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Data Types

Data Types. written by Gabriele Carcassi performed by Bob Dalesio based on ideas/requirements from Bob Dalesio , Kay Kasemir , Ralph Lange, James Roland, Guobao Shen, Greg White Oct 12 2010. Scope and requirements.

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Data Types

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  1. Data Types written by Gabriele Carcassi performed by Bob Dalesio based on ideas/requirements from Bob Dalesio,Kay Kasemir,Ralph Lange, James Roland,Guobao Shen, Greg White Oct 12 2010

  2. Scope and requirements • Java interfaces define client side data structures to represent data for control systems and high level applications • pvData structure define data structure that represent information passed on the wire • Compatibility between Epics 3 and 4 • Java interfates as part of PVManager for convenience; no dependencies on PVManager • nor PVManager depends on them

  3. References and documentation • Project available at http://pvmanager.sourceforge.net • JavaDocs (with actual documentation) at http://pvmanager.sourceforge.net/apidocs/index.html • Package org.epics.pvmanager.data

  4. Design guidelines • All data types defined through interfaces • Two types of interfaces • Full type (e.g. VDouble, VMultiInt, VStatistics): they represent types that are actually implemented and can be asked; they all look like VXxx (where V is value) • Partial type (e.g. Scalar<T>, Alarm, Time): they represent common parts of data across different full types; they are defined separately so that we have one definition and so that clients can code to that partial interface • Full types are made up as collections of partial types (mostly don’t define new methods)

  5. VDouble • Let’s start with the most common one, VDouble • Scalar<Double> • Alarm • Time • Display • Let’s go through details of all interfaces

  6. Scalar<T> • Defines: • T getValue() • Returns the value of some type.

  7. Alarm • Defines: • AlarmSeveritygetAlarmSeverity(); • AlarmStatusgetAlarmStatus(); • AlarmSeverity: NONE, MINOR, MAJOR, INVALID, UNDEFINED (3 bits) • AlarmStatus: DEVICE, DRIVER, RECORD, DB, CONF, UNDEFINED, CLIENT, NONE (4 bits) • Gives the highest alarm and where it originates; first pass, generic information • VExtendedAlarm is for more detailed information

  8. Time • Defines: • TimeStampgetTimeStamp(); • Integer getTimeUserTag(); • booleanisValid(); • TimeStamp is a nanosecond accuracy instant • Investigating use of JSR-310 Date and Time API • javax.time.Instant (64 bit second + 32 bit nanosecond) • TimeUserTag can be used to identify fill patterns or anything your heart desires • isValid() used to flag when the time source is “bad” (time was not set, returns always EPICS time 0, …)

  9. Display • Defines: • Double getLower/UppterDisplayLimit(); • Double getLower/UppterCtrlLimit(); • Double getLower/UppterAlarmLimit(); • Double getLower/UppterWarningLimit(); • String getUnits(); • NumberFormatgetFormat(); • Limits are always in double, regardless of the numeric type

  10. VDouble • VDouble is one type, and defines all those elements. • One can still have partial implementations, that throw UnsupportedOperationException on the pieces that they do not implement or return null. • We want to avoid 2^4 combinations

  11. All scalar types • VDouble – Scalar<Double>, Alarm, Time, Display • VInt - Scalar<Integer>, Alarm, Time, Display • Explicitly no VFloat, VShort, VByte… • Is VBoolean needed? • VString - Scalar<String>, Alarm, Time • VEnum - Scalar<String>, Enum, Alarm, Time

  12. Enumeration • Enum defines: • List<String> getLabels(); • VEnum defines: • intgetIndex(); • Should the index be byte, short or int?

  13. Scalar types

  14. Multi dimensional arrays • VDoubleArray - Array<Double>, Alarm, Time, Display • VFloatArray- Array<Float>, Alarm, Time, Display • VIntArray- Array<Integer>, Alarm, Time, Display • VShortArray- Array<Byte>, Alarm, Time, Display • VByteArray - Array<Byte>, Alarm, Time, Display • (VBooleanArray ?) • VStringArray - Array<String>, Alarm, Time • VEnumArray - Array<String>, Enum, Alarm, Time

  15. Array<T> • Defines: • List<Integer> getSizes(); • The list of sizes for the multi dimensional array. One dimensional array can simply disregard this field. Difference between primitives and objects forces the array in the Full type. • VDoubleArray: double[] getArray(); • VIntArray: int[] getArray(); • VEnumArray, VStringArray: String[] getArray(); • VEnumArray also defines int[] getIndexes(); • …

  16. Multi Channel arrays • Multiple values coming from different channels (e.g. all X BPM readbacks) • VMultiDouble: MultiScalar<VDouble>, Alarm, Time, Display<Double> • VMultiInt: MultiScalar<VInt>, Alarm, Time, Display<Integer> • VMultiString: MultiScalar<VString>, Alarm, Time • VMultiEnum: MultiScalar<VEnum>, Enum, Alarm, Time • (May need others VMultiDoubleArray, ... ?)

  17. MultiScalar<T> • Defines: • List<T> getValues(); • List<String> getNames(); • Should labels for enums be the same across all values, or can they be different? (Note: VEnumArray already may cover the case for same metadata) • Should metadata for numeric data be forced to the same? Or should each carry their own? (Note: numeric arrays may cover the case for same metadata)

  18. Multi Channel Array

  19. Statistics • VStatistics: Statistics, Alarm, Time, Display<Double> • Statistics define: • Double getAverage(); • Double getStdDev(); • Double getMin(); • Double getMax(); • Integer getNSamples(); • Does not define how it’s calculated (different weights)

  20. VTable • Defines: • intgetColumnCount(); • intgetRowCount(); • Class<?> getColumnType(int column); • String getColumnName(int column); • Object getColumnArray(int column); • A table is a list of columns. A column is an array of elements of a particular type plus a name. • Different column may have different size: rowCount is the maximum across all columns

  21. VTable

  22. VImage • Defines: • intgetHeight(); • intgetWidth(); • byte[] getData(); • VTablegetMetadata(); • How do we describe encoding? • Is VTable good enough for metadata? Is it too much? Do we need to divide metadata for each image from the metadata that does not change for each image? • Should this have Time and Alarm?

  23. VImage

  24. VExtendedAlarm • Defines: • List<Condition> getConditions(); • String getMessage(); • Condition defines: • String getName(); • AlarmSeveritygetSeverity(); • booleanisActive(); • VExtendedAlarm gives you the full list of alarms for a device. It says which ones are active. It provides an error message • Should each condition also have the AlarmStatus?

  25. Status • Many types are already operational in PVManager with Epics 3, simulated generation and aggregation • Scalar and Array types can be directly generated by JCADataSource and simulated sources • VTable used in client-side aggregation • VImage used in clieant-side computation • VMultiDouble used for synchronized array reconstruction

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