Andries Stam

Towards a language for coherent enterprise architecture descriptions

A coherent description of architectures provides insight, enables communication among different stakeholders and guides complicated (business and ICT) change processes. Unfortunately, so far no architecture description language exists that fully enables integrated enterprise modeling. In this paper we focus on the requirements and design of such a language. This language defines generic, organization-independent concepts that can be specialized or composed to obtain more specific concepts to be used within a particular organisation. It is not our intention to re-invent the wheel for each architectural domain: wherever possible we conform to existing languages or standards such as UML. We complement them with missing concepts, focusing on concepts to model the relationships among architectural domains. The concepts should also make it possible to define links between models in other languages. The relationship between architecture descriptions at the business layer and at the application layer (business-IT alignment) plays a central role.

Change impact analysis of enterprise architectures

An enterprise architecture is a high-level description intended to capture the vision of an enterprise integrating all its dimensions: organization structure, business processes, and infrastructure. Every single part of an enterprise is subject to change, and each change may have significant consequences within all domains of the enterprise. A lot of effort is therefore devoted to maintaining the integrity of an architectural description. In this paper we address the problem of mastering the ripple effects of a proposed change. This allows architects to assess the consequences of a particular change to the enterprise, in order to identify potential impacts of a change before it actually takes place.

Enterprise Architecture Analysis with XML

This paper shows how XML can be used for static and dynamic analysis of architectures. Our analysis is based on the distinction between symbolic and semantic models of architectures. The core of a symbolic model consists of its signature that specifies symbolically its structural elements and their relationships. A semantic model is defined as a formal interpretation of the symbolic model. This provides a formal approach to the design of architectural description languages and a general mathematical foundation for the use of formal methods in enterprise architectures. For dynamic analysis we define transformations of models of architectures, modeled in XML, and for this purpose the XML vocabulary for an architecture is extended with a few constructs defined in the Rule Markup Language (RML). There are RML tools available that perform the desired transformations.

Modeling and Testing Multi-Threaded Asynchronous Systems with Creol

Modeling concurrent systems and testing multi-threaded implementations against the model is an exciting field of study. This paper presents work done on constructing and executing test cases for an industrial-size multi-threaded application against a model written in the Creol modeling language. Models written in Creol, an object-oriented, concurrent modeling language, can be structurally similar to the finished implementation; we show how to keep this desirable property when re-using Creol models as test oracles. Also, a conformance relation between model and system under test that needs less controllability than other relations that are based on automata is presented.

Conformance Testing of Distributed Concurrent Systems with Executable Designs

This paper presents a unified approach to test case generation and conformance test execution in a distributed setting. A model in the object-oriented, concurrent modeling language Creol is used both for generating test inputs and as a test oracle. For test case generation, we extend Dynamic Symbolic Execution (also called Concolic Execution) to work with multi-threaded models and use this to generate test inputs that maximize model coverage. For test case execution, we establish a conformance relation based on trace inclusion by recording traces of events in the system under test and replaying them in the model. User input is handled by generating a test driver that supplies the needed stimuli to the model. An industrial case study of the Credo project serves to demonstrate the approach.

Credo Methodology

Credo offers tools and techniques to model and analyze highly reconfigurable distributed systems. In this paper, we present an integrated methodology to use the Credo tool suite. In this methodology, we advertise the use of top-down design, component-based modeling and compositional analysis to address the complexity of highly reconfigurable distributed systems. As a running example, we model a peer-to-peer file-sharing system and show how and when to apply the different modeling and analysis techniques of Credo.

Modeling and Analysis of Thread-Pools in an Industrial Communication Platform

Thread pools are often used as a pattern to increase the throughput and responsiveness of software systems. Implementations of thread pools may differ considerably from each other, which urges the need to analyze these differences in a formal manner. We use an object-oriented paradigm to model different thread pools in the context of the ASK system, an industrial communication platform. We use behavioral interfaces , high-level behavioral specifications for the objects, as a starting-point for analysis. Based on these behavioral interfaces, functional aspects are modeled in Creol, a high-level modeling language for concurrent objects. We use Uppaal to create real-time models and to perform schedulability analysis with respect to the behavioral interfaces. We finally check conformance between the real-time and Creol models using test-cases generated from the behavioral interfaces.

A logical viewpoint on architectures

We introduce a logical viewpoint on architectures. The logical viewpoint is based on the distinction between symbolic and semantic models of architectures. The core of a symbolic model consists of its signature that specifies symbolically its structural elements and their relationships. A semantic model is defined as a formal interpretation of the symbolic model. This leads to more precise characterization of the concepts introduced in IEEE standard 1471-2000, and provides a formal approach to the design of enterprise of architectural description languages and a general mathematical foundation for the use of formal methods in enterprise architectures. Additionally, we show how this logical viewpoint allows for the definition of a simple general XML language for the description of both static and dynamic aspects of an architecture. For the meta-analysis of both these aspects we introduce a new XML tool for general XML transformations based on a rule markup language.

Paradigm as Organization-Oriented Coordination Language

Global component behaviours as distinguished in Paradigm, offer the ingredients for specifying inter-component coordination in separation from and consistent with detailed component behaviour. The paper discusses how global behaviours provide great flexibility in arranging computation as well as coordination. In the context of a mediating example we plea for taking such flexibility as an organizational, organic, human-like characteristic; good to have, but usually absent in system specification. In addition, we point out how Paradigms flexibility fits well in the historical perspective of discrete event simulation, modeling, object-orientation and patterns.

Using XML transformations for enterprise architectures

In this paper we report on the use of XML transformations in the context of Enterprise Architectures. We show that XML transformation techniques can be applied to visualize and analyze enterprise architectures in a formal way. We propose transformational techniques to extract views from an XML document containing architectural information and indicate how to perform a specific form of impact analysis on this information. The transformations are formally expressed with the language RML, a compact yet powerful transformation language developed at CWI, which obtains its power from regular expressions defined on XML documents. We discuss a tool that has been built on top of it to visualize the results of the transformations and illustrate the advantages of our approach: the genericity of XML, the application of a single technique (namely XML transformations) for various tasks, and the benefits of having a model viewer which is in complete ignorance of the architectural language used.