H.A. Proper

Conceptual schemas with abstractions making flat conceptual schemas more comprehensible

Abstract Flat graphical, conceptual modeling techniques are widely accepted as visually effective ways in which to specify and communicate the conceptual data requirements of an information system. Conceptual schema diagrams provide modelers with a picture of the salient structures underlying the modeled universe of discourse, in a form that can readily be understood by and communicated to users, programmers and managers. When complexity and size of applications increase, however, the success of these techniques in terms of comprehensibility and communicability deteriorates rapidly. This paper proposes a method to offset this deterioration, by adding abstraction layers to flat conceptual schemas. We present an algorithm to recursively derive higher levels of abstraction from a given (flat) conceptual schema. The driving force of this algorithm is a hierarchy of conceptual importance among the elements of the universe of discourse.

Query Formulation as an Information Retrieval Problem

Query formulation in the context of large conceptual schemata is known to be a hard problem. When formulating ad hoc queries users may become overwhelmed by the vast amount of information that is stored in the information system; leading to a feeling of lost in conceptual space. In this article we develop a strategy to cope with this problem. This strategy is based on ideas from the information retrieval world, in particular the query by navigation mechanism and the stratified hypermedia architecture. The stratified hypermedia architecture is used to describe the information contained in the information system on multiple levels of abstraction. When using our approach to the formulation of queries, a user will first formulate a number of simple queries corresponding to linear paths through the information structure. The formulation of the linear paths is the result of the explorative phase of query formulation. Once users have specified a number of these linear paths, they may combine them to form more complex queries. This last process is referred to as query by construction and corresponds to the constructive phase of the query formulation process.

Data schema design as a schema evolution process

In an information system a key role is played by the underlying data schema. This article starts out from the view that the entire modelling process of an information systems data schema can be seen as a schema transformation process. A transformation process that starts out with an initial draft conceptual schema and ends with an internal database schema for some implementation platform. This allows us to describe the transformation process of a database design as an evolution of a schema through a universe of data schemas. Doing so, allows for a better understanding of the actual design process, countering the problem of software development under the lamppost. Even when the information system design is finalised, the data schema can evolve further due to changes in the requirements on the system. We present a universe of data schemas that allows us to describe the underlying data schemas at all stages of their development. This universe of data schemas is used as a case study on how to describe the complete evolution of a data schema with all its relevant aspects. The theory is general enough to cater for more modelling concepts, or different modelling approaches. To actually model the evolution of a data schema, we present a versioning mechanism that allows us to model the evolutions of the elements of data schemas and their interactions, leading to a better understanding of a schema design process as a whole. Finally, we also discuss the relationship between this simple versioning mechanism and general purpose version management systems.

A generic model for 3-dimensional conceptual modelling

Abstract This article discusses two highly intertwined issues. Firstly, we discuss the lack of top-down abstraction mechanisms in data modelling techniques; i.e. abstraction techniques that are fully integrated into the modelling technique and methodology and not just a ‘post-modelling process’ add on. Secondly, we are concerned with the integration of object-oriented modelling techniques and traditional data modelling techniques. We start by discussing the pragmatics and motivations behind these issues. Then, a formalisation of (the syntax and semantics of) a data modelling technique is presented that is a generalisation of (E)ER and ORM, and also adheres to the requirements of an object-oriented technique as laid down in the object-oriented manifesto. The result of this exercise is the so-called CDM Kernel. Furthermore, we briefly show how (E)ER, ORM and object-oriented views can be derived from models in the CDM Kernel. This effectively means that the CDM Kernel equates (E)ER, ORM and (some) object-oriented models. Finally, we briefly discuss some practical issues on the use of the facilities offered by the CDM Kernel in terms of modelling practice and tool support. A generalised conceptual modelling kernel will be very beneficial in the context of CASE Tool and in the context of federated database (information) systems.

Towards Real-Scale Business Transaction Workflow Modelling

While the specification languages of workflow management systems focus on process execution semantics, the successful development of workflows relies on a fuller conceptualisation of business processing including the treatment of time, document transfer, and workflow use and reuse. For this, a wellspring of modelling techniques, paradigms and informal-formal method extensions which address broader enterprise modelling and communication (based on speech-act theory), is available. However, the characterisations — indeed the cognition — of workflows still appears coarse. In this paper, we provide the complementary, empirical insight of a real-scale business transaction workflow. The development of the workflow model follows a set of principles which we believe address workflow modelling suitability. Through the principles, advanced considerations including temporal constraints, message construction and deconstruction together with asynchronous and synchronous modes of messaging, service encapsulation, and complex decision and exception handling are motivated. By illustrating the suitability principles and with it the inherent complexity of business transaction domains, we offer timely insights into workflow specification extension.