Development of an Assertion Model of Integrity Constraints in Object-Oriented Databases

Object-Oriented Databases (OODBs) have been designed to support large and complex programming projects. The data accuracy, consistency, and integrity in OODBs are extremely important for developers and users. Checking the integrity constraints in OODBs is a fundamental problem in database design. Existing OODB Management Systems (OODBMSs) lack to a capability of an ad-hoc declarative specification of enforcing and maintaining integrity constraints that are appeared among attributes in association, composition, and inheritance hierarchies' relationships. A critical problem in the existing OODBs is that they cannot support User-Defmed Constraints (UDCs) that can be defmed in classes with composition (logical or physical composition) and inherence (single or mUltiple inheritance) hierarchies. Integrity constraints in the current OODBMSs are maintained either by disallowing and rolling back transaction or modifying operations that may produce a violation. The constraints must be maintained in the backward direction along the class composition hierarchy as well as in the forward direction. In this work an Assertion Model of Integrity Constraints (AMIC) is proposed. The AMIC keeps the derivation path along with the attributes' relationships that are derived from association, composition, and inheritance hierarchies. The AMIC techniques are designed to implement the needed functions that are collecting the attributes' relationships and checking the integrity constraints. Moreover, AMIC keeps UDCs with their relationships in both single classes and multilevel classes (intra-class and inter-class). Furthermore, the AMIC can maintain constraints in a single object and a set of distributed objects (intra-object and inter-object). Therefore, this makes the new model extendable and can be integrated with any existing constraints' service. A new technique called Detection Method (DM) isdesigned to check the Object Meta Data (OMD) to detect the constraints violation before it occurs. The AMIC is designed for both Centralized Integrity Maintenance (CIM) and Application-Oriented Integrity Maintenance (AOIM). The AMIC can also enforce and maintain structural and logical integrity constraints, in addition to enforce and maintain redundant, inconsistent, and duplicate constraints

OODINI 2.1 : an enhanced graphical schema representation for object-oriented database

The graphical representation of an object-oriented database (OODB) schema is useful for the designers and users of a database system. The purpose of my thesis was to enhance the existing version of OOdini, an interactive graphical tool for editing an OODB schema. The new features include interactive modification and description of objects in the schema. Data structures for representing classes and attributes have been altered to incorporate object/data types as well as a descriptive string. The software has been implemented using the ObjectMaker toolkit to design our own methodology using the ObjectMaker Extension Language

Migrating relational databases into object-based and XML databases

Rapid changes in information technology, the emergence of object-based and WWW applications, and the interest of organisations in securing benefits from new technologies have made information systems re-engineering in general and database migration in particular an active research area. In order to improve the functionality and performance of existing systems, the re-engineering process requires identifying and understanding all of the components of such systems. An underlying database is one of the most important component of information systems. A considerable body of data is stored in relational databases (RDBs), yet they have limitations to support complex structures and user-defined data types provided by relatively recent databases such as object-based and XML databases. Instead of throwing away the large amount of data stored in RDBs, it is more appropriate to enrich and convert such data to be used by new systems. Most researchers into the migration of RDBs into object-based/XML databases have concentrated on schema translation, accessing and publishing RDB data using newer technology, while few have paid attention to the conversion of data, and the preservation of data semantics, e.g., inheritance and integrity constraints. In addition, existing work does not appear to provide a solution for more than one target database. Thus, research on the migration of RDBs is not fully developed. We propose a solution that offers automatic migration of an RDB as a source into the recent database technologies as targets based on available standards such as ODMG 3.0, SQL4 and XML Schema. A canonical data model (CDM) is proposed to bridge the semantic gap between an RDB and the target databases. The CDM preserves and enhances the metadata of existing RDBs to fit in with the essential characteristics of the target databases. The adoption of standards is essential for increased portability, flexibility and constraints preservation. This thesis contributes a solution for migrating RDBs into object-based and XML databases. The solution takes an existing RDB as input, enriches its metadata representation with the required explicit semantics, and constructs an enhanced relational schema representation (RSR). Based on the RSR, a CDM is generated which is enriched with the RDB's constraints and data semantics that may not have been explicitly expressed in the RDB metadata. The CDM so obtained facilitates both schema translation and data conversion. We design sets of rules for translating the CDM into each of the three target schemas, and provide algorithms for converting RDB data into the target formats based on the CDM. A prototype of the solution has been implemented, which generates the three target databases. Experimental study has been conducted to evaluate the prototype. The experimental results show that the target schemas resulting from the prototype and those generated by existing manual mapping techniques were comparable. We have also shown that the source and target databases were equivalent, and demonstrated that the solution, conceptually and practically, is feasible, efficient and correct

Making object-oriented databases more knowledgeable (From ADAM to ABEL)

Tesis leida en la Universidad de Aberdeen. 178 p.The salient points of this thesis are as follows: • Object-Oriented Databases can help in solving the impedance mismatch problem by introducing methods. However, methods have sometimes been overused in the sense th at the code encapsulated refers not only to how the operation is implemented but also to other kinds of knowledge that are implicit in the code. The disadvantages of this approach for modelling integrity constraints, user-defined relationships and active behaviour are pointed out. • The ADAM Object-Oriented Database has been extended to allow the designer to specify integrity constraints declaratively. A constraint equation approach is implemented th at supports the inheritance of constraints. • A need for semantic-rich user-defined relationships has been identified. In this thesis, relationships are represented as objects. An approach to enhance the semantics of relationships in both its structural and behavioural aspects is presented. The most novel idea of the approach presented is the support of the inferred properties and the operational semantics of relationships. • Active Databases have recently become an im portant area of research. This thesis shows how to extend an Object-Oriented Database with active capabilities. The principal contribution lies in representing as ‘first-class’ objects not only the active rules but also the rule manager itself. Hence, besides handling active rules as any other object in the system, future requirements can be supported just by specialising the current rule manager. • Active rules have been proposed for several purposes. Several examples, are given of the direct use of rules. However, higher level tools can be provided of which rule

The advantages and cost effectiveness of database improvement methods

Relational databases have proved inadequate for supporting new classes of applications, and as a consequence, a number of new approaches have been taken (Blaha 1998), (Harrington 2000). The most salient alternatives are denormalisation and conversion to an object-oriented database (Douglas 1997). Denormalisation can provide better performance but has deficiencies with respect to data modelling. Object-oriented databases can provide increased performance efficiency but without the deficiencies in data modelling (Blaha 2000). Although there have been various benchmark tests reported, none of these tests have compared normalised, object oriented and de-normalised databases. This research shows that a non-normalised database for data containing type code complexity would be normalised in the process of conversion to an objectoriented database. This helps to correct badly organised data and so gives the performance benefits of de-normalisation while improving data modelling. The costs of conversion from relational databases to object oriented databases were also examined. Costs were based on published benchmark tests, a benchmark carried out during this study and case studies. The benchmark tests were based on an engineering database benchmark. Engineering problems such as computer-aided design and manufacturing have much to gain from conversion to object-oriented databases. Costs were calculated for coding and development, and also for operation. It was found that conversion to an object-oriented database was not usually cost effective as many of the performance benefits could be achieved by the far cheaper process of de-normalisation, or by using the performance improving facilities provided by many relational database systems such as indexing or partitioning or by simply upgrading the system hardware. It is concluded therefore that while object oriented databases are a better alternative for databases built from scratch, the conversion of a legacy relational database to an object oriented database is not necessarily cost effective

A comprehensive part model and graphical schema representation for object-oriented databases

Part-whole modeling plays an important role in the development of database schemata in data-intensive application domains such as manufacturing, design, computer graphics. text document processing, and so on. Object-oriented databases (OODBs) have been targeted for use in such areas. Thus, it is essential that OODBs incorporate a part relationship as one of their modeling primitives. In this dissertation, we present a comprehensive OODB part model which expands the boundaries of OODB part-whole modeling along three fronts. First, it identifies and codifies new semantics for the OODB part relationship. Second, it provides two novel realizations for part relationships and their associated modeling constructs in the context of OODB data models. Third. it, provides an extensive graphical notation for the development of OODB schemata. The heart of the part model is a part relationship that imposes part-whole interaction on the instances of an OODB. The part relationship is divided into four characteristic dimensions: (1) exclusive/shared. (2) cardinality/ordinality, (3) dependency. and (A) value propagation. The latter forms the basis for the definition of derived attributes in a part hierarchy. To demonstrate the viability of our part model, we present two novel realizations for it in the context of existing OODBs. The first realizes the part relationship as an object class and utilizes only a basic set of OODB constructs. The second realization, an implementation of which is described in this dissertation, uses the unique metaclass mechanism of the VODAK Model Language (VML). This implementation shows that our part model can be incorporated into an existing OODB without having to rewrite a substantial subsystem of the OODB, and it also shows that the VML metaclass facility can indeed support extensions in terms of new semantic relationships. To facilitate the creation of part-whole schemata, we introduce an extensive graphical notation for the part relationship and its associated constructs. This notation complements our more general OODB graphical schema representation which includes symbols for classes, attributes. methods. and a variety of relationships. OO-dini, a graphical schema editor that employs our notation and supports conversion of the graphical schema into textual formats, is also discussed

Database Paradigms for Recordings Management

The relational database has long been considered the de facto standard for managing data in software applications. Today, a need for more scalable, flexible and distributed software solutions has led to the development of NoSQL database technologies that aim to replace the relational database in applications where such features are needed. In this thesis we have investigated the potential benefits of replacing SQLite, the database used by Axis Communications to manage recordings in their camera products, with a “Not only SQL” (NoSQL) database in an embedded camera system. To evaluate performance, test cases to measure execution times and resource consumption for database operations, based on important functionality in Axis’ storage solution, were designed. In the end the Embedded JSON Database Engine (EJDB) document database was identified. EJDB was found to be more efficient than SQLite at creating, updating and removing records. It was, however, less efficient when perform- ing queries based on conditional operators