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.
