Lattice 2004Chris Maynard1 QCDml Tutorial How to mark up your configurations.

Lattice 2004 Chris Maynard 1

QCDml Tutorial

How to mark up your configurations


Contents

FAQs on using XML schema Defining QCDml

– Namespaces and validation

Example XML IDs– Ensemble and config

• Ensemble: actions, algorithms and management metadata

• Config: what goes where

Babble about BinX Metadata catalogue demo


FAQs about XML schema

What is XML schema?– Collection of rules for XML documents– An XML schema is itself an XML document

Why do we need an XML schema?– Computers can read and understand XML IDs– <length>16</length>– Meaning of length is context dependent

Do I need to learn XML schema– No. Schema makes it easier to produce XML


QCDml1.0

Metadata split into two schemata– Ensemble XML <markovChain/>– Config XML <gaugeConfiguration/>

• N.B. use lowerCamelConvention

ILDG website for XML schema files– http://www.lqcd.org/ildg– Go to Metadata and follow links– Version 1.0 online and ready to use


Namespaces

Example XML ID for UKQCD data

XML Namespace defined by W3.org as A collection of names identified by a URI

reference


First namespace

URI defines namespace for QCDml

This is the default namespace All elements of QCDml belong to this

namespace


Second namespace

Namespace of XML schema itself

Prefix <xsi:> for elements of XML schema

XML ID is valid against WC3 XML schema


SchemaLocation

The namespace of the schema

The file which contains the schema URI namespace can be URL of the

schema instance – not compulsory


Logical filename

Unique URI for a file in a namespace

Uniquely identifies this ensemble in ILDG namespace


Validation

Verify XML ID is valid against a schema– Schema aware applications can use XML ID

Can write XML in vi,emacs etc CMM uses XMLSpy for schema and ID

manipulation– built in validator, create XML ID from schema

http://www.w3.org/XML/Schema– Many different tools


QCDml Ensemble <action/>

Split into quark and gluon sections

UML representation of schema


Ensemble XML - actions

Inheritance tree - check for your action in schema


Which elements?

Schema defines required elements UKQCD NP clover


UKQCD Ensemble example

Glossary: not computer readable

How cSW was determined

References etc


NumberOfFlavours

Number of degenerate flavours for which these coupling values apply


MILC 2+1 staggered Ensemble

<couplings/> is array valued

Non-degenerate flavours shown with different couplings

Mass 0.02

Mass 0.05


Management

Metadata created when Ensemble registered with ILDG

Yet to be created middleware will do this


Algorithm

Algorithmic metadata split between ensemble and algorithm

Most metadata is unconstrained parameter <name/> <value/> pairs

Relevant information can be found– Glossary document for references etc

Hierarchical structure for algorithms is– difficult to create– difficult to make extenisble


Algorithm: Example

Glossary for detailed information

Unconstrained parameter <name/> <value/> pairs


Config XML

Machine and code details

In principle these could be different for configurations in the same ensemble


Config Management

Checksum for config binary

Zeroeth <revision/> is generate data, as this occurs before submission to ILDG


Precision

Precision (double or float) in which the calculation was done


markovStep

Logical File name of the ensemble in the ILDG namespace


dataLFN

Logical File name of the configuration in the ILDG namespace


The markov chain

Where the configuration is in the trajectory of markov chain


avePlaquette

Very useful metadata, can be used to check data transformations are correct


Config: UKQCD example

Application codes can write this info either as QCDml

Or tool can convert the IO to QCDml


BinX

XML markup for binary data Library for manipulating marked up data Production codes do not use BinX library

– But easy to mark up data format in BinX style– ILDG middleware can use BinX for data

manipulations– http://www.edikt.org/binx

BinX under discussion by Middleware + Metadata WG for file format.


Gauge config BinX

Small

Written once per ensemble

write code on top of BinX library

Change array order

2x3 3x3

average plaquette

ILDG BinX based gauge config manipulator?


Correlator data

Compact. No standard shape to correlators

BinX will read in any shape


Array stripper

BinX + BJ’s Xpath reader

Code reads this XML

Produces single slice array in text/XML

From any size/shape array

Schema for correlator channels

ILDG middleware extract channel from any correlator


Correlator dictionary

Possible QCDml extension Correlator AP code knows channel details

– IO AP write dictionary• Channel n is zero p pion

User requests pion– Stripper reads dictionary to find pion– Pulls channel n from correlator

Very easy to read other peoples data!

),,,,( 21 mnnnptCC


Metadata demonstration

UKQCD metadata catalogue– Browser is based on OGSA-DIA– Open source

• You can get it at www.forge.nesc.ac.uk

Browser reads the schema– Build XPath query graphically– Result handler

• Display XML and GET data• Render web page of results?• Create XML IDs?


ILDG metadata

ILDG proposal: – All collaborations publish metadata

Example method– UKQCD metadata catalogue access is not

authenticated– Anyone can read it

ILDG aggregation of metadata catalogues– Mark up data in QCDml– No extra effort required.

Lattice 2004Chris Maynard1 QCDml Tutorial How to mark up your configurations.

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