Presentation on theme: "NVO Summer School 20081 VO Protocols and Jargon Overview Tom McGlynn NASA/GSFC T HE US N ATIONAL V IRTUAL O BSERVATORY."— Presentation transcript:
NVO Summer School 20081 VO Protocols and Jargon Overview Tom McGlynn NASA/GSFC T HE US N ATIONAL V IRTUAL O BSERVATORY
NVO Summer School 20082 Summary What are the VO agreements and tools 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.
NVO Summer School 20083 VO Protocols and Jargon Data Formats –VOTable –FITS –XML Data Access –Cone Search –Simple Image Access (SIA) –Simple Spectral Access (SSA) –Table access/SkyNode Astronomical Data Query Language (ADQL) (extends SQL) Semantics –Uniform Column Descriptors (UCDs) –Space-Time Coordinates (STC) –IVOA Identifiers Registry –Resource Metadata –Registry Protocols –OAI VOEvent NESSSI VOSpace PLASTIC/SAMP
Services Discovery portal: suite of collaborating tools to find data. –Registry: keyword search interface to registry db –SimpleQuery: Web tool to search and filter tables –Inventory: find data near sets of positions –DataScope: find everything near a given position –VIM: VO Integration and Mining-Combine data from multiple sources –Table converters/wizards –VOClient: Work from the command line. NOAO Portal: Graphical interface to VO data iPortal: Access to VO through mobile devices TOPCAT: CLI tool to manipulate tables VOPlot: CLI tool to plot VOTable data VOStat: Web tool to do statistics of VO data. WESIX: Web tool to extract and correlated objects from images. OpenSkyQuery: Web tool to query many on-line tables WCSFixer: Determine exact geometry of images. NVO Summer School 20084
5 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, … XML (eXtensible Markup Language) –Industry standard –Hierarchical –Extensible
NVO Summer School 20086 Data Access:Cone Search Simple query around a given region Returns VOTables Examples: What observations has Spitzer made of the Antennae? How many x-ray objects are within 30 of Abell 1656?
Data Access: 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 V1.0 is widely deployed. V2.0 is under development. Examples: Find all Chandra X-ray images near the Galactic center. Ask SkyView for an I/R cutout of the Orion spur. NVO Summer School 20087
Data Access: Simple spectral access What spectra are available within this region More sophisticated than SIA (includes support for Data Models and more complex criteria) Some services beginning to appear. Examples: Does HST have an FOS spectrum for this star in this wavelength band? NVO Summer School 20088
Data Access: Table Access Protocol and SkyNodes Table Access Protocol –Standardized access to complex queries of remote tables –Currently under development –Uses ADQL and simpler queries SkyNode –SOAP Web-Service based –Sophisticated access to tables –Supports distributed queries –Uses ADQL –Many operational nodes but should eventually be subsumed in TAP. NVO Summer School 20089
10 Query languages SQL: Structured query language. Industry standard to generating and extracting information from tables –Widely supported in free and commercial products (Oracle, Sybase, MySQL, Postgres, …) Astonomical Data Query Language (ADQL) –Enhanced version of SQL to support astronomical queries Positional correlations Complex regions on the sky –Under rapid development
NVO Summer School 200811 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 many 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
NVO Summer School 200812 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. –Publishing registries sometimes meant to be seen only by other registries Registry access –How users query the registry –Standard adopted and recently implemented. 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
NVO Summer School 200813 Access, Control and Communication NESSSI –NVO Extensible, Scalable, Secure Service Infrastructure –Provide access to protected resources, especially Grid computational resources. VOSpace –Access to storage resources in a standardized way. –Standard agreed. Some implementations available. –Promotes scripting of VO access. PLASTIC/SAMP –Platform for Astronomical Task InterCommunication (prototype protocol) –Simple Application Messaging Protocol (permanent standard) –Applications publish and receive notifications of events from other applications (e.g., selection of a given object) to enable coordinated actions, e.g. TOPCAT – Aladin –Many PLASTIC services deployed. SAMP protocol currently under review.
Portals NVO Data Discovery Portal: Find and get NVO data quickly. NOAO Portal: Visualize relationships of data. iPortal: NVO on cellphones and iPods. NVO Summer School 200814
Some popular tools WCSFixer: Web interface to correct errors in geometry of image. WESIX: Find objects in image then cross-correlate with other catalogs TOPCAT: Java based tool to get, manipulate and display tables. Aladin: Java based tool to get, manipulate and display images VOPlot/VOStat: Plotting and statistics for VOTables OpenSkyQuery: Query and cross-correlate many VO datasets NVO Summer School 200815
Miscellaneous Jargon Web Service: Web-based application intended for use by programs (possibly in addition to interactive use) REST: Representational State Transfer ~ Using stateless interfaces to access Web. Similar to GET based CGI. SOAP: Simple Object Access Protocol –Not so simple XML-based method for Web services. NVO Summer School 200816
How does it work together? Example: VOEventnets use of DataScope to gather information on recent events: –http://voeventnet.caltech.edu/http://voeventnet.caltech.edu/ Use first HTML feed to get link to event 323542 (from earlier today) Click on View data link. NVO Summer School 200817
NVO Summer School 200818 Immediate access to data near a recent event using DataScope VOTable FITS Cone Search Protocol Simple Image Access (SIA) Protocol VO Registry V OClient Resource Metadata Registry Access Protocols Uniform Column Descriptors (UCDs) Space-Time Coordinates (STC) IVOA Identifiers VOEvent
NVO Summer School 200819 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.