CSTI Earth-to-orbit propulsion research and technology program overview

NASA supports a vigorous Earth-to-orbit (ETO) research and technology program as part of its Civil Space Technology Initiative. The purpose of this program is to provide an up-to-date technology base to support future space transportation needs for a new generation of lower cost, operationally efficient, long-lived and highly reliable ETO propulsion systems by enhancing the knowledge, understanding and design methodology applicable to advanced oxygen/hydrogen and oxygen/hydrocarbon ETO propulsion systems. Program areas of interest include analytical models, advanced component technology, instrumentation, and validation/verification testing. Organizationally, the program is divided between technology acquisition and technology verification as follows: (1) technology acquisition; and (2) technology verification

Incremental Lifecycle Validation Of Knowledge-based Systems Through Commonkads

This dissertation introduces a novel validation method for knowledge-based systems (KBS). Validation is an essential phase in the development lifecycle of knowledge-based systems. Validation ensures that the system is valid, reliable and that it reflects the knowledge of the expert and meets the specifications. Although many validation methods have been introduced for knowledge-based systems, there is still a need for an incremental validation method based on a lifecycle model. Lifecycle models provide a general framework for the developer and a mapping technique from the system into the validation process. They support reusability, modularity and offer guidelines for knowledge engineers to achieve high quality systems. CommonKADS is a set of models that helps to represent and analyze knowledge-based systems. It offers a de facto standard for building knowledge-based systems. Additionally, CommonKADS is a knowledge representation-independent model. It has powerful models that can represent many domains. Defining an incremental validation method based on a conceptual lifecycle model (such as CommonKADS) has a number of advantages such as reducing time and effort, ease of implementation when having a template to follow, well-structured design, and better tracking of errors when they occur. Moreover, the validation method introduced in this dissertation is based on case testing and selecting an appropriate set of test cases to validate the system. The validation method defined makes use of results of prior test cases in an incremental validation procedure. This facilitates defining a minimal set of test cases that provides complete and effective system coverage. CommonKADS doesn’t define validation, verification or testing in any of its models. This research seeks to establish a direct relation between validation and lifecycle models, and introduces a validation method for KBS embedded into CommonKAD

MODEL-BASED VALIDATION AND VERIFICATION OF ANOMALIES IN LEGISLATION

An anomaly in legislation is absence of completeness, consistency and other desirable properties, caused by different semantic, syntactic or pragmatic reasons. In general, the detection of anomalies in legislation comprises validation and verification. The basic idea of research, as presented in this paper, is modelling legislation by capturing domain knowledge of legislation and specifying it in a generic way by using commonly agreed and understandable modelling concepts of the Unified Modelling Language (UML). Models of legislation enable to understand the system better, support the detection of anomalies and help to improve the quality of legislation by validation and verification. By implementing model-based approach, the object of validation and verification moves from legislation to its model. The business domain of legislation has two distinct aspects: a structural or static aspect (functionality, business data etc.), and a behavioural or dynamic part (states, transitions, activities, sequences etc.). Because anomalism can occur on two different levels, on the level of a model, or on the level of legislation itself, a framework for validation and verification of legal regulation and its model is discussed. The presented framework includes some significant types of semantic and syntactic anomalies. Some ideas for assessment of pragmatic anomalies of models were found in the field of software quality metrics. Thus pragmatic features and attributes can be determined that could be relevant for evaluation purposes of models. Based on analogue standards for the evaluation of software, a qualitative and quantitative scale can be applied to determine the value of some feature for a specific model

Structure preserving specification languages for knowledge-based systems

Much of the work on validation and verification of knowledge based systems (KBSs) has been done in terms of implementation languages (mostly rule-based languages). Recent papers have argued that it is advantageous to do validation and verification in terms of a more abstract and formal specification of the system. However, constructing such formal specifications is a difficult task. This paper proposes the use of formal specification languages for KBS-development that are closely based on the structure of informal knowledge-models. The use of such formal languages has as advantages that (i) we can give strong support for the construction of a formal specification, namely on the basis of the informal description of the system; and (ii) we can use the structural correspondence to verify that the formal specification does indeed capture the informally stated requirements

On validation of multibody musculoskeletal models

We review the opportunities to validate multibody musculoskeletal models in view of the current transition of musculoskeletal modelling from a research topic to a practical simulation tool in product design, healthcare and other important applications. This transition creates a new need for justification that the models are adequate representations of the systems they simulate. The need for a consistent terminology and established standards is identified and knowledge from fields with a more progressed state-of-the-art in verification and validation is introduced. A number of practical steps for improvement of the validation of multibody musculoskeletal models are pointed out and directions for future research in the field are proposed. It is hoped that a more structured approach to model validation can help to improve the credibility of musculoskeletal models. </jats:p

Development Approaches Coupled with Verification and Validation Methodologies for Agent-Based Mission-Level Analytical Combat Simulations

This research investigated the applicability of agent-based combat simulations to real-world combat operations. An agent-based simulation of the Allied offensive search for German U-Boats in the Bay of Biscay during World War II was constructed, extending the state-of-the-art in agent-based combat simulations, bridging the gap between the current level of agent-like combat simulations and the concept of agent-based simulations found in the broader literature. The proposed simulation advances agent-based combat simulations to “validateable” mission-level military operations. Simulation validation is a complex task with numerous, diverse techniques available and levels of validation differing significantly among simulations and applications. This research presents a verification and validation taxonomy based on face validity, empirical validity, and theoretical validity, extending the verification and validation knowledge-base to include techniques specific to agent-based models. The verification and validation techniques are demonstrated in a Bay of Biscay case study. Validating combat operations pose particular problems due to the infrequency of real-world occurrences to serve as simulation validation cases; often just a single validation comparison can be made. This means comparisons to the underlying stochastic process are not possible without significant loss of statistical confidence. This research also presents a statistical validation methodology based on re-sampling historical outcomes, which when coupled with the traditional nonparametric sign test, allows comparison between a simulation and historic operation providing an improved validation indicator beyond the single pass or fail test

The Validation of Computer-based Models in Engineering: Some Lessons from Computing Science

Questions of the quality of computer-based models and the formal processes of model testing, involving internal verification and external validation, are usually given only passing attention in engineering reports and in technical publications. However, such models frequently provide a basis for analysis methods, design calculations or real-time decision-making in complex engineering systems. This paper reviews techniques used for external validation of computer-based models and contrasts the somewhat casual approach which is usually adopted in this field with the more formal approaches to software testing and documentation recommended for large software projects. Both activities require intimate knowledge of the intended application, a systematic approach and considerable expertise and ingenuity in the design of tests. It is concluded that engineering degree courses dealing with modelling techniques and computer simulation should put more emphasis on model limitations, testing and validation

An ontological view in telemedicine.

The verification and validation of information system models impact on the adequacy and appropriateness of using the value of telemedicine services for continuously optimizing healthcare outcomes. We have defined a methodology to help the modeling and rigorous analysis of the requirements of information systems in telemedicine. On one hand, this methodology will be based on a formal representation of requirements (systemic, generic domain, etc.) within a knowledge base that will be a requirements repository. On the other hand, this methodology will use conceptual graphs for the formalization of ontology of activities and the production of arguments related to the formal verification of models built from this ontology. We describe an example illustrating the engagement of conceptual graph procedures to model the contextual situations in the telemedicine development. We also discuss the way in which ethical issues will actually take place in telemedicine applications