IVOA Interop, Beijing, China, May IVOA Data Access Layer Working Group Sessions Doug Tody (NRAO/NVO ) Markus Dolensky (ESO/EuroVO) Data Access Layer Working Group I NTERNATIONAL V IRTUAL O BSERVATORY A LLIANCE

IVOA Interop, Beijing, China, May SIA V2 Planning

IVOA Interop, Beijing, China, May SIA V2.0 Motivation –SIA upgrade long planned to follow SSAP release –Major new release with upgraded interface and new functionality –Our purpose here is to establish priorities for a draft specification to follow Strawman Priorities –Simple access should continue to be simple –2ndGen query interface, query response metadata (Char etc.) –Expanded data access capabilities (image cubes) –Grid capabilities (stageData, bulk operations, etc.) –"Complex data" linkage (data associations, multiple views)

IVOA Interop, Beijing, China, May Query Parameters POS,SIZE –Syntax Currently POS = ",,...; " But in general POS can be any string –Features Support frames other than ICRS, e.g., galactic Rotated or non-rectangular regions are possible Multi-region support needed for large scale operations –Multi-region Input a separate table of regions (POST, acref, etc.) Index, ID, POS, SIZE, etc. for each region Link region IDs back to input table in query response

IVOA Interop, Beijing, China, May Query Parameters BAND, TIME –Basically unchanged from SSAP –BAND could be a range list for 2-D projection of a spectral cube –TIME could be a range list for 2-D projection of a time cube FORMAT –Probably unchanged from SSAP, SIAP V1 Other Query Parameters –SPATRES etc. - most should carry over –Collection, PubDID, etc. - apply equally well to images

IVOA Interop, Beijing, China, May Query Response Metadata DataID, Target, Curation, Characterization, etc. –Most of this should carry over without change –Characterization needs to be reviewed for the image case "Image" Metadata –Metadata specific to each dataset type is permitted –What do we need for images? –For SIA V1 this included Naxes, Naxis, scale, and so forth –Perhaps Char will provide most of this now –FITS WCS - how do we handle this? Metadata Extension –Carry over; probably nothing specific to images

IVOA Interop, Beijing, China, May Precision Data Access Purpose –Precise specification of generated virtual data –For example, mosaics, or slice/dice a large cube Already discussed in previous interops Subcube, 2D plane, 2D proj, slice, reprojection, etc. Issues –Image generation parameters specify the geometry and WCS of a new image this is another "declarative" approach to data access specify what we want, let service determine how to do it –Requires general WCS support including spectral and time axis

IVOA Interop, Beijing, China, May Grid Capabilities StageData –Front-end to UWS as already discussed –Images to be generated are described in a prior queryData –Submitted job may make any number of images in one job –Includes support for staging data (VOSpace etc.) Related Capabilities –Authentication –Secure access to proprietary data –Logging support Other –getCapabilities, getAvailability

IVOA Interop, Beijing, China, May SIA V2 Summary Key Challenges –Generalize POS,SIZE to support multiple regions, more general regions, while still providing simple ROI for common usage –Need more formal mapping of FITS WCS to our data models –Generalize image generation mechanism to support precision image cube access (requires WCS integration) –Integration of Grid capabilities –Complex data (dataset associations and views)

IVOA Interop, Beijing, China, May