All applicable fields for a given service should be completed. Some information may not be available or cannot be recovered, and some fields do not necessarily apply to every service. When the information cannot be obtained or would not make sense, the field should be omitted.

Some fields are required, meaning that the fields must be present in the SERF in order for the SERF to load into SERF database. These fields are Entry ID, Entry Title, Science and Service Keywords, Service Provider, and Summary.

Other fields are deemed critical, meaning these fields are crucially important for data service selection (i.e., searching), user understanding of the data, or data access. Fields critical for user understanding of the data are Entry Title and Summary. Without these fields, users cannot know if a service is appropriate for their needs. Lastly, the Service Provider field is critical for users to be able to access the service once they decide the service is appropriate for their needs.

2. How should the service be aggregated?

A key question when writing a SERF is: What should be described in a single entry? In some cases, a group of services should be described by a single SERF. In other cases, related services may be grouped together even though they may be identifiable in smaller subsets, as in a catalog or inventory. Both situations indicate the SERF describes an aggregation of services. Your determination of the appropriate group of data to describe should be the primary guideline.

Suggestions:

• Service characteristics that might suggest separate directory entries may be:
• a unique sensor/platform/project combination
• a unique parameter, parameter combination, or set of independent variables contained in the service
• a unique processing level.
• Service characteristics that do not indicate a need for separate entries include:
• identical services available on different media
• services held at multiple locations, except when significant differences exist between the data archived in different places (i.e., different processing algorithms)
• services used for the interpretation or organization of a data set (i.e., map overlays, indices to data), which would not be listed separately but which would be mentioned in the summary.

Some rules of thumb:
1. If the SERF entries each contain virtually identical information in most fields, the SERFs should probably be aggregated by writing a single entry (or a small handful of entries). In this way, the user, when conducting a search, won't be overwhelmed by too many essentially identical entries.
2. If the data are located at one location (at a single service provider, on a single online server, etc.), a single SERF entry may be written to insure access to that service.

3. What constitutes a good title?

A good title is important because the user, when receiving the results of a metadata search, is often presented with a long list of similar titles. Titles should convey the content of the service(s) and should be descriptive enough so the user, at search time, can distinguish the content from other similar services. Generally, a good title may include parameters measured, source name, sensor name, project, or service provider center name.

Valid keywords (or valids) are important in allowing precise searching of metadata records. The use of valid keywords insures that SERFs are keyed in a consistent manner. Thus, users searching for entries will be able to retrieve all entries related to a particular criteria. In theory, a search on the term, aerosols, will return all entries about aerosol data. Therefore, it is very important for SERF authors to key SERFs with all appropriate valids in all applicable fields. SERF authors must be extremely familiar with the lists of valid keywords and understand the variety of words in the lists.

Furthermore, valid keywords are especially important to international users who may be unfamiliar with some English scientific terms. A browsable list of keywords will prompt the non-English speaker to select the most appropriate words when conducting a search.

The following fields require the use of valid keywords to aid users in searching for information: Service Keywords, Science Keywords, Sensor Name, Source Name, Project, and Service Provider Name. In addition, the following fields require the use of valid keywords to insure proper maintenance and presentation of information: Personnel Role, URL Content Type (in Related URL), and IDN Node.

Where there is a hierarchy of valids, as with Keywords, SERF authors should key SERFs to the most specific level possible. For example, it is far better to key the SERF with Reference Services > Bibliographic > Bibliographic Databases when applicable rather than Reference Services > Bibliographic. If users conduct searches with Bibliographic Databases, they will miss the SERF keyed with only Reference Services > Bibliographic.

A good summary is descriptive. It describes the service so that users are able to decide whether the service is appropriate for their needs. For a list of possible service characteristics to include in the summary, see the Summary Checklist in the Summary section of the SERFGuide.