VO Protocols Overview

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THE US NATIONAL VIRTUAL OBSERVATORY
VO Protocols Overview
Tom McGlynn NASA/GSFC
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Summary

• What are the VO agreements that are used within
  by VO clients and services?
• Set the context for building blocks that
  subsequent talks will describe in detail.
• Show how the protocols work together.

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Protocol List

• VOTable
• FITS
• Cone Search Protocol
• Simple Image Access (SIA) Protocol
• Simple Spectral Access (SSA) Protocol
• SkyNode
• Astronomical Data Query Language (ADQL)
• Uniform Column Descriptors (UCDs)
• Space-Time Coordinates (STC)
• IVOA Identifiers
• VO Registry
• Resource Metadata
• Registry Access Protocols
• OAI
• VOEvent
• NESSSI
• VOSpace
• PLASTIC
• Common Execution Architecture

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Formats

• VOTable
• XML format for tabular information
• Catalog query results
• List of images or spectra
• Lists of resources
• Includes UCDs for columns
• FITS
• Standard astronomical binary data format
• Images, spectra,

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Data Access Protocols

• Cone search
• Simple query around a given region
• Returns VOTables
• Simple image access
• What images overlap a given region?
• Create me an image of this region.
• First step produces VOTables with links to image
• User downloads images as FITS in second stage
• Simple spectral access
• What spectra are available within this region
• More sophisticated than SIA (includes support for
  Data Models) but uses comparable framework
• SkyNode
• SOAP Web-Service based
• Sophisticated access to tables
• Supports distributed queries
• Uses ADQL
• Should eventually subsume Cone-search

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Query languages

• Astonomical Data Query Language (ADQL)
• Enhanced version of SQL to support astronomical
  queries
• Positional cross-correlations (XMATCH)
• Complex regions on the sky (REGION)
• Both SQL-like and XML representations

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Semantic content

• IVOA identifiers
• Scheme for providing unique identifiers for any
  thing that needs to be distinguished. Services,
  requests,
• ivo//authority/authority_controlled_stringsub-re
  source
• Used in registries and other protocols
• Resource metadata
• Standardized format for the description of a
  service, data collection, facility.
• XML format based on the Dublin-core metadata
  descriptions for published resources.
• Used inside registries.
• Uniform Column/Content Descriptors (UCDs)
• Standardized names for table columns with
  relatively high degree of specificity.
• pos.eq.ra or phot.fluxem.ir
• Used in VOTables and by Cone search and SIA
• Space/Time Coordinates
• Way of specifying points or regions of
  space-time.
• Can be simple or very complex
• Used in ADQL and VOEvent

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Discovering Resources

• Registry
• Collection of resources that users can find
  included Cone Search, SIA, SSA and SkyNodes.
• User access via registry access protocol
• Registry-registry communication via OAI
• Some publishing registries are meant to be seen
  only by other registries
• Registry access
• How users query the registry
• In standards process
• Open Archive Interface (OAI)
• Library community standard
• Registry-registry communication to ensure that
  all registries are up to date.
• VOEvent
• VO protocol for publishing and receiving notice
  of transient/urgent events
• Describes events using STC

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Accessing and Controlling Computer Resources

• NESSI
• NVO Extensible, Scalable, Secure Service
  Infrastructure
• Provide access to protected resources, especially
  Grid computational resources.
• Make it easy to do simple things.
• First implementations just coming on-line
• VOSpace
• Access to storage resources in a standardized
  way.
• PLASTIC
• Platform for Astronomical Task InterCommunication
• Applications publish and receive notifications of
  events from other applications (e.g., selection
  of a given object) to enable coordinated actions.
• TOPCAT Aladin
• Deployed but still experimental.
• Common Execution Environment (CEA)
• Script/pipeline environment with security and
  such incorporated (Astrogrid)
• ROME
• Handle and schedule tasks that involve remote
  resources.

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Immediate access to data near a recent event
using DataScope

• VOTable
• FITS
• Cone Search Protocol
• Simple Image Access (SIA) Protocol
• Simple Spectral Access (SSA) Protocol
• SkyNode
• Astronomical Data Query Language (ADQL)
• VO Registry
• Resource Metadata
• Registry Access Protocols
• OAI
• Uniform Column Descriptors (UCDs)
• Space-Time Coordinates (STC)
• IVOA Identifiers
• VOEvent
• NESSI
• VOSpace
• Common Execution Architecture
• Request-Object Management Environment (ROME)

Used currently Will be used Could be used
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• Event is detected by VOEvent publisher who
  publishes the event.
• VOEvent notification received by CalTech VOEvent
  consumer.
• STC position of VO event noted and used to
  initiate DataScope request at HEASARC.
• DataScope sends request to VO Registry at ST ScI
  to find appropriate services.
• DataScope sends out Cone and SIA (soon SSA and
  SkyNode) requests to registered services and gets
  back VOTables of results.
• SIA VOTables index FITS files
• DataScope sends FITS and VOTables to user or
  other VO-enabled tools.