How Do I Use GAVO's Web Interface to the Registry?

This document is intended to help you discover the features of GAVO's Web Interface to the Relational Registry (WIRR).

Intro

To explore the vastness of the Virtual Observatory (VO) and to discover resources matching your taste and interest, GAVO provides a web-based user interface to the VO registry (the standard for the registration of VO resources).

Search Form

The heart of our user interface is a search form that allows for sending customised queries to the relational registry. Adder and subtractor buttons will help you to build and modify your query. By pressing the “Run query” button, your request is submitted to the registry.

The star () next to the “Run query” button lets you bookmark the current form. This should come in handy to store and communicate preset queries.

Search By...

Text Fields

The database will be queried for resources which contain the expression you've entered either in their description, in their title, or in the information about their creator(s).

Service Capability

Select the type of service (cone search, images, spectra, ...) you are interested in from the list provided by the search form.

Waveband

Select a waveband region from the list provided by the search form.

Subject

The database will be queried for resources which contain/do not contain the expression you have entered (e.g. “galaxies” or “quasars”) in the “subject” field of their metadata.

Creator

The database will be queried for resources which contain/do not contain the expression you've entered in the metadata about their creator(s).

Column UCD

UCD refers to “Unified Content Descriptor”. UCDs form a controlled vocabulary for describing astronomical data quantities. The descriptor for the right ascension in equatorial coordinates, for instance, is “pos.eq.ra” The UCD resolver might help you to find appropriate descriptors.

Resource

Enter an IVO Identifier (“IVOID”), submit the form, and the database will be queried for resources related to the one for which you've typed the ID into the text field.

Title

The database will be queried for resources which contain/do not contain the expression you've entered in their title.

Description

The database will be queried for resources which contain/do not contain the expression you've entered in their description.

Updated

This enables you to search for resources updated within the last x days or after a certain date. Valid date strings are for example 2011-12-24 or 2012-02-29T18:20:04.

Detail Value

This type of search has been implemented as a key-value search (XPath-detail value). For a given set of XPath keys, you can search for resources with matching detail values.

IVOID

The database will be queried for resources which contain/do not contain the expression you've entered in their IVO Identifier.

Results from the All-VO Search

Query results can be web services (WEB), TAP services, cone search services (SCS) or services for images (SIA) and spectra (SSA).

The results are provided as a list giving the titles, the service types and the information on how to get in touch with the people responsible for a specific resource. A click on the arrow at the beginning of each row opens a second level providing more detailed information about the resource like a description, the last update and the “ivoid”.

While a web service can be accessed by clicking on the given URL, you usually want to send results of the other types to a dedicated desktop client. For this purpose, you will need to launch a Web SAMP Hub, e.g. “TOPCAT” (SAMP is short for “Simple Application Messaging Protocol”). Then connect to the SAMP hub and send the list of resources you've found to your preferred client(s).

Query History

The queries sent to the database are stored and returned on demand. To browse the history, use the “Query History” arrows which work in the same way as the backward and forward arrows of your web browser. Unfortunately, the query history gets lost while reloading the web page.

[Query History]

Relationships

In the Virtual Observatory, there may be relations between resources. These can be things like mirror-of or derived-from, but more importantly served-by (and service-for). The story behind the latter two is that some resources are just data -- the data center says, essentially: "Look, I have this wonderful data collection with this description, and the table structure is this." For a user, that's not too useful, since there's no information on how she can get that data.

To fix this, the data provider declares that the data collection is “served-by” some other service, TAP, for example, or maybe SIAP if a single image server exposes data from multiple collections.

In WIRR, if a resource has relations, we show an icon -- [Related Icon] -- if a resource has any related resources at all. Click on that icon, and the form will be changed to show all related resources.

Since the served-by relation has a special role -- for resources without capabilities, it's the only way you'll get at the data --, we show a special icon -- [Served Icon] -- as soon as at least one of the relationships are services for the result is a service for the resource. Click on those to figure out the access options for the data.

Example Query (WIRR plus TOPCAT)

Let us consider you want to query the VO for TAP services. Ah, there is a preset condition for exactly this case! So click on “TAPServices” in the sidebar, see how the search form will change to “Service Capability is TAP (SQL)”, and press the “Run query” button. You will get a list of resources providing TAP capabilities.

Now try to connect to a SAMP hub. Ok, no one is running on your desktop and you'll get informed about this circumstance by an alert message. After you have started TOPCAT, you should get connected to its hub.

Try to click on “Send... TAP (SQL) services”. Another info window says: “... TOPCAT was not in a suitable state to make use of it (perhaps suitable windows were not open)... ”. Then open TOPCAT's “Table Access Protocol (TAP)” window and try to resend the list.

TOPCAT is loading the resources found by you via WIRR? Great... now you are ready to use TOPCAT's TAP client to cross-match catalogues, to select the brightest stars in a certain region of the sky, or to look at the locations of potential neutrino sources in the universe.

Hint

GAVO's web interface to the relational registry needs JavaScript to work