Stephen J. Mellor Quotes

13 Sourced Quotes

While a small domain (consisting of fifty or fewer objects) can generally be analyzed as a unit, large domains must be partitioned to make the analysis a manageable task. To make such a partitioning, we take advantage of the fact that objects on an information model tend to fall into clusters: groups of objects that are interconnected with one another by many relationships. By contrast, relatively few relationships connect objects in different clusters.
When partitioning a domain, we divide the information model so that the clusters remain intact... Each section of the information model then becomes a separate subsystem. Note that when the information model is partitioned into subsystems, each object is assigned to exactly one subsystem.

Stephen J. Mellor
I was astonished to be invited to what became the meeting that originated the Agile Manifesto because my work had always been based around building models... The other signatories were kind enough, back in 2001, to write the manifesto using the word software (which can include executable models), not code (which is more specific.) As such I felt able, in good conscience, to become a signatory to the Manifesto while continuing to promote executable modeling. Ten years on we have a standard action language for agile modeling.

Stephen J. Mellor
Executable UML is one pillar supporting the Model-Driven Architecture (MDA) initiative, the purpose of which is to enable specification of systems using models.

Stephen J. Mellor
Executable UML is designed to produce a comprehensive and comprehensible model of a solution without making decisions about the organization of the software implementation. It is a highly abstract thinking tool to aid in the formalization of knowledge, a way of thinking about and describing the concepts that make up an abstract solution to a client problem.

Stephen J. Mellor
What's really going on is that Executable UML is a concurrent specification language.

Stephen J. Mellor
Executable UML is at the next higher layer of abstraction, abstracting away both specific programming languages and decisions about the organization of the software so that a specification built in Executable UML can be deployed in various software environments without change.

Stephen J. Mellor
Executable UML is an abstract object-oriented formalism; hence, it employs classes, attributes, and other object-oriented constructs as a way to organize abstractions.

Stephen J. Mellor
What's the point of having metamodels, and why should you care? Because models must be stated in a way that yields a common understanding among all involved parties, we need a way to specify exactly what a model means. Metamodels allow you to do just that: They specify the concepts of the language you're using to specify a model.

Stephen J. Mellor
We build models to increase productivity, under the justified assumption that it's cheaper to manipulate the model than the real thing. Models then enable cheaper exploration and reasoning about some universe of discourse. One important application of models is to understand a real, abstract, or hypothetical problem domain that a computer system will reflect. This is done by abstraction, classification, and generalization of subject-matter entities into an appropriate set of classes and their behavior.

Stephen J. Mellor
An object in OOA represents a single typical but unspecified instance of something in the real world - any airplane, I don't care which one, as long as it is typical. The object-oriented analyst distinguishes this concept from that of a specified instance: Airplane number N2713A, Air Force One, or The Spirit of St. Louis, for example.

Stephen J. Mellor
Executable UML is careful to distinguish the concept of a model, the underlying data, behavior or computation, from its representation. The representation is typically a diagram or a table, though it could be any representation you can image.

Stephen J. Mellor
MDA per se is relaxed about exactly what models it transforms, so long as the modeling language in which the models are expressed can be defined.

Stephen J. Mellor
In the bad old days before MDA, (conceptual) models served only to facilitate communication between customers and developers and act as blueprints for construction. Nowadays, MDA establishes the infrastructure for defining and executing transformations between models of various kinds.

Stephen J. Mellor