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What is a SERF?

SERF is the acronym for Service Entry Resource Format, a de-facto standard used to create directory entries that describe a group of data services and applications. A SERF consists of a collection of fields that detail specific information about the service. Seven fields are required in the SERF; the others expand upon and clarify the information. Some of the fields are free text or unrestricted fields, others require the use of valids.

The SERF allows users of data to find tools and services to manipulate data. The SERF contains those fields that are necessary for users to decide whether a particular service would be useful for their needs.

The Global Change Master Directory (GCMD) offers online descriptive information about environmental and Earth science data sets located throughout the world. As an additional service for the Earth sciences community, GCMD also offers descriptive information about commercial and non-commercial data services that could assist its user community in analyzing, processing, and evaluating Earth science data sets.

History of the SERF

In 1998, a proposal was submitted to the Earth Science Technology Office (ESTO) for cataloging Earth science services and for aiding researchers in finding tools that they may use with and their data products. Many data products available to researchers also have related data services, yet there was no easy way of locating these software, tools and services. This prototype would provide a system to catalog and allow users to locate Earth science services. This included providing a service metadata format, metadata authoring tools, and a web-based interface for cataloging, searching and retrieving Earth science services. The GCMD already had a similar infrastructure in place to deal with data products. The existing data description format was modified to create a Services Entry Resource Format (SERF) metadata format. The GCMD proposed a list of service categories and topic keywords that was based on a number of Earth science service-related keywords obtained from other groups. These were made available for comments and feedback to a number of potential user groups such as the EOSDIS User Services Working Group (USWG), Earth Science Information Partnership (ESIP) Federation, and the Committee on Earth Observation Satellites (CEOS) organizations. Service related catalog tools were created based on the existing data tools. This allowed the current data products system to be used as a springboard to implement a new service related system. The prototype system and a SERF document creator were made public in 2000.

Parameter Keyword Rules

The following rules have been used in determining TERMs and VARIABLEs for the GCMD Parameter Keywords. These rules are used in GCMD's procedures for modifying GCMD keywords. TOPICs, TERMs, and VARIABLEs contain VALID lists to assist the user in locating Earth science data services of interest. These VALIDs are expected to remain fairly stable over time, although suggestions for additions and/or changes will always be considered.



    1) The service advertised in the GCMD must be specific and directly related to the processing, viewing, analysis, archival, retrieval, production, interpretation, discovery, acquisition, modeling, visualizing, formatting, or indexing of Earth science data. The GCMD staff will be responsible for determining the appropriateness for inclusion and for the quality control of the entries by working with service providers. 

    2) A four level hierarchy of Services keywords will be maintained, positioned as CATEGORY/TOPIC/TERM/SERVICE SPECIFIC NAME. 

    3) All keywords at the four levels of hierarchy should be parallel and 'mutually exclusive'.The GCMD keyword authorities will determine if modifications or additions are appropriate. All modifications or additions must strictly adhere to the rules contained herein. 

    4) Services should be classified by their primary purposes. Existing service keywords at the TOPIC/TERM/SERVICE SPECIFIC NAME level will be used to associate the services that apply to the SERF.The summary can be used for further clarification. Providers may not submit more than one entry (SERF) for any one service. 

    5) Existing science keywords at the TOPIC/TERM/SERVICE SPECIFIC NAME level will be used to associate the service with a science TOPIC/TERM/SERVICE SPECIFIC NAME.


This document should be cited as:
Service Entry Resource Format (SERF) Writer's Guide, 2018.
Global Change Master Directory.
National Aeronautics and Space Administration.



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