This is a couple of things. First, NOAA and a small community built a command line-invoked crawler that a user/client can use to harvest metadata from THREDDS servers into ISO-compliant formatting (standard number: 19115). This tool is usually just refered to as "ncISO." In addition, the thinking behind this tool has also been packaged into an extension to THREDDS, called "threadsISO." Note that discussions are underway to make this functionality a default part of THREDDS, although this is still under development.
Purpose: To convert THREDDS, netCDF, or NCML-based metadata content into ISO-compliant forms. The benefit of this is that many other types of software, notably web-based catalogs (which provide OGC Catalog Services for the Web (CSW)), can then facilitate discovery and access to actual data content in these stores.
ncISO Home Page (includes threadsISO)