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October 2003 |
Issue: 29 |
Editor's Corner
by Patrick Hallock
Uniqueness Constraints
on
Objectified
Associations
by Terry Halpin
Abstract: Unlike UML and some ER versions, ORM currently allows a fact type to be objectified only if it either has a spanning uniqueness constraint or is a 1:1 binary fact type. This article argues that this restriction should be relaxed, and replaced by a modeling guideline that allows some n-ary associations to be objectified even if their longest uniqueness constraint spans n-1 roles. The pros and cons of removing this restriction are discussed, and illustrated with examples.
The Chasing of Mayflies
Reply to Riggs
by Fabian Pascal
In the first editorial for the launch of DATABASE DEBUNKINGS, Skyscrapers with Shack Foundations, I wrote as follows:
In fact, under industry pressure there is little database education to be had. Product-specific training reigns supreme and even academic computer science programs are becoming increasingly vocational in character.
I repeated the argument in my second editorial, The Myth of Market-Based Education. Since then, I have demonstrated in at least one article, Denormalization for Performance – Et Tu Academia? that the academic state was actually sadder. That was further reinforced recently in an exchange with a faculty member from the University of Washington who, when I asked if there would be interest in presenting to their department, responded as follows:
Biological Data
and
Conceptual Modelling Methods
by C. Maria (Marijke) Keet
Abstract
The article highlights characteristics of biological data, and its effect on
conceptual modelling. Regarding biological data and its semantics, there is no
legacy to rely and build upon, there is an abundance of non-discrete data,
uncertainties on relevant parameters and a general lack of standardization in
nomenclatures and concepts.
General features of ER, OO and ORM are discussed, emphasising differences in graphical representation, understandability from the customer’s perspective and inclusiveness of types and attributes in the model. A second example, taxonomy, addresses (Extended-) OO, ad hoc solution POOM and the possibilities of FCA to formalize biological data and its concepts.
The more abstract conceptual modelling techniques ORM and FCA may be more promising in capturing the biological semantics as inclusive and formal as possible, in order to build-up an extensive repository and aid standardization, which in turn will improve the quality of developed software.
A Conceptual Modeling Technique
without
Redundant Structural Elements
by V.V.
Ovchinnikov
Conceptual modeling performs the key role during
realization of information system development projects. At present, there is a
quantify of conceptual modeling techniques, for instance, object-role modeling
technique which essence is shortly stated in the work.
Existent conceptual modeling
techniques have some disadvantages: ample quantity of equivalent representations
for a single universe of discourse (UoD); impossibility of conceptual query
formulating exclusively by means of UoD terms; necessity of additional knowledge
of relation using conditions and, as a result, insufficiency of knowledge of
interrelations between UoD terms for query formulating; some difficulty of model
familiarization for one who is not a specialist in the field of information
system designing. Enumerated disadvantages negatively influence on efficiency
and quality of designer's work, on speed and quality of communication among
project participants and, as a consequence, on quality of information system
being developed.
In the present paper, we introduce a
conceptual modeling technique, named semantically complete one, that is devoid
of the enumerated features; we produce analysis of its advantages and
disadvantages, and an example of its use in practice.
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