: formed of three fields (Rue, CP, Ville) and a composed multi--Scalar Type (Number, Varchar, Date,..)
valuated attribute described by (Prenom and Sex). The class -Object Type Department described by simple attributes No, Nom and -Object Reference REF Responsable. -Collections (VARRAY and NESTED TABLE) Rue Ville CP NAVIG-TOOLS present to the expert a main screen (Fig.5)
similar to the standard usually used in the IDE (Integrated
Adresse NAS NomDevelopment Environment) and very similar to Power AMC
No Nom but to which one added new functionalities modeling the new symbols introduced by the navigational model and the new 0,1 1,1 concepts introduced by the object-relational databases
dirige Departement Employe concepts and the SQL3 language.
DependantPrenom SexFig.3 E/A model
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ClassInheritanceMulti-valuated tie Fig.5 NAVIG-TOOLS Interface
Fig.8 Generation of SQL3 Script
For implanting his database, the inventor must follow the two following steps:
1) Conception of database
The inventor can follow one of the three following methods:
- To draw the E/A model of his database as the shows the Fig.3. NAVIG-TOOLS can deduct the navigational model (Fig. 6). If the user is not satisfied, he can modify this model.
VI. CONCLUSION
In the next decade, the object-relational databases management systems will very certainly constitute one of the biggest technological progresses in databases domain. Mainly because they are construct on the bases of the relational technologies that gave its proofs since more of twenty years. It is for this reason, which we see that it is very important to think from now on one efficient tool for helping about the conception of object-reltional databases. As several of them exist for the relational databases and supporting the navigational model proposed by SOUTOU that showed its proofs. We proposed in this paper a tool of conception, called NAVIG-TOOLS that bring two main contributions to the conception and the implementation of the object-relational databases. The first improvement is that it offers to the user the possibility to draw the E/A and/or navigational models. The second is that it generated SQL3 script.
This work can be spread while proposing to test NAVIG-TOOLS on big database and to perfect our tools so that it can support the other types offered by the object-relational concepts.
REFERENCES
[1] P. Daehne, and P. Leutert, “Object and relational models”, High School
specialized of Switzerland Occidental, November 2001.
[2] A. Gamache, “Book on the databases \
and software genius, University Laval.
[3] E. Meylan, “Theoretical introduction to the object-relational model”,
High School specialized of Switzerland Occidental, June 2001. [4] C. SOUTOU, “Of UML in SQL“ , Eyrolles,2002.
[5] T. Quatrani, “Modélisation sur Rational Rose”, Eyrolles, 2000.
[6] G. Godin, “Database management systems by example”, Montréal,
Canada, 2003.
[7] C. SOUTOU,“Object - relational under Oracle 8. Modelling with UML
“ Eyrolles, 1999.
[8] R.G.G. Catell., “Object-Oriented Data Management: Object-Oriented
and Extended Relational Database Sytems”, Addison-Wesley Publishing, Inc., 1994.
[9] M. Makowski, “A structured modeling technology”, European Journal of
Operational Research, Vol. 166, Issue 3, 1 November 2005.
relational database (Fig.7). 2) Generation of SQL3 script
The inventor chosen the database management system menu, the button to generate the SQL3 script will be generated automatically by NAVIG-TOOLS (Fig.8).
- To draw directly the navigational model of its object-
Fig.6 E/A Model
Fig.7 Navigational Model
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