Towards a design-by-contract based approach for realizable connector-centric software architectures

Despite being a widely-used language for specifying software systems, UML remains less than ideal for software architectures. Architecture description languages (ADLs) were developed to provide more comprehensive support. However, so far the application of ADLs in practice has been impeded by at least one of the following problems: (i) advanced formal notations, (ii) lack of support for complex connectors, and (iii) potentially unrealizable designs. In this paper we propose a new ADL that is based on Design-by-Contract (DbC) for specifying software architectures. While DbC promotes a formal and precise way of specifying system behaviours, it is more familiar to practising developers, thus allowing for a more comfortable way of specifying architectures than using process algebras. Furthermore, by granting connectors a first-class status, our ADL allows designers to specify not only simple interaction mechanisms as connectors but also complex interaction protocols. Finally, in order to ensure that architectural designs are always realizable we eliminate potentially unrealizable constructs in connector specifications (the connector “glue”)

Interacting Components

SystemCSP is a graphical modeling language based on both CSP and concepts of component-based software development. The component framework of SystemCSP enables specification of both interaction scenarios and relative execution ordering among components. Specification and implementation of interaction among participating components is formalized via the notion of interaction contract. The used approach enables incremental design of execution diagrams by adding restrictions in different interaction diagrams throughout the process of system design. In this way all different diagrams are related into a single formally verifiable system. The concept of reusable formally verifiable interaction contracts is illustrated by designing set of design patterns for typical fault tolerance interaction scenarios

Modeling Quantum Optical Components, Pulses and Fiber Channels Using OMNeT++

Quantum Key Distribution (QKD) is an innovative technology which exploits the laws of quantum mechanics to generate and distribute unconditionally secure cryptographic keys. While QKD offers the promise of unconditionally secure key distribution, real world systems are built from non-ideal components which necessitates the need to model and understand the impact these non-idealities have on system performance and security. OMNeT++ has been used as a basis to develop a simulation framework to support this endeavor. This framework, referred to as "qkdX" extends OMNeT++'s module and message abstractions to efficiently model optical components, optical pulses, operating protocols and processes. This paper presents the design of this framework including how OMNeT++'s abstractions have been utilized to model quantum optical components, optical pulses, fiber and free space channels. Furthermore, from our toolbox of created components, we present various notional and real QKD systems, which have been studied and analyzed.Comment: Published in: A. F\"orster, C. Minkenberg, G. R. Herrera, M. Kirsche (Eds.), Proc. of the 2nd OMNeT++ Community Summit, IBM Research - Zurich, Switzerland, September 3-4, 201

Study of application of space telescope science operations software for SIRTF use

The design and development of the Space Telescope Science Operations Ground System (ST SOGS) was evaluated to compile a history of lessons learned that would benefit NASA's Space Infrared Telescope Facility (SIRTF). Forty-nine specific recommendations resulted and were categorized as follows: (1) requirements: a discussion of the content, timeliness and proper allocation of the system and segment requirements and the resulting impact on SOGS development; (2) science instruments: a consideration of the impact of the Science Instrument design and data streams on SOGS software; and (3) contract phasing: an analysis of the impact of beginning the various ST program segments at different times. Approximately half of the software design and source code might be useable for SIRTF. Transportability of this software requires, at minimum, a compatible DEC VAX-based architecture and VMS operating system, system support software similar to that developed for SOGS, and continued evolution of the SIRTF operations concept and requirements such that they remain compatible with ST SOGS operation

Specifying Reusable Components

Reusable software components need expressive specifications. This paper outlines a rigorous foundation to model-based contracts, a method to equip classes with strong contracts that support accurate design, implementation, and formal verification of reusable components. Model-based contracts conservatively extend the classic Design by Contract with a notion of model, which underpins the precise definitions of such concepts as abstract equivalence and specification completeness. Experiments applying model-based contracts to libraries of data structures suggest that the method enables accurate specification of practical software