Examples of searching the Registry:

For this example I consider only catalogues, not extraction of data from images, spectra etc. If we were doing the latter we would need additional ResourceMetadata about angular coverage, resolution etc.

I have used what I hope are JAVA arithmetical and logical operators in most places for brevity, occasionally I have spelt out operators for clarity.

1. RegistryQuery for potential Brown Dwarfs located in Galactic Clusters

1.1 Query ResourceMetadata

(format value == "ascii" || "VOTable") &&
(type value == "catalogue" || "survey") && (subjectkeywords value == "Null" ^ ("Milky Way" || "Stars") && (coverage "decmin" value = NaN))

This should select DataSets which are tabular (not images or other such - this iteration) and contains measurments of sources (as distinct from a list of instrument pointings) (the suggested values may not be a complete list) It either has no subjectkeywords, i.e. the things it lists are unclassified, or they are explicitly classified as Milky Way or Stars.

The DataSets should have meaningful values of decmin, implying that they contains positional information. This means that we must fill in angular coverage for any data set containing celestial coordinates or object names which can be resolved by SIMBAD into coordinates.

1.2 From the DataSets meeting criteria in 1.1, query ResourceMetadata and sort DataSets accordingly (perform steps in order)

coverage "sourcedensity" descending order (ie high=good)
coverage "tablenrows" descending order for completeness or ascending order for speed
coverage "tablesize" ascending order
dataquality "astrometryerror" ascending order
dataquality "timingerror" ascending order

This is an optional prioritisation step to allow only the DataSets which are more likely to be useful to be selected, and/or to choose the order in which DataSets are queried or (the interim results) moved. Prioritisation could be applied at any later step. Other criteria like sensitivity could also be used. This implies that, for the errors, NaN counts as very large. It would be simplest if Null values were not allowed for sourcedensity and the size etc. of the DataSets

1.3 From the DataSets meeting criteria in 1.1, query UCD list

UCD == (StellarCluster || (Star && MembershipofStellarCluster^?))

This should select DataSets which either explicitly list stellar clusters, or which list stars and states whether they are members of a cluster.

3. RegistryQuery for existing proper motion and distance measurements

3.1 From the DataSets meeting criteria in 1.1, query UCD list

UCD == (ProperMotion)

AND

3.2 From the DataSets meeting criteria in 1.1, query ResourceMetadata

coverage "startdate" value = NaN

This should select DataSets with meaningful values of the epoch of observation (so proper motions could be calculated if not already explicitly catalogued).

5. RegistryQuery to enable colour-colour selection:

5.1 From the DataSets meeting criteria in 1.1, query ResourceMetadata

wavelengthrange (value = "ir" || value = "optical")

This should select DataSets which explicitly contain optical or IR measurements.

5.2 From the DataSets meeting criteria in 5.1, query ResourceMetadata ((wavelengthshort (value <x) && wavelengthlong (value > x)) ||
(wavelengthshort (value <y) && wavelengthlong (value > y)))

This should select DataSets which explicitly contain optical or IR measurements, or which cover at least part of the wavelength range x-y which covers the I, R and K bands as defined in the optical/IR.

AND

5.3 From the DataSets meeting criteria in 5.1, query UCD list

UCD = (Optical && (Photometry && ((I_Band || R_Band || numerical band spec.)))) ||
(IR && (Photometry && ((K_Band || numerical band spec.)))) ||
((Optical || IR) && (Colour && (I_Band || R_Band || K_Band || numerical band spec.)))

This should select suitable DataSets whether or not they have a detailed numerical description of the wavelength coverage (ideally all should have but this may take a while to implement) - or which already contain Colour information. In the case of e.g. K/R colour, I presume this would be classified as both IR and Optical.

-- AnitaRichards - 24 Apr 2003