Remote Access Update - Unidata

computerharpyΛογισμικό & κατασκευή λογ/κού

2 Δεκ 2013 (πριν από 3 χρόνια και 7 μήνες)

75 εμφανίσεις


Remote Data Access
Update

Dr. Dennis Heimbigner

Unidata netCDF Workshop

July 26, 2011

Goals


Exploit new dispatch architecture to support a
number of new remote access protocols and
associated data models


DAP 2


fully supported now


CDM Remote


in testing


netCDF
-
RPC


under development


DAP4


planning stage


Others as they gain traction

General issues


Serialization/De
-
serialization


Convert data (and meta
-
data) on the server to
some linear form suitable for transmission across
the internet


E.g DAP 2 has DDS and DAS for meta
-
data and
uses XDR for raw data


Underlying client
-
server protocol


All current and planned will use HTTP protocol


=> something like libcurl on client side and a
servlet engine (e.g. tomcat) as the server.

CDM Remote


Protocol developed at Unidata by John Caron


Goal is to transmit complete CDM data and model


CDM is netCDF
-
4
-
like model used in Thredds Data
Server


C
-
client converts CDM to netCDF
-
4 only


Rationale: DAP2 is not powerful enough to
transport complete CDM model


(De
-
)Serialization provided by Google protobuf
system.


Underlying transport is HTTP


Status: working, but needs much more testing for
edge cases

netCDF
-
RPC


Protocol developed at Unidata by Dennis
Heimbigner


Rationales:

1.
Provide a very light
-
weight client for use on limited
devices (e.g. field sensors, cell
-
phones, etc.)

2.
Allow netCDF
-
Java read/write access to HDF
-
5 via
netCDF
-
4 (also keep up with changes in HDF
-
5)


(De
-
)Serialization provided by Google protobuf
system.


Underlying transport is HTTP (for initial tests)


Status: under active development

DAP4


Proposed new version of OPeNDAP DAP2
protocol


Essentially equivalent to netCDF
-
4 model


Add new atomic types


Add groups and shared dimensions


Use sequences in place of vlen


Use modified version of DAP2 serialization


Use HTTP as underlying transport protocol


Status: planning state => on hold

Questions?