Data Access Layer Interface

DALI is a base set of requirements and rules that all DAL services will follow. The goal is not to define what service must do, but rather to specify various common service resources or operations so t if a service specification includes a common operation it will do so by referencing the DALI specification. This will make it much easier for common service features to be defined once and implemented the same way wherever they are needed.

Discussion Topics for the Pune2011 interop

1. Standard resources: sync, async, availability, capabilities, tables

- these are in fact 5 capabilities, but in future we leave the actual names free (to be specified in the VOSI-capabilities + registry record)

TBD - value in fixing the resource names for the VOSI resources themselves and only leaving the 1+ DAL service resources free to be named?

2. Standard job parameters

REQUEST, VERSION, FORMAT, MAXREC, RUNID

3. rules for literal values

a. dates: one variant of ISO8601 only

b. ranges: does this actually belong in PQL?

c. lists: agreed to follow the HTTP spec, which says that multiple occurences of a parameter and a single occurence with comma-separated list of values is equivalent

4. Can individual params (here or in PQL) define something that conflicts with 3? e.g. UPLOAD violates 3c

5. overflow in VOTable - as specified in TAP

6. UPLOAD: table upload (re: object-list query science use case)?

a. the UPLOAD param specified here (as in TAP)

b. how to reference the uploaded table(s) specified in PQL? TAP or ADQL? (next revision)

7. error responses

a. VOTables error document

b. when are HTTP status codes (and text/plain) appropriate?