Software Reuse Within the Earth Science Community

The reuse of software assets can be critical to the development of large-scale software projects where budget and reliability are paramount. Yet many of the benefits of software reuse are either not recognized or overlooked. The majority of software assets are not made available to peers or a wider community. Therefore, a key activity in promoting software reuse is the initiative to increase the awareness of reuse enablement systems. An ideal Earth science reuse enablement system should ensure that reusable software assets are readily available to the software developers who want to use them to build new or enhance existing Earth science applications. This can be done by placing the assets into a software catalog or repository system. Many such systems exist, mostly outside of the Earth science domain, each designed for a particular purpose. Some are domain- specific, covering one particular subject area, while others are more general, covering a large variety of fields. Each is well- designed for its target audience. Many candidate systems that exist provide open-source software solutions. However, user goals, quality control, and overall usability determine the usefulness of a system to the community of Earth science software developers. The software used to create these systems also varies, ranging from standard HTML to full repository software packages like Repository in a Box (RIB), which uses the Basic Interoperability Data Model (BIDM), IEEE Standard 1420.1. The NASA Earth Science Data System (ESDS) Software Reuse Working Group has examined a variety of these systems, and focused on their applicability to the Earth science domain. Within a set of requirements designed for the Earth science community, this paper compares selected features of these systems, such as providing reviews for assets or the software used to design the site, and how the presence or absence of these features affects the system's ability to promote reuse.

NASA's Earth science program—increasing science opportunity and payoff through small satellites

It has been 18 months since NASA conducted the highly successful Cirrus Regional Study of Tropical Anvils and Cirrus Layers‐Florida Area Cirrus Experiment Study (CRYSTAL‐FACE). The measurement campaign was designed to investigate the physical properties and formation processes of tropical cirrus clouds. CRYSTAL‐FACE was sponsored by NASA's Earth Science Enterprise as an integral component of its Earth observation research strategy and included substantial collaboration with the National Oceanic and Atmospheric Administration, the National Science Foundation, the Department of Energy and the Naval Research Laboratory. During July 2002, the mission's six aircraft (NASA ER‐2, NASA WB‐57, Scaled Composites Proteus, University of North Dakota Citation, NSF‐supported NRL P‐3,and NRL Twin Otter) operated from the Key West Naval Air Facility.

The time horizon of global change is on scales of years, decades, centuries, and beyond, and this variability can have a tremendous regional impact. The importance of the oceans and cryosphere in climate change increases with time scale because of their large thermal inertia. NASA's Earth Science Enterprise has developed a research strategy to address climate relevant questions about the ocean and cryosphere, such as: how is the global ocean circulation varying on interannual, decadal, and longer time scales?; and what changes are occurring in the mass of the Earth's ice cover? This strategy starts with basic exploration utilizing satellite measurements, leads to improved understanding by incorporating data and models, and ends with improved prediction and benefit for the future. In this paper we consider the science and technology challenges for the ocean and cryosphere strategy over the next twenty-five years.

The Stratospheric Aerosol and Gas Experiment (SAGE) III is the fourth generation of solar occultation satellite instruments designed by NASA to measure vertical profiles of aerosol extinction and the molecular densities of gaseous species in the atmosphere. With an expanded spectral range compared with its predecessors, SAGE III has the capability to retrieve profiles of atmospheric temperature and pressure utilizing multi-spectral measurements of the oxygen A-band absorption feature near 762 nm. As part of NASA's Earth Science Enterprise, Earth Observing System, the first of two SAGE III instruments was successfully launched onboard the Meteor-3M satellite in December 2001. Given the inherent insensitivity of solar occultation experiments to long-term instrument degradation and the expected lifetime of the instruments (6+ years), the SAGE III instruments should provide a long-term record of self-calibrated, high vertical resolution temperature and pressure measurements. These measurements will be valuable for monitoring temperature trends in the stratosphere and mesosphere and for comparison studies with other temperature data sets.

The authors demonstrate the current capabilities of NASA's finite-volume General Circulation Model in high-resolution global weather prediction and discuss its development path in the foreseeable future. This model is a prototype of a future NASA Earth-modeling system intended to unify development activities across various disciplines within NASA's Earth Science Enterprise.

Educational outreach activities for Landsat-7

The Students' Clouds Observations OnLine or S'COOL project was piloted in 1997. It was created with the idea of using students to serve as one component of the validation for the Clouds and the Earth's Radiant Energy System (CERES) instrument which was launched with the Tropical Rainfall Measuring Mission (TRMM) in November, 1997. As part of NASA's Earth Science Enterprise CERES is interested in the role clouds play in regulating the climate. Over thirty schools became involved in the initial thrust of the project. The CERES instrument detects the location of clouds and identifies their physical properties. S'COOL students coordinate their ground truth observations with the exact overpass of the satellite at their location. Their findings regarding cloud type, height, fraction and opacity as well as surface conditions are then reported to the NASA Langley Distributed Active Archive Center (DAAC). The data is then accessible to both the CERES team for validation and for educational application via the Internet. By March of 1998 ninety-three schools, in nine countries had enrolled in the S'COOL project. Joining the United States participants were from schools in Australia, Canada, France, Germany, Norway, Spain, Sweden, and Switzerland. The project is gradually becoming the global project envisioned by the project's creators. As students obtain the requested data useful for the scientists, it was hoped that students with guidance from their instructors would have opportunity and motivation to learn more about clouds and atmospheric science as well.

Component-based software development (CBSD) is the process of assembling existing software components in an application such that they interact to satisfy a predefined functionality. This approach can potentially be used to reduce software development costs, assemble systems rapidly, and reduce the maintenance overhead. One of the key challenges faced by software developers is to make component-based development (CBD) an efficient and effective approach. Since components are to be reused across various products and product-families, components must be characterized and tested properly. The present paper is a survey paper and firstly, it discusses CBD and related issues that help improving software reuse. Testing of third party components is a very difficult task in the absence a properly characterized software component. Besides improving software reusability, component characterization also provides better understanding of architecture, better retrieval, better usage and better cataloguing. This paper mainly discusses the essence of proper component characterization that ultimately helps the developers in software reuse, which is highly desirable in component-based software development. Further, paper also discusses other benefits of component characterization that are most essential in component-based development.

As the demand for more flexible, adaptable, extensible, and robust Web based enterprise application systems accelerates, adopting new software engineering methodologies and development strategies becomes critical. These strategies must support the construction of enterprise software systems that assemble highly flexible software components written at different times by various developers. Traditional software development strategies and engineering methodologies, which require development of software systems from scratch, fall short in this regard. Component based software engineering offers an attractive alternative for building Web based enterprise application systems. CBSE works by developing and evolving software from selected reusable software components, then assembling them within appropriate software architectures. By promoting the use of software components that commercial vendors or in-house developers build, the component based software development approach promises large scale software reuse.

Simultaneously achieving efficiency and flexibility in enterprise software production has been a considerable challenge for firms. Newer software development paradigms such as component-based and model-driven development attempt to overcome this challenge by emphasizing modular design of complex systems. However, there is a paucity of rigorous empirical research on the use of such software methodologies and the associated extent to which trade-offs between efficiency and flexibility can be influenced. Addressing this gap, we investigate the performance outcomes of a model-driven, component-based software development methodology using data collected from an enterprise software development firm that deployed such a methodology for its product development processes. Examining the design, development, and implementation of 92 business software components of the firm's enterprise resource planning product, we discuss how the design of software components, specifically component granularity, affects development efficiency (development effort and defects) and flexibility (customization effort). Our results suggest that (a) components that are coarse grained are associated with higher flexibility (lower customization effort) but are also associated with lower development efficiency (more development effort and defects), and (b) defect proneness of a component plays a mediating role on the relationship between component granularity and flexibility. These findings present strong evidence for the existence of trade-offs between efficiency and flexibility in mass-customized software product life cycles. They establish component granularity as a key design dimension that needs to be managed judiciously to enable potential trade-off shifting mechanisms through the use of software methodologies that emphasize modular design approaches.

During recent years, neural network research has been extended to a large number of different fields, increasingly attracting the interest of workers from various disciplines. The computer simulations carried out with this research require an appropriate software environment. The computational similarities of many kinds of simulations allow the design of software components that are largely independent of the specific application. These considerations are reflected, for example, by the general layout of the MENS network simulator, as described in the accompanying first paper. This paper presents the design considerations for the simulator's different software components in more detail. In particular, design and implementation are discussed with respect to computational and memory efficiency. The discussion includes, for example, the representation of a network by the simulator's data structure, the file-driven configuration and initialization of a network, the simulator's stimulus and monitor system, and the simulator's control structures. In addition, the separation and interaction of application-specific and application-independent software components are addressed. Particular performance aspects comprise the implementation of synaptic delays, the dynamic deletion of synaptic links in network learning, and the preprocessing of stimulus films. In addition, some general aspects of simulator performance and testing are considered. The material presented in this paper concerns both the development of new simulation software and the efficient use of existing programs. Therefore, both the general user as well as the software designer may hopefully benefit from this presentation.

Software reuse has been regarded as one of the most important areas for improving software development productivity and the quality of software. Research and practice has shown that software reuse can be used for developing products from reusable assets in a routine manner, on an industrial scale. However successful application of software reuse is limited to certain domains and not widespread across the software industry. There is no clear consensus between input and, output artifacts and the requirements that an effective reuse process must have. To examine the issues and concerns in more detail we have completed surveys on software reuse in the conventional software engineering (CSE) community and in the software product line (SPL) community to compare and contrast the results for similarities and differences in software reuse philosophy. This paper outlines some of the identified differences and similarities of issues and concerns in software reuse in both communities and what one community can gain from the other to overcome the identified software reuse problems. The comparison highlights areas where the existing SPL and CSE communities provide extensive support in software reuse and those in which the SPL and CSE communities are deficient, suggesting an understanding of the factors resisting software reuse in both communities.

The large scale application of reuse to support software development is not a new concept. Over twenty years ago, M. D. McIlroy expressed the need for: “… standard catalogues of routines, classified by precision, robustness, time-space performance, size limits, and binding time of parameters.” [McIlroy 68] He also provided insight that is still valid into: “… the kinds of variability necessary in software components, ways of producing useful inventories, types of components that are ripe for such standardization, and methods of instituting pilot production.”McIlroy emphasized the importance of abstraction of common principles in developing these routines, the need for automatic generators, and uniformity of engineering. He also enumerated the degree of parameterization needed for successful reusable software: Choice of precisionChoice of robustness, trading off reliability and time-space performanceChoice of time-space behaviorChoice of algorithmChoice of interfaces with standards for types of error conditionsChoice of storage accessing methodChoice of data structures within a given algorithm or within different related algorithmsIn the utility and tool area, these concerns have been met with stable, understandable and supported reusable software subsystems to support applications development. Examples of this software are collections of abstract data structures, data base management systems, development environments, and network managers. Requirements for new applications that depend on reuse of such general subsystems software are specified in light of the existence of that software. The development can achieve significant productivity gains when the software subsystems are reused.Except in reusing these subsystems, reusable software practice has not had the same level of success in specific application areas, with few exceptions. For domains such as command and control, communications, avionics, and shipboard systems, reusable software must address specific application requirements particular to the given domain. The development of a reusable air traffic control architecture by Thomson-CSF is an example of reuse that addresses the requirements of a specific application. [Andribet 90] The details of the architectures and components developed by Thomson-CSF remain within the company, and may have limited applicability for other organizations that develop similar systems but use alternate design strategies. The Common Ada Missile Packages (CAMP) project has also produced reusable software components, primarily for missile operational software, but this software has seen only limited application. [McNicholl 88]

The authors describe their research which improves software reuse by using an automated approach to semantically search for and retrieve reusable software components in large software component repositories and on the World Wide Web (WWW). Using automation and smart (semantic) techniques, their approach speeds up the search and retrieval of reusable software components, while retaining good accuracy, and therefore improves the affordability of software reuse.A program understanding of software components and natural language understanding of user queries was employed. Then the software component descriptions were compared by matching the resulting semantic representations of the user queries to the semantic representations of the software components to search for software components that best match the user queries.A proof of concept system was developed to test the authors' approach. The results of this proof of concept system were compared to human experts, and statistical analysis was performed on the collected experimental data. The results from these experiments demonstrate that this automated semantic‐based approach for software reusable component classification and retrieval is successful when compared to the labor‐intensive results from the experts, thus showing that this approach can significantly benefit software reuse classification and retrieval.