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#### A.9.1.1 Registry Query Panel

Registry Query Panel

The Registry Query Panel appears in all VO query windows (though by default the TAP window uses an alternative registry search panel) and allows you to search for entries in the Registry representing data services of the type appropriate to the window. Note that if you know the service URL for the service that you want to use, you don't need to use this panel at all; you can simply fill in the URL in the lower part of the window.

The top part of this panel contains the fields you can fill in to query the registry for services matching your constraints. This consists of the following parts:

Registry
  This determines the registry that will be queried for suitable data services. You can select from the available options, or enter a URL corresponding to some other registry service that you know about. The default is currently the GAVO registry, which at time of writing usually works pretty well, but other registries may have somewhat different data holdings. Some registries don't work very well, so you may have trouble if you use other ones.

  To the right of this box is a selector that allows you to choose between two registry protocol options: RegTAP and RI1.0, corresponding to the IVOA Relational Registry and Registry Interface 1.0 standards respectively. At the time of writing (June 2014), RI1.0 is being phased out, and RegTAP is recommended. It is in any case considerably faster and more reliable than RI1.0. Unless you are a registry enthusiast, sticking to RegTAP is recommended.

  The Update Registry List item in the Registry menu queries the currently selected registry for other registries, and adds more entries to the selector box as appropriate; the little round indicator between the URL and protocol selectors indicates progress of this query.

Keywords
  Fill this in with keywords appropriate to the services you want to find. The format is space-separated words, and there is no wildcarding. So for instance if you want to find services relating to quasars in Sloan data you could enter the terms "SDSS QSO". These terms are matched against certain fields of each registry entry (as determined by the Match Fields checkboxes below) of each registry entry to see if it matches. Usually one or two short words is the appropriate level of detail. If no keywords are filled in, all the appropriate services are retrieved. Some experimentation may be required to specify a query with a reasonable number of results; if your query returns no results, try fewer or more general terms, and if it returns too many, try more or more specific ones.
And/Or button
  This determines whether a registry entry is considered to match the chosen keywords if it matches all of them, or at least one of them. Clicking it toggles between "And" and "Or". The default is "And", meaning that all keywords must be matched (against any of the selected match fields) for a selection.
Match Fields
  This line contains a number of checkboxes which allow you to define which fields in each registry record will be compared against the keywords you have entered when looking for matches. The contents of the Short Name, Title, Subjects, ID and Publisher fields are visible in the table of results. Description is a free-form, often long, description of the resource; it can be useful, but can often accidentally contain text which causes unwanted matches. By default the Short Name, Title, Subjects and ID fields are matched - click the checkboxes to change the selection
Find Services button
  When the other fields have been filled in, hit the Find button and the registry will be searched to find data services that match the constraints you have given.

In some cases, when the window first appears, it will automatically query the registry for all known services of the appropriate type. This is currently the case for SIA and SSA services, since there is a manageable number of these. There are thousands of cone searches however, so for the cone search windows you need to fill in a query and submit it yourself. In either case, you can resubmit a query (hit the Cancel button first if necessary) to make another selection of registry entries.

When the query completes, a table of matching entries is displayed below the Submit button. The number of resources found is displayed at the bottom, labelled Resource Count. The table contains one row for each matching entry, i.e. each service of the appropriate type that you can submit your data query to. The columns in the table give a short name, title, description and some other information about each service. You can sort the table rows according to the entries in different columns by clicking on the column header; click again on the same header to reverse the sort order. A little up/down arrow in a column header indicates that that column is currently determining the sort order. You can adjust the columns which are visible using the Columns menu, or drag the columns sideways to change their order in the usual way.

You should select the service that you want to query for data by clicking on it. When this is done, you will see one or more rows appear in a second table underneath the first one. In most cases, this contains a single row which will be automatically selected. However, some registry entries have multiple data services associated with a single record - in this case you should select the appropriate entry from the lower table as well.

Once you have selected a data service in this way, its service URL will be entered in the lower part of the window (not shown in the figure above) and you are ready to perform the actual single or multiple data query.

If a SAMP hub is running (see Section 9), it is possible to exchange lists of resources between this window and other applications. If another application sends a suitable message to TOPCAT, and the resources are of an appropriate type, and the window is visible at the time, the received list can be loaded and displayed here, replacing any which are currently displayed. You can control whether incoming lists are accepted and displayed in this way using the Accept Resource Lists toggle, either using the checkbox just above the resource display panel, or using the corresponding item in the Interop menu. If you wish to send your selection to one or more other applications which can make use of them, use the Broadcast Resource List () or Send Resource List () options in the Interop menu.

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TOPCAT - Tool for OPerations on Catalogues And Tables
Starlink User Note253
TOPCAT web page: http://www.starlink.ac.uk/topcat/
Author email: m.b.taylor@bristol.ac.uk
Mailing list: topcat-user@bristol.ac.uk