Object-oriented Database Schema Research Articles

Uncertainty Modeling of Object-Oriented Biomedical Information in HBase

While object-oriented databases (OODBs) are known to be rich in functionality, HBase database, which is a distributed and scalable big data store, as well as uncertain databases have recently gained a lot of attention in the database community. This paper presents a methodology for handling an important step of knowledge integrations and migrations. In particular, a formal approach for reengineering fuzzy object-oriented databases in HBase is firstly developed. The reengineering approach is based on the technique of rule-based schema mapping, which defines a set of transformation rules involved in the process of schema transformations for mapping a fuzzy object-oriented database schema into a fuzzy HBase database schema. In addition, a formal approach to map the fuzzy object-oriented algebra into fuzzy HBase algebra is proposed. On this basis, we complement the work with a comprehensive set of experiments to show the efficiency of our proposed approach in terms of query time and scalability metrics.

Towards Comparative Mining of Web Document Objects with NFA

The process of extracting comparative heterogeneous web content data which are derived and historical from related web pages is still at its infancy and not developed. Discovering potentially useful and previously unknown information or knowledge from web contents such as “list all articles on ’Sequential Pattern Mining’ written between 2007 and 2011 including title, authors, volume, abstract, paper, citation, year of publication,” would require finding the schema of web documents from different web pages, performing web content data integration, building their virtual or physical data warehouse before web content extraction and mining from the database. This paper proposes a technique for automatic web content data extraction, the WebOMiner system, which models web sites of a specific domain like Business to Customer (B2C) web sites, as object oriented database schemas. Then, non-deterministic finite state automata (NFA) based wrappers for recognizing content types from this domain are built and used for extraction of related contents from data blocks into an integrated database for future second level mining for deep knowledge discovery.

Contextual Partitioning for Comprehension of OODB Schemas

Object-oriented databases (OODBs) have been utilized for complex modeling tasks within a variety of application domains. The OODB schema, typically expressed in a graphical notation, can serve as a useful presentation tool for the information contained in the underlying OODB. However, such a schema can be a large, complex network of classes and relationships. This may greatly hinder its effectiveness in helping users gain an understanding of the OODB’s contents and data organization. To facilitate this orientation process, a theoretical framework is presented that guides the refinement\/ of an existing schema’s subclass-of\/ relationship hierarchy – the backbone of any OODB. The framework sets forth three rules which, when satisfied, lead to the establishment of a collection of contexts, each of which exhibits an internal subclass-of\/ tree structure. A formal proof of this result is presented. An algorithmic methodology, involving a human–computer interaction, describes how the approach can be applied to a given OODB schema. An application of the methodology to an example OODB schema is included.

Enhancing OODB semantics to support browsing in an OODB vocabulary representation

AbstractIn previous work, we have modeled a vocabulary given as a semantic network by an object‐oriented database (OODB). The OODB schema thus obtained provides a compact abstract view of the vocabulary. This enables the fast traversal of the vocabulary by a user. In the semantic network vocabulary, the IS‐A relationships express the specialization hierarchy. In our OODB modeling of the vocabulary, the SUBCLASS relationship expresses the specialization hierarchy of the classes and supports the inheritance of their properties. A typical IS‐A path in the vocabulary has a corresponding shorter SUBCLASS path in the OODB schema.In this paper we expose several cases where the SUBCLASS hierarchy fails to fully correspond to the IS‐A hierarchy of the vocabulary. In these cases there exist traversal paths in the semantic network for which there are no corresponding traversal paths in the OODB schema. The reason for this failure is the existence of some IS‐A relationships between concepts of two classes, which are not connected by a SUBCLASS relationship. This phenomenon weakens the accuracy of our modeling.To rectify the situation we introduce a new OODB semantic relationship IS‐A$'$ to represent the existence of IS‐A relationships between concepts of a pair of classes which are not connected via a SUBCLASS relationship. The resulting schema contains both SUBCLASS relationships and IS‐A$'$ relationships which completely model the IS‐A hierarchy of the vocabulary. We define a mixed‐class level traversal path to contain either SUBCLASS or IS‐A$'$ relationships. Consequently, each traversal path in the semantic network has a corresponding mixed traversal path in the OODB schema. Hence the introduction of the semantic OODB IS‐A$'$ relationship improves the modeling of semantic network vocabularies by OODBs. Copyright © 2003 John Wiley & Sons, Ltd.

객체모델을 이용한 XML DTD의 OODB 스키마로의 변환

B2B 전자상거래와 같이 XML.을 이용한 정보교환이 확산되고 있으며 이에 따라 상호 교환되는 정보에 대하여 체계적이며 안정적인 저장관리가 요구되고 있다. 이를 위해 XML 응용과 데이터베이스 연계를 위한 다양한 연구가 관계형 데이터베이스를 중심으로 수행되었다. 그러나 계층구조를 갖는 XML 데이터를 2차원 테이블의 집합인 관계형 정보로 표현하는 관계형 데이터베이스로의 저장에는 본질적인 한계가 있어, 계층구조를 지원하는 객체지향 데이터베이스로의 저장이 요망된다. 이에 따라 계층구조를 갖는 XML 데이터를 객체지향 데이터 베이스로 지장하기 위한 모델링 방안이 요구된다. 본 논문에서는 객체모델을 토대로 DTD를 객체 지향 데이터베이스 스키마로 변환하기 위한 방법을 제안한다. 이를 위하여 먼저 DTD를 객체모델로 변환시키기 위한 객체변환 방안을 제시하고, 변환된 객체모델을 객체지향 데이터베이스 스키마로 변경시키기 위한 스키마 변환 방법을 제안했다. Information exchange on XML such as B2B electronic commerce is spreading. Therefore the systematic and stable management mechanism for storing the exchanged information is needed. For this goal there are many research activities for connection between XML application and relational database. But because XML data have hierarchical structures and relational database can store only flat-structured data, we need to store XML data in object-oriented database that support hierarchical structure. Accordingly the modeling methodology for storing XML data in object-oriented database is needed. In this parer, the transforming methods based on object model from XML DTD to object-oriented database schema is proposed. For this, we first introduce mapping methods that map XML DTD to object model and then we propose soem methods that transform from the object model to object-oriented database schema.

Finite satisfiability of integrity constraints in object-oriented database schemas

Checking satisfiability of database constraints is a fundamental problem in database design. In addition, database constraints have to be not only satisfiable but also finitely satisfiable. This problem is generally addressed by using theorem provers that, being developed for first order logic formulas, are based on semidecidable procedures. Furthermore, even in simple cases, theorem provers are quite inefficient in dealing with comparison operators such as, for instance, the equality. In this paper, a decidable, sound, and complete method for checking finite satisfiability of a specific class of integrity constraints for object-oriented databases, including the equality constraints, is presented. The method, that is based on a graph-theoretic approach, has exponential complexity in the worst case, rarely occurring in practice.

The Goql Graphical Query Language

The authors present a graphical query language, GOQL (Graphical Object Query Language), for object-oriented data base systems, in general, and the object model of ODMG 2.0, in particular. A detailed literature survey of related work is given, and an analysis methodology that allows the evaluation of such languages is proposed. Moreover, the user's view of GOQL is presented. The user's view provides a graphical schema that does not contain any of the perplexing details of an object-oriented database schema; it also provides a graphical interface that supports ad hoc queries for object-oriented database applications. Because there is a direct correspondence between the features of GOQL and OQL (GOQL supports all the features of OQL), the language can be used as an alternative graphical interface to OQL. Thus, GOQL allows users to express queries graphically ranging from simplistic to complicated ones. Among the features provided/supported by the language are: a 2D colour interface, methods, predicates, Boolean and set operators, arithmetic expressions, existential/universal quantifiers, aggregate functions, group by and sort operators, functions, and subqueries. In this article, we illustrate through examples both the user's view and the query mechanism of GOQL. This work represents the completion of work that was partially presented in earlier articles.

Refinements of Complexity Results on Type Consistency for Object-Oriented Databases

The method invocation mechanism is one of the essential features in object-oriented programming languages. This mechanism contributes to data encapsulation and code reuse, but there is a risk of a run-time type error. In the case of object-oriented databases (OODBs), a run-time error causes rollback. Therefore, it is desirable to ensure that a given OODB schema is consistent; i.e., no run-time type error occurs during the execution of queries under any database instance of the OODB schema. This paper discusses the computational complexity of the type-consistency problem. As a model of OODB schemas, we adopt update schemas introduced by R. Hull et al., which have all of the basic features of OODBs such as class hierarchy, inheritance, and complex objects. For several subclasses of update schemas, the complexity of the type-consistency problem is presented. Importantly, it turns out that nonflatness of the class hierarchy, recursion in the queries, and update operations in the queries each make the problem difficult.

An object-oriented database design for improved performance

Object-oriented databases (OODBs) are known to be rich in functionality but poor in performance. One of the important factors that affect performance is the physical database design. We developed a methodology for the design of an efficient storage structure of OODB that minimizes the database operating costs. The input for our method is the logical OODB schema and set of user transactions of retrieval and update types. The output of our method is the determination of which instance variables should be inherited from direct and indirect superclasses and stored in which subclasses. We used a genetic algorithm (GA) to solve this intractable problem. The methodology was applied on a university database. Compared to previous storage models, the storage model produced with our methodology showed database performance improvement ranging from 26% to 31%, on the average. Our results demonstrate a cost-effective storage structure design that boosts the operating performance of OODBs.

An empirical investigation of factors influencing object-oriented database querying

Object-oriented databases (OODBs) provide an effective means for capturing complex data and semantic relationships underlying many real-world database applications. Because users' interactions with databases have increased significantly in today's era of client–server computing, it is important to examine users' ability to interact with such databases. We investigated a number of factors that potentially affect performance in writing queries on an OODB. First, we evaluated the utility of graphical and textual schemas associated with emerging OODBs from the perspective of database querying. Second, we examined the use of two different strategies (navigation and join) that could be used in writing OODB queries. Third, we examined a number of factors that potentially contribute to the complexity of an OODB query. Our exploratory study examined the performance of 20 graduate students in an experiment in which each participant wrote queries for two problems, one using a graphical OODB schema and the other a textual OODB schema. The participants had no prior exposure to the object-oriented data model. We found that there was no difference in query writing performance (either accuracy or time) using the graphical and textual schemas. Examination of query strategy revealed that a significant number of participants used a join strategy, rather than the navigation strategy that matches the database structure. Use of the join strategy resulted in significantly less accurate and slower query writing than did the navigation strategy. From the viewpoint of complexity, the number of objects referenced in a query, the number of starting points in the “from” clause, and the presence of special operators influenced both the accuracy and time of query writing.

Conceptual design of fuzzy object-oriented databases using extended entity-relationship model

Entity-relationship–extended entity-relationship models play a crucial role in the conceptual design of relational databases as well as object-oriented databases. Recently, several approaches have been proposed to enhance object-oriented databases (OODBs) using fuzzy set theory. In this paper, we introduce a fuzzy extended entity-relationship model to cope with imperfect as well as complex objects in the real world at a conceptual level. In particular, we provide the formal approach to mapping a fuzzy extended entity-relationship model to a fuzzy object-oriented database schema. © 2001 John Wiley & Sons, Inc.

View integration of behavior in object-oriented databases

Database schemas are often not defined by a single person but by several future users of the database who define their possibly different views on the proposed database schema. These views are collected and integrated during the subsequent design step of view integration. In object-oriented databases, view integration must handle the integration of the structure and the behavior of objects. Whereas integration of object structure has been treated in the realm of semantic data models in the past, integration of object behavior has received little attention so far. Behavior is usually defined at two levels of detail: by activities, which correspond to methods in object-oriented languages, and by object life-cycles, which represent the overall behavior of objects during their life time. This paper presents an approach to integrate object life-cycles in object-oriented database schemas using a notation based on Petri nets. We will introduce different methods of integration depending on identified semantic correspondences between the object types in the views.

Representing the UMLS as an object-oriented database: modeling issues and advantages.

The Unified Medical Language System (UMLS) combines many well-established authoritative medical informatics terminologies in one knowledge representation system. Such a resource is very valuable to the health care community and industry. However, the UMLS is very large and complex and poses serious comprehension problems for users and maintenance personnel. The authors present a representation to support the user's comprehension and navigation of the UMLS. An object-oriented database (OODB) representation is used to represent the two major components of the UMLS-the Metathesaurus and the Semantic Network-as a unified system. The semantic types of the Semantic Network are modeled as semantic type classes. Intersection classes are defined to model concepts of multiple semantic types, which are removed from the semantic type classes. The authors provide examples of how the intersection classes help expose omissions of concepts, highlight errors of semantic type classification, and uncover ambiguities of concepts in the UMLS. The resulting UMLS OODB schema is deeper and more refined than the Semantic Network, since intersection classes are introduced. The Metathesaurus is classified into more mutually exclusive, uniform sets of concepts. The schema improves the user's comprehension and navigation of the Metathesaurus. The UMLS OODB schema supports the user's comprehension and navigation of the Metathesaurus. It also helps expose and resolve modeling problems in the UMLS.

A hybrid approach to convert relational schema to object-oriented schema

In the paradigm of DataBase Re-Engineering (DBRE), reverse-engineering data semantics by schema translation from lower level of abstraction such as relational schema to a higher level of abstraction such as Extended Entity Relational (EER) model has been, in the past, extensively studied with due to its relative simplicity in matching. However, schema transformation from EER model to Object-Oriented DataBase (OODB) schema is not straightforward due to its missing of dynamic semantic representation, since an Object-Oriented (OO) schema should contain both the structure and operations of the data objects. In this paper, we describe a hybrid approach which applies both heuristic learning techniques in discovering the behavioural semantics from relational schema and knowledge-based approach in recovering static and structural semantics, to reach a complete conversion. A practical case is applied through an implemented prototype to validate the effectiveness of our methodology.

A data model and a query languagefor multimedia documents databases

A multimedia application involves information that may be in a form of video, images, audio, text and graphics, need to be stored, retrieved and manipulated in large databases. In this paper, we propose an object-oriented database schema that supports multimedia documents and their temporal, spatial and logical structures. We present a document example and show how the schema can adress all the structures described. We also present a multimedia query specification language that can be used to describe a multimedia content portion to be retrieved from the database. The language provides means by which the user can specify the information on the media as well as the temoral and spatial relationships among these media.

Object-oriented evolutionary database design for software metrics data

The authors present an approach to manage evolutionary changes that take place over time in an object-oriented software metrics database schema. The framework is based on the entity-relation (E-R) model and uses a recursive graph structure, known as R-graph, to support the views of software quality and risk. The fundamental mechanism for abstracting views is the introduction of two semantic operators for the R-graph. These operators are proposed based on graph-based predicates and Petri-net based predicate formalism for view abstraction.

Transforming RDB schema into well-structured OODB schema

When transforming relational database (RDB) schema into object-oriented database(OODB) schema, much effort was put on examining key and inclusion dependency (ID) constraints to identify class and establish inheritance and association between classes. However, in order to further remove the original data redundancy and update anomaly, multi-valued dependency (MVD) should also be examined. In this paper, we discuss class structures and define well-structured classes. Based on MVDs, a theorem is given transforming a relation schema into a well-structured class. To transform RDB schema into OODB schema, a composition process simplifying the input RDB schema and an algorithm transforming the simplified RDB schema into well-structured OODB classes are developed.

A computerised calibration service supporting system. I: System design and development

A computerised calibration service supporting system (CCSS) is developed to assist the calibration procedure by easy accessing of the service and customers' databases. The calibration service procedure is modelled using IDEF0 method, which depicts the process flow of the calibration service. Based on the required data types of the process flow, an EXPRESS data model is defined for the system. This data model is used to construct both the application class lattice and object-oriented database schema. The system implementation follows the STEP enabling information system development procedure. The procedure includes process modelling, data modelling, object class building (C++), and programming of the decision support system integrated with the database for instanced object populations. This system takes advantages of calibration data management and decision supports through a web interface, and provides the calibration centre, a computerised tool to serve its customers efficiently and effectively.

Using architectural forms to map TEI data into an object-oriented database

This paper develops a solution to the problem of importing existing TEI data into an existing object-oriented database schema without changing the TEI data or the database schema. The solution is based on architectural processing. Two meta-DTDs are used, one to define the architectural forms for the object model and another to map the existing SGML data onto those forms. A full example using a critical text in TEI markup is developed.

Inheritance hierarchy design in object-oriented databases

Object-oriented database schema design is still mostly an art. One of the difficulties encountered during design is typing conflicts induced by multiple inheritance. In this paper, we propose a method for treating such a kind of conflicts. Our approach to inheritance conflict solving consists of several ingredients. First, we rely on branding, to introduce ‘type equivalence by name’, thus allowing a designer to distinguish between structurally similar but se-mantically different types. However, we offer a heuristic that does not require a designer to explicitly state branding declarations. Second, we describe various kinds of conflicts, and we offer a set of procedures that analyze a schema to discover such conflicts, classify them, offering potential solutions, if possible. The procedures have been conceived for a design system that allows a designer maximum flexibility, while guiding him/her to a correct design.