Information Technology Reference
In-Depth Information
many credentials that are used by the gateway to access resource(s) on the user
s
behalf. A resource can deliver computing, storage, or both. Each data item has at
least one replica on a data resource and has metadata attached to it. Metadata is
represented by a key
'
value pair. Users have also access to applications consisting
of validated and ready-to-use workflows that wrap some legacy code for data
analysis. Applications have inputs and generate outputs; they also have af
-
nities
with particular data types and formats. The outputs of applications are also stored as
data entities. When a user processes data with a speci
c application, the information
about this activity is captured by the eCAT as a processing entity. Each processing
includes one or more workflow submissions, depending on the cardinality of input
data. A workflow is executed on a computing resource. The provenance informa-
tion about the data consumed and produced during a processing, the parameters,
and the history of submission status, are also stored in the eCAT database as
metadata, relationships, and attributes of these entities.
The eCAT is connected to the XNAT through a speci
c plugin using the XNAT
API. Additional plugins can be developed to extend the functionality of eCAT for
other information management systems as well. Note that eCAT is not meant to
duplicate metadata that is already stored on the XNAT; instead, it only stores
pointers to the information. The only exceptions are: (a) metadata that are speci
c
to user activities on the gateway, which are not possible, nor of direct interest of
research communities, to store in XNAT; and (b) the information that is cached in
the eCAT database and synchronized periodically. The eCAT uses the user
'
s cre-
dential tokens to authenticate with the XNAT.
10.2.2.2 Data Transport (DT)
The DT component transports data between data resources on DCIs. This service
contacts the eCAT to retrieve information needed to access the data resources, such
as hostname, type of resource and credentials. From this information it determines
how to authenticate with the data resources using the user or community creden-
tials. It autonomously performs the data transfer using third-party mechanisms as
much as possible to avoid bottlenecks. Similarly to the eCAT, DT also has plugins
that implement the necessary functionalities to enable data transfer between
resources. Two plugins are used by the AMC-NSG: for the XNAT data server
(HTTP), and for the gLite grid middleware (LFC).
10.2.2.3 Processing Manager Service (PM)
The PM component takes care of preparation, submission, and monitoring of data
processing applications that are executed on a given set of input
files. Each
application is de
ned as a gUSE concrete workflow that is exported to the gUSE
application repository. In the application de
nition, all of the steps and the sequence
of their execution are con
gured, except for the inputs and output ports that
Search WWH ::
Custom Search