As CERA-2 has a very flexible table structure,
it is mappable to many content standards.
However, CERA-2 is mainly a database model, not a content standard.
So, a "mapping" means just to proof that a certain content
standard can be held in the CERA-2 tables.
If you want to make a content standard from CERA-2, just define a set of
required fields. To be compatible to a minimum DIF, the required fields are:
| minimum DIF | required in CERA-2 (notation: Table.attribute) |
|---|---|
| Entry_Identifier | literal identifier: Entry.entry_acronym numeric identifier: Entry.entry_id |
| Entry_Title | Entry.entry_title |
| Summary | Summary.summary |
| Parameters: Category, Topic, Term |
Topic.topic_name: Topic.topic_level=2, Topic.topic_level=3, Topic.topic_level=4 |
| Data Center: Data_Center_Name, Personnel etc. |
Block Contact, contact_type="distributor": The Entry is linked to an person/institute pair |
| Document Author: Personnel |
Block Contact, contact types="investigator", "Technical Contact", or "metadata author": The Entry is linked to a person/institute pair |
see The Global Change Master Directory (GCMD)
Unlike some content standards, CERA-2 has no fixed lists of valid keywords, as they differ from research field to research field. Instead, the use of some of the lists given at GCMD/DIF or FGDC/CSDGM is recommended to speak a common language. To make sure, that misunderstandings have no chance, CERA-2 often offers a description field in addition to the name of an entity. Furthermore, the use of the acronym field is recommended if you want to offer pull down menues to the user.
Here is an example for mapping to DIF:
The example dif was taken from:
NASA Homepage The Global Change Master Directory, a directory of Earth science data
(http://gcmd.nasa.gov/User/difguide/sample_dif.html)
on 28 July 2003.
Entry_ID: Entry.entry_id or Entry.entry_acronym
Entry_Title: Entry.entry_title
Group Personnel: corresponds to CERA-2 Block Contact
Role: Contact_type.contact_type
First_Name: Person.first_name
Discipline: corresponds to CERA-2 table Topic level 1
Group Parameters: corresponds to CERA-2 table Topic
Category: corresponds to CERA-2 table Topic level 2
Topic: corresponds to CERA-2 table Topic level 3
Term: corresponds to CERA-2 table Topic level 4
Variable: corresponds to CERA-2 table Topic level 5
Detailed_Variable: corresponds to CERA-2 table Topic level 6
End_Group
Group Temporal_Coverage: corresponds to Temporal_Coverage in CERA-2 Block Coverage
Data_Set_Progress: corresponds to CERA-2 table Progress
Group Spatial_Coverage: corresponds to Spatial_Coverage in CERA-2 Block Coverage
Location: corresponds to CERA-2 table Location
Group Data_Resolution: can be entered into CERA-2 table Quality
For a detailed description of the axes, the CERA-2 Module Data_Organization should be used.
Project: corresponds to CERA-2 table Project
Group Quality: corresponds to CERA-2 table Quality
Group Use_Constraints: CERA-2 Block Distribution, table Use_Constraint
Originating_Center: corresponds to CERA-2 Block Contact, contact_type=originator
Group Data_Center: corresponds to CERA-2 Block Contact, contact_type=distributor
Data_Center_Name: Institute.institute_name
Data_Center_URL: Institute.institute_url
Data_Set_ID: see below
Group Personnel: corresponds to CERA-2 Block Contact
Role: corresponds to CERA-2 table Contact_type
First_Name: Person.first_name
...
End_Group
End_Group
Group Distribution: corresponds to CERA-2 Block Distribution
Distribution_Media: CERA-2 table Access_Type
Distribution_Format: CERA-2 table Format
Fees: CERA-2 table Fees
End_Group
Group Reference corresponds to CERA-2 Block Reference
Group Summary corresponds to CERA-2 table Summary
IDN_Node: ...who really needs this, can use CERA-2 table Entry_Type
Last_DIF_Revision_Date: Entry.review_date
DIF Data_Set_ID: If the data set ID at the site of the data distribution centre is meant as a
stable reference to get the publicated data, this reference should be filled in into
CERA-2 Block Reference, the ID into Citation.access_spec.
If it is not meant as a stable reference, it is unadvisable to handle inofficial IDs of
other institutes. In this case the ID might be stated in Summary.summary - Entry.creation_date
then is a date when this ID was valid.
For comments and suggestions contact Frank Toussaint
last changes: 2003-07-31