TOWARDS MORE POWERFUL CONCEPTUAL SCHEMA LANGUAGES

One of the phases of information systems design methodologies is that of conceptual schema design. This phase involves identifying relevant objects, their properties and propositions involving these objects. These are described in a conceptual schema using a conceptual schema language. Conceptual schema languages which permit a graphical form are becoming more widely accepted under the motivation of being able to see the data structures that exist. However the semantics are somewhat limited with, for example, few integrity constraints being represented. In this paper we show how conceptual schema languages with a graphical form can be extended to permit a wider class of semantics to be represented

The Role of Application Domain Knowledge in Using OWL DL Diagrams: A Study of Inference and Problem-Solving Tasks

Diagrammatic conceptual schemas are an important part of information systems analysis and design. For effectively communicating domain semantics, modeling grammars have been proposed to create highly expressive conceptual schemas. One such grammar is the Web Ontology Language (OWL), which relies upon description logics (DL) as a knowledge representation mechanism. While an OWL DL diagram can be useful for representing domain semantics in great detail, the formal semantics of OWL DL places a burden on diagram users. This research investigates how user’s prior knowledge of the application domain impacts solving inference tasks as well as schema-based problem-solving tasks using OWL DL diagrams. Our empirical validation shows that application domain knowledge has no effect on inference performance but enhances schema-based problem-solving performance. We contribute to the conceptual modeling literature by studying task performance for a highly expressive modeling grammar and introducing inference tasks as a new task type

Towards Conceptual and Logical Modelling of NoSQL Databases

NoSQL databases support the ability to handle large volumes of data in the absence of an explicit data schema. On the other hand, schema information is sometimes essential for applications during data retrieval. Consequently, there are approaches to schema construction in, e.g., the JSON DB and graph DB communities. The difference between a conceptual and database schema is often vague in this case. We use functional constructs – typed attributes for a conceptual view of DB that provide a sufficiently structured approach for expressing semantics of document and graph data. Attribute names are natural language expressions. Such typed functional data objects can be manipulated by terms of a typed λ-calculus, providing powerful nonprocedural query features for considered data structures. The calculus is extendible. Logical, arithmetic, and aggregation functions can be included there. Conceptual and database modelling merge in this case

A layered view model for XML with conceptual and logical extensions, and its applications

University of Technology, Sydney. Faculty of Information Technology.EXtensible Markup Language (XML) is becoming the dominant standard for storing, describing and interchanging data among various Enterprises Information Systems (EIS), web repositories and databases. With this increasing reliance on such self-describing, schema-based, semi-structured data language XML, there exists a need to model, design, and manipulate XML and associated semantics at a higher level of abstraction than at the instance level. However, existing OO conceptual modelling languages provide insufficient modelling constructs for utilizing XML structures, descriptions and constraints, and XML and associated schema languages lack the ability to provide higher levels of abstraction, such as conceptual models that are easily understood by humans. To this end, it is interesting to investigate conceptual and schema formalisms as a means of providing higher level semantics in the context of XML-related data modelling. In particular we note that there is a strong need to model views of XML repositories at the conceptual level. This is in contrast to the situation for views for the relational model which are generally defined at the implementation level. In this research, we use XML view and introduce the Layered View Model (LVM, for short), a declarative conceptual framework for specifying and defining views at a higher level of abstraction. The views in the LVM are specified using explicit conceptual, logical and instance level semantics and provide declarative transformation between these levels of abstraction. For such a task, an elaborated and enhanced OO based modelling and transformation methodology is employed. The LVM framework leads to a number of interesting problems that are studied in this research. First we address the issue of conceptualizing the notion of views: the clear separation of conceptual concerns from the implementation and data language concerns. Here, the LVM views are considered as first-class citizens of the conceptual model. Second we provide formal semantics and definitions to enforce representation, specification and definition of such views at the highest level of abstraction, the conceptual level. Third we address the issue of modelling and transformation of LVM views to the required level of abstraction, namely to the schema and instance levels. Finally, we apply LVM to real-world data modelling scenarios to develop other architectural frameworks in the domains such as dimensional XML data modelling, ontology views in the Semantic Web paradigm and modelling user-centred websites and web portals

Translating Relational Conceptual Schema to Object-Oriented Schema

A multidatabase is a confederation of preexisting distributed, heterogeneous, and autonomous database system. The integration process is essential in the effort of forming a distributed, heterogeneous database system. This process generally consists of two main phases, which are conceptual schema translation phase and followed by the integration phase. In our research, we have proposed an alternative translation approach to convert relational database schema to object--oriented database schema. The translation approach consists of a set of translation rules, which are based on inclusion dependencies, key attributes and types of attributes. A database schema translation tool prototype, called RETOO (Relational-to-Object-Oriented) is then developed based on the proposed translation approach. RETOO receives a relational database schema as input data and generate an object-oriented database schema as the output data.RETOO operates semi-automatically, especially in the process of identifying operations for each class. This is because relational data model does not provide the behavioural information of every entity. The translation approach and RETOO database translation tool prototype are not only able to maintain the semantics of the relational database schema, but also enhance the semantics of the translated object-oriented schema via object-oriented data modelling concepts

An Experimental Study of the Effects of Representing Property Precedence on the Comprehension of Conceptual Schemas

Conceptual modeling is the process of using a grammar to construct abstractions of relevant phenomena in a domain. The resulting conceptual schemas are intended to facilitate understanding of and communication about a domain during information systems requirements analysis and during design. Despite keen practitioner interest in conceptual modeling, there is general agreement that the modeling constructs comprising grammars lack theoretical foundations pertaining to what the constructs are intended to represent, which, in turn, inhibits our understanding of whether and why they are effective. This research contributes to our understanding of conceptual modeling grammars by proposing a theoretically-grounded approach for modeling an important aspect of the nature of properties of the phenomena of interest in a domain. Specifically, conceptual schemas typically fail to express explicitly the semantics that, when things possess particular properties, they must also possess certain other properties. This research uses Bunge’s ontological notion of property precedence as the theoretical rationale for explicitly modeling this dependence in conceptual schema diagrams. We examine several forms of precedence, and propose an approach to representing one form in conceptual schemas. We present the results of a laboratory experiment that tests the impact of explicitly representing precedence on how well participants comprehend the semantics conveyed by a conceptual schema. The results indicate that modeling precedence explicitly improves the comprehension of domain semantics expressed in a diagram’s structure, but has varying effects on subjects’ confidence in their comprehension

Alternative representations for visual constrainst specification in the layered view model

Extensible Markup Language (XML), with its rich set of semantics and constraints, is becoming the dominant standard for storing, describing and interchanging data among various Enterprises Information Systems (EIS) and databases. With the increased reliance on such semi-structured data and schemas, there exists a requirement to model, design, and constrain semi-structured data and the associated semantics at a higher level of abstraction than at the instance or data level. But most semi-structured schema languages lack the ability to provide higher levels of abstraction, such as visual constraints, that are easily understood by humans. Conversely, though Object-Oriented (OO) conceptual models offers the power in describing and modelling real-world data semantics, constraints and their inter-relationships in a form that is precise and comprehensible to users, they provide insufficient modelling constructs for utilizing XML schema like data descriptions and constraints. Therefore, it is interesting to investigate conceptual and schema formalisms as a means of providing higher level semantics in the context of XML-related data engineering. In this paper, we present a visual constraint specification model for an XML layered view model. First we briefly outline the view model and then provide a detailed discussion on modelling issues related to view constraint specification using two OO modelling languages, namely OMG's UML/OCL and XML Semantics (XSemantic) nets. To demonstrate our concepts, we also provide an illustrative case study example based on a real-world application

XML views, part III: An UML based design methodology for XML views

Object-Oriented (OO) conceptual models have the power in describing and modelling real-world data semantics and their inter-relationships in a form that is precise and comprehensible to users. Today UML has established itself as the language of choice for modelling complex enterprises information systems (EIS) using OO techniques. Conversely, the eXtensible Markup Language (XML) is fast emerging as the dominant standard for storing, describing and interchanging data among various enterprises systems and databases. With the introduction of XML Schema, which provides rich facilities for constraining and defining XML content, XML provides the ideal platform and the flexibility for capturing and representing complex enterprise data formats. Yet, UML provides insufficient modelling constructs for utilising XML schema based data description and constraints, while XML Schema lacks the ability to provide higher levels of abstraction (such as conceptual models) that are easily understood by humans. Therefore to enable efficient business application development of large-scale enterprise systems, we need UML like models with rich XML schema like semantics. To address such issue, in this paper, we proposed a generic, semantically rich view mechanism to conceptually model and design (using UML) XML domains to support data modelling of complex domains such as data warehousing and e-commerce systems. Our approach is based on UML and UML stereotypes to design and transform XML views

ADS Formal Semantics

Abstract Database System (ADS) is a data model developed for an enduring medical information system where frequent changes in the conceptual schema are anticipated and multi-level abstraction is required. The mechanism of abstraction in ADS is based on the abstraction operator of the lamba calculus. The formal semantics of a subset of the ADS model is presented using the denotational specification method

A refined architecture for terminological systems : terminology = schema + views

Traditionally, the core of a Terminological Knowledge Representation System (TKRS) consists of a TBox, where concepts are introduced, and an ABox, where facts about individuals are stated in terms of concept memberships. This design has a drawback because in most applications the TBox has to meet two functions at a time: On the one hand - similarly to a database schema - frame-like structures with type information are introduced through primitive concepts and primitive roles; on the other hand, views on the objects in the knowledge base are provided through defined concepts. We propose to account for this conceptual separation by partitioning the TBox into two components for primitive and defined concepts, which we call the schema and the view part.We envision the two parts to differ with respect to the language for concepts, the statements allowed, and the semantics. We argue that this separation achieves more conceptual clarity about the role of primitive and defined concepts and the semantics of terminological cycles. Three case studies show the computational benefits to be gained from the refined architecture