In this paper we present an overview of the Grid OCL graphical object connecting language Grid OCL is an extension of Grid introduced last year that allows users to interactively build complex data processing systems by selecting a set of desired tools and connecting them together graphically Algorithms written in this way can now also be run outside the graphical environment

Schutz, B.

Taylor, I.

MPG.PuRe

Grid OCL   A Graphical Object Connecting LanguageI  J  Taylor Department of Physics and Astronomy  University of Wales  College ofCardi  PO BOX   Cardi  Wales  UK  EmailIanTaylorastrocfacukB  F  SchutzAlbert Einstein Institute  Max Planck Institute for GravitationalPhysics  Schlaatzweg   Potsdam  Germany EmailschutzaeipotsdammpgdeAbstract  In this paper we present an overview of the Grid OCLgraphical object connecting language  Grid OCL is an extension of Gridintroduced last year that allows users to interactively build complex dataprocessing systems by selecting a set of desired tools and connecting themtogether graphically  Algorithms written in this way can now also be runoutside the graphical environment   IntroductionSignalprocessing systems are becoming an essential tool within the scienticcommunity  This is primarily due to the need for constructing large complexalgorithms which would take many hours of work to code using conventionalprogramming languages  Grid OCL Object Connecting Language is a graphical interactive multithreaded environment allowing users to construct complexalgorithms by creating an objectoriented block diagram of the analysis required   An OverviewWhen Grid OCL is run three windows are displayed  A ToolBox window aMainGrid window and a Dustbin window to discard unwanted units  Figure  showsthe ToolBox window which is divided into two sections  The top section showsthe available toolboxes found by scanning the toolbox paths specied in theSetup menu and the bottom shows the selected toolboxs contents  Toolboxesand associated tools can be stored on a local server or distributed throughoutseveral network servers  Simply adding the local or http address in the toolboxand tool path setup allows onthey access to other peoples tools  A post doctoral programmer at Cardi  who has been developing Grid OCL since January Professor Schutz is a Director of the Albert Einstein Institute PotsdamFigure   Grid OCLs ToolBox window  Toolboxes can be organisedin a similar way to les in a standard le manager Units are created by dragging them from the ToolBox window to the desiredposition in the MainGrid window and then connected together by dragging froman output socket on a sending unit to an input socket of the receiving unit  Thealgorithm is run by clicking on the start button see Figure 	 in a single stepfashion i e  one step at a time or continuously   New Features and ExtensionsGroups of units can now be saved along with their respective parameters  Suchgroups can also contain groups which can contain other groups and so on  Thisis a very powerful feature which allows the programmer to hide the complexityof programs and use groups as if they were simply units themselves  Manyimprovements have been made to the graphical interface including compactingthe look and style of the toolbox adding a snapto cable layout and many moreinformative windows  The major change however is that now Grid consists ofan object connecting language OCL and a separate user interface  This meansthat the units can be run from within the user interface or as a standaloneprogram Collaborators are working on tools for various signal and image problemsmultimedia teaching aids and even to construct a musical composition system Currently in our new release we have toolboxes for various signal processingprocedures animation and a number of image processingmanipulation routinestext processing tools e g  nd and replace grep and line counting recursivelythrough subdirectories mathematical and statistical units a general purposemathematical calculator see next section and a number of exible importingand exporting units 	Figure 	  A snapshot of Grid OCLs programming window   MathCalcThe MathCalc unit interprets optimises and evaluates arithmetic expressionsusing streamoriented arithmetic  It recognises a large number of functions andconstants  It can be used to evaluate scalar expressions to process input datasets or to generate output data sets  All calculations are performed in doubleprecision real arithmetic Streamoriented arithmetic can be dened as the application of an arithmetic expression to each element of a stream independently  Thus if B isthe sequence b  b	    bn then the function sinB evaluates to the sequencesinb  sinb	    sinbn  MathCalc distinguishes between constants and sequences or sets  Sets data sets are sequences of numbers and constants aresingle numbers essentially sequences of length   In a MathCalc expression thetwo can be mixed very freely with the restriction that all sequences must havethe same length  Sequences or constants can be obtained from the input nodes ofthe MathCalc unit  The example given in the MainGrid window see Figure 	demonstrates the exibility of the MathCalc unit The rst MathCalc unit creates a 	 Hz sine wave by using the equationsinsequence	   	   PI   	 where the sample rate is kHz MathCalc will optimise this to 	PI 	  sequence	  This is then transformed into a SampleSet type by adding its sampling frequency i e   kHz The second MathCalc unit adds Gaussian noise to its input i e  by typinggaussian	s  The  means node  and the s means that it is a sequence as opposed to a c which would a constant  The resultant amplitudespectrum FFTASpect is shown from Grapher see Figure  Once the signal is displayed it can be investigated further by using one ofthe Graphers various zooming facilities  Zooming can be controlled via a zoomwindow which allows specic ranges to be set or by simply using the mouse todrag throughout the image  For example by holding the control key down anddragging down the image is zoomed in vertically and by dragging across fromleft to right zoomed in horizontally  The reverse operations allow zooming out Also once zoomed in by holding the shift key and the control key down themouse can be used to move around the particular area you are interested in  WeFigure   Graphers output any grapher can simultaneously display many signals each with its own colour and line style also have another powerful zooming function which literally allows the user todrag to the position of interest and the image will zoom in accordingly   Grid OCL  Past and PresentGrid originated from an implementation of the system using C and InterViews Taylor  Schutz  but was abandoned in early   Version twoTaylor  Schutz  was written using the Java Development Kit JDK   	but this was updated in order to be compatible with the new JDK   x kit We also reimplemented the base classes and to create OCL  The most recentversion of Grid OCL in November  is a late alpha and goes by a dierentname Triana OCL  Triana OCL will be entering its beta testing stage earlynext year followed by a nal version shortly after  We are in the process of beingable to provide a commercial version of the software for which support can begiven  Nonetheless we will always provide it in a free downloadable from theWWW with a certain time limit  or  months  Our main goal is to create avery wide user base ReferencesTaylor I  J   Schutz B  F    The Grid MusicalSignal Processing SystemInternational Computer Music Conference pp   Taylor I  J   Schutz B  F    The Grid Signal Processing System  Astronomical Data analysis Software and Systems VI 	 httpwwwastrocfacukTriana

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Grid OCL: A Graphical Object Connecting Language

Abstract. In this paper, we present an overview of the Grid OCL graphical object connecting language. Grid OCL is an extension of Grid, introduced last year, that allows users to interactively build complex data processing systems by selecting a set of desired tools and connecting them together graphically. Algorithms written in this way can now also be run outside the graphical environment. 1

Grid OCL: A Graphical Object Connecting Language

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