Requirements

This section presents the requirements that must be met for an intermediary representation for any of the DODS supported APIs. Currently, two APIs are supported by DODS: netCDF and JGOFS. As additional APIs are incorporated into the system (e.g., HDF), the DAP may add support for the data types those handle.

1. The DODS data access protocol(DAP) can be used to map data stored using one API to calls in a second API so long as both APIs are supported by DODS.

2. It must be possible to add new data types and operators to the DAP without changing the external interface it presents.

3. The DAP does not characterize the data set based on its native implementation. The DAP supports access to data sets that consist of a single file, several files, a relational database, a set of relational databases, or any other reasonable representation.

4. The DAP makes all data sets appear cohesive--they always appear as a single store of data regardless of their actual implementation. Not yet satisfied (23 August 1996).

5. The DAP supports data sets which consist of one or more variables.

6. When a data set contains two or more variables, the DAP makes their relationship explicit. The relations are precisely described using a syntax which other computer systems can analyze.

7. The DAP describes each variable in a data set by its:
   1. Name
   2. Type
   3. Shape
   4. Units. Not yet satisfied (23 August 1996)
   5. Type-dependent characteristics
   6. ...zero or more attribute-value pairs

8. The characteristics of the different variable types are given by the data model.

9. The DAP can perform the following operations on a data set:
   1. Get data set structure description
   2. Get data set attribute list
   3. Send arguments to a data set
   4. Get values from the data set