Datasets

David Adams

ATLAS

Datasets

David Adams

BNL

December 19, 2002

PPDG meeting

Interactive analysis

December 19 , 2002Datasets PPDG Interactive analysis 2

David Adams

ATLAS

ContentsDIAL

Dataset properties

Dataset representations

Dataset package status

Future


David Adams

ATLAS

DIALDIAL is

• Distributed Interactive Analysis of Large datasets

DIAL described at• http://www.usatlas.bnl.gov/~dladams/dial/talks/021219_dial.ppt

Use DIAL to deduce dataset properties


David Adams

ATLAS

Dataset propertiesDataset is a collection of data objects

• Means to iterate over objects• Typically objects are also indexed with labels

– Unique within dataset

– For event data: event ID + type + string key> E.g. run 123, event 456, EM jet, cone_0.5

– Allows for random access

• Data may be in a persistent store– Each object has a GUID


David Adams

ATLAS

Dataset properties (cont)Dataset has content

• Indicates suitability for a particular analysis or other transformation

• Might be expressed in terms of object labels• For ATLAS event data:

– Event ID’s + type-keys for each (ATLAS) event

• (Part of type in GriPhyN VDG)


David Adams

ATLAS

Dataset properties (cont)Data in dataset has a location

• Persistent store where data may be found• List of files holding the data

– File ID’s or LFN’s> Persistent store locates physical replicas

• Or rows in RDB tables…• May be multiple locations for a dataset

– Due to different representations

– More later


David Adams

ATLAS

Dataset properties (cont)Dataset has a history

• Transformation used to create the dataset– Executable, version, input parameters

– (VDG transformation)

• Input datasets– (VDG derivation)

• Run-time properties (node, time, …)– Multiple values for distributed processing

– (VDG invocation)


David Adams

ATLAS

Dataset properties (cont)Dataset has a unique identity (name)

• So it can b referenced

Dataset has portable representation• Possible to carry around a description the

content and location of a dataset without reference to any DB’s

• Dataset package uses XML


David Adams

ATLAS

Dataset representationsThere are different ways to represent the data in a dataset

Simple datasets:• All data in a single file• Table in a RDB• Indexed list of GUID’s for a persistent store

– Commercial ODB such as Objectivity

– HES such as LCG POOL


David Adams

ATLAS

Dataset representations (cont)Compound datasets

• Concatenation of datasets– Concatenation of content

– Any overlap between content of constituent datasets must index identical objects

• Subset of a dataset– Based on content

• Result of an algorithm applied on a dataset– Virtual data


David Adams

ATLAS

Dataset package statusDatasets

• Generic implementation in place– http://www.usatlas.bnl.gov/~dladams/dataset

• Assumes content is event data• Supported representations:

– Single file> AthenaRoot format> ATLAS Monte Carlo generator output

– Concatenation of events– Selection based on event ID


David Adams

ATLAS

FutureSupport other types of ATLAS event data

Add concatenation and selection based on event content

Add representation for POOL EventCollection

Add non-event data• Relevant conditions data objects• Derived metadata• Provenance and production history

Datasets

Documents

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