VO Data Access Layer IVOA Cambridge, UK 12 May 2003 Doug Tody, NRAO

Data access/analysis portal Link between client (user) data analysis software and the VO Enables distributed multiwavelength data access and analysis Key longer-term goals: –Integrate everyday data analysis with VO –Achieve a scalable VO architecture (same software used in multiple contexts)

DAL Scope: Software Service data access protocols –Catalog, image, spectrum, etc. Service frameworks – Virtual data generation and manipulation, grid computing Client side integration –API, Web Services client, components, etc. Test cases and demonstrations Denotes first year priority

DAL Scope: Types of data Source catalog Image Spectrum, SED Time series Event and visibility data Key challenges –DAL depends upon registry, query, UCD, DM, representation, etc. –Keep it simple; lower the bar for service implementors

Goals for this meeting Agree on DAL scope, WG scope –this will be our kick-off meeting Strawman data service architecture –what services are required? (e.g., extend image model, add spectra) Define roadmap for next year –drivers, priorities, goals of the partners –define Y1 standards development efforts –test cases and demos Example –SIA V1.1+V2, SSA V1, better RG/DM/UCD/QL integration, web services, test cases

DAL Agenda TimeActivityComments 10:00 Intro/Goals Review agenda 10:15 Scope/Priorities/Architecture What standards are needed; common elements, protocols 11:00 BREAK 11:30 Spectral Data Access Use cases, priorities; image model vs 1D spectrum, FITS/XML 13:00 LUNCH 14:00 SIA Enhancement Update on Aladin/CDS integration; priorities 15:00 Roadmap Drivers, priorities 15:30 BREAK 16:00 Roadmap Standards efforts, test cases, demos; standards process 17:00 CLOSE

Goals for this meeting Agree on DAL scope, WG scope –this will be our kick-off meeting Strawman data service architecture –what services are required? (e.g., extend image model, add spectra) Define roadmap for next year –drivers, priorities, goals of the partners –define Y1 standards development efforts –test cases and demos Example –SIA V1.1+V2, SSA V1, better RG/DM/UCD/QL integration, web services, test cases

Existing DAL Prototypes Cone search, SIA (NVO) Jodrell Bank – imaging online from Merlin data (Anita Richards) CVO – WFPC assoc, ROSAT, 2QZ (spectroscopic survey) – generic DA service for all data (query is separate); different service instances, obey same interface AUS/VO – HIPASS, ATCA archive, MACHO, SUMSS, 2DF GRSS – Web query i/f

Existing DAL Prototypes AVO –SIA, IDHA (all images) AstroGrid –HDX (Starlink) – mainly data model, not much data access yet –Also solar data, space physics data

DAL Portal Concept Link between client (user) data analysis software and the VO Enables distributed multiwavelength data access and analysis Key longer-term goals: –Integrate everyday data analysis with VO –Achieve a scalable VO architecture (same software used in multiple contexts)

DAL Scope: Software Service data access protocols –Catalog, image, spectrum, etc. Service frameworks – Virtual data generation and manipulation, grid computing Client side integration –API, Web Services client, components, etc. Test cases and demonstrations Denotes first year priority

DAL Scope: Types of data Dataset (add later) –Query for any type of data in a given ROI –Use other data access services to drill-down to actual data Source catalog –May need simplified catalog query in DAL portal –More sophisticated catalog operations elsewhere in VO Image –2D sky images, spectral data cubes, long slit spectra –Access to raw data via VO framework –Data model issues, representation (FITS, Graphic, XML) –Sparsely sampled images including IFU data Spectrum, SED Time series (later?) Event and visibility data (later?) Key challenges –DAL depends upon registry, query, UCD, DM, representation, etc. –Keep it simple; lower the bar for service implementors

DAL Architecture Data Access Services –Multiple services One service for each view of the data At a high level may not need to differentiate data –Integration of common elements of services –Can sometimes view the same data via different services E.g., and event list or visibility dataset viewed as an image –Simple services for most common cases

Application DAL Client Adapter DAL Service Simple Server Grid Service Analysis Component Data Mediator Component Data Access Framework Client Portal Service Protocols VO Data Access Layer Architecture

DAL Services Key common elements –Registry (caches resource and service data) –Query syntax and capabilities –Metadata –Data models –Data representation (e.g., VOTable)

First cut at priorities for Y1 SIA V1.1 –Same as now with minor enhancements Simple spectral access –Emphasize 1D and SED SIA V2.0 –General image model (spectral data cubes etc.) –Explore ways to structure metadata (table vs hierarchical) Better integration with VO standards –Query standards, registries, MD(UCDs), DM, data representations First steps for event, visibility data –E.g., metadata standards to publish raw data

Spectral Data Access Goals / Use Cases –discover, retrieve, display spectra for some object –discover, retrieve, display SED for some object –1D science spectrum for analysis, e.g., classification –multi-wavelength spectral combination –Generate spectra on the fly from grism/radio/HE data –??

Spectral Data Access Priorities –1D science spectra –SEDs –spectral image cubes (2 spatial + 1 energy) –2D science spectra (slit spectra) –??

Spectral Data Access Key Issues –general 3/4D image model vs simple 1D/SED –two services versus 1 –FITS vs XML (VOTable) both should be available for 1D spectra, SEDs (also graphic) Would need a new FITS standard for 1D spectra to use FITS here –??

SIA Evolution Interface concepts –roadmap: V1.0, 1.1; V2.0 –separation of query/discovery and access –types of services: atlas, pointed, cutout, mosaic –image generation parameters: query ROI supplies default –full specification of IGP possible for mosaic services

SIA Evolution Feedback on SIA V1.0 –Aladin/CDS integration (Francois)

SIA – Proposed Enhancements Registry integration Image Attributes –Image provenance and identification - 1 –Spectral bandpass (already present) - 1 –Spatial bandpass - 3 –Resolution - 1 –Limiting flux - 2 –Image type (future- v2) –Time of observation (1) –Default for case where there are multiple versions of same dataset Image Query –Use of image attributes to refine query (e.g., band) –POS, SIZE generalization? Coordinate frameworks

SIA – Proposed Enhancements Others –Support image compression in access protocol

Second cut at priorities for Y1 SIA V1.1 –Same as now with minor enhancements Simple spectral access –Emphasize 1D and SED SIA V2.0 –General image model (spectral data cubes etc.) –Explore ways to structure metadata (table vs hierarchical) Better integration with VO standards –Query standards, registries, MD(UCDs), DM, data representations First steps for event, visibility data –E.g., metadata standards to publish raw data Web services versions of DAL services

Drivers/Priorities IAU demo July 03 –Add registry support –Add Aladin, other SIA services –Integrate SIA registry into clients (Aladin, DIS, etc.) AAS, AVO demos January 04 –Web services versions of services?