September 13, 2004NVO Summer School1 VO Protocols Overview Tom McGlynn NASA/GSFC T HE US N ATIONAL V IRTUAL O BSERVATORY

September 13, 2004NVO Summer School2 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.

September 13, 2004NVO Summer School3 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 Request-Object Management Environment (ROME)

September 13, 2004NVO Summer School4 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, …

September 13, 2004NVO Summer School5 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

September 13, 2004NVO Summer School6 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

September 13, 2004NVO Summer School7 Semantic content IVOA identifiers –Scheme for providing unique identifiers for any thing that needs to be distinguished. Services, requests, … –ivo://authority/authority_controlled_string#sub-resource –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.flux;em.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

September 13, 2004NVO Summer School8 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

September 13, 2004NVO Summer School9 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.

September 13, 2004NVO Summer School10 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

September 13, 2004NVO Summer School11 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.