UCD 、 SIA 、 CS 、 SSA 、VOInterface, …

Chenzhou CUI

Agenda

• Unified Content Descriptor • Simple Image Access Protocol• Simple Cone Search• Simple Spectrum Access Protocol• VOInterface• Other IVOA documents

Ontology ，本体

Ontology

• Short answer: • An ontology is a specification of a conceptualization.

• The word "ontology" seems to generate a lot of controversy in discussions about AI. It has a long history in philosophy, in which it refers to the subject of existence.

• In the context of knowledge sharing, I use the term ontology to mean a specification of a conceptualization. That is, an ontology is a description of the concepts and relationships that can exist for an agent or a community of agents.

• Tom Gruber <gruber@ksl.stanford.edu>

• For pragmetic reasons, we choose to write an ontology as a set of definitions of formal vocabulary. Although this isn't the only way to specify a conceptualization, it has some nice properties for knowledge sharing among AI software. Practically, an ontological commitment is an agreement to use a vocabulary in a way that is consistent (but not complete) with respect to the theory specified by an ontology. We build agents that commit to ontologies. We design ontologies so we can share knowledge with and among these agents.

• Tom Gruber <gruber@ksl.stanford.edu>

Unified Content Descriptor

• IVOA controlled vocabulary for describing astronomical data quantities

• The Unified Content Descriptor (UCD) is a formal vocabulary for astronomical data that is controlled by the International Virtual Observatory Alliance (IVOA).

• UCD 是介于自然描述和结构模型之间的词表

Interoperability as a goal

• The major goal of UCD is to ensure interoperability between heterogeneous datasets. The use of a controlled vocabulary will hopefully allow an homogeneous, non-ambiguous description of concepts that will be shared between people and computers in the IVO.

UCD Syntax• A UCD is a string which contains textual tokens tha

t we shall call words, which are separated by semicolons (;). A word may be composed of several atoms, separated by period (.) characters. The order of these atoms induces a hierarchy.

• 字母、数字、连字符、下划线• 不分大小写• 中间不允许有空格

– phys.temperature– pos.eq.ra;meta.main– meta.id;src– phot.flux;em.radio;arith.ratio– PHot.Flux;EM.Radio;ivoa:arith.Ratio

UCDList • The UCD1+ controlled vocabulary Version 0.2• All existing UCD1+ words are grouped into 12 main c

ategories.– arith(arithmetics)– em(electromagnetic spectrum)– instr(instrument)– meta(metadata)– obs(observation)– phot(photometry)– phys(physics)– pos(positional data)– spect(spectral data)– src(source)– stat(statistics)– time(time)

UCD Tools

• UCD tree browser: – Java – Javascript

• Find UCD from keywords

Simple Image Access Protocol• This specification defines a protocol for retrieving ima

ge data from a variety of astronomical image repositories through a uniform interface. The interface is meant to be reasonably simple to implement by service providers. A query defining a rectangular region on the sky is used to query for candidate images. The service returns a list of candidate images formatted as a VOTable. For each candidate image an access reference URL may be used to retrieve the image. Images may be returned in a variety of formats including FITS and various graphics formats. Referenced images are often computed on the fly, e.g., as cutouts from larger images.

• Virtual Sky: image created on-the-fly• pre-existing, statically sized atlas

SIA Types

1. Image cutoff service (no resample)2. Image mosaic service (resample and repro

ject, pixel generation, etc)3. Atlas image archive (is not capable of dyn

amically cutting out)4. Pointed image archive (specified source)

Requirements for Compliance

• Image query web method• Image staging web method• Image retrieval web method• Image service must be registed• • Refer to the specification

Simple Cone Search

• Compliance REQUIRES• <BaseURL>?RA=3D....&DEC=3D....&SR=3D....

• Response: VOTable• Error message• Metadata information (Registry)

– http://virtualsky.org/servlet/cover?CAT=messier&RA=220&DEC=40&SR=10

Refer to the specification

Simple Spectrum Access Protocol

• The Simple Spectrum Access SSA specification defines a uniform interface to 1d spectra and SEDs. It shares many similarities with the Simple Image Access SIA (Tody et al. 2002) and Cone Search CS specifications.

SSA

• In order to be SSA compliant a service MUST support the following three query/response formats:

1. A metadata query mode returning the usage of an SSA service encoded as VOTable document.

2. A spectrum query mode returning a table of matching observations including access references.

3. A getter method to access an individual spectrum or set of SEDs.

Refer to the specification

IVOA Support Interfaces Version 0.21

• This document describes the minimum required interface to participate in the IVOA as a web service.

• Some which these services should provide. The word

• SOAP, CGI,

• SI-1 “getRegistration” interface.

• SI-2 “RegistrationChangedOn” interface.

• SI-3 “getAvailability” interface.

• SI-4 “HarvestWebLog” interface.

• SI-5 “HarvestServiceLog” interface.

• Refer to the specification

Other IVOA documents

Virtual Observatory Architecture OverviewVersion 1.0

• This document provides a high-level conceptual overview of the IVOA-supported architecture of Virtual Observatories that has emerged over the last few years.

• IVOA Architecture

Document Standards

• This document describes the types of official IVOA documents and the process by which documents are advanced from Working Drafts to formal Recommendations.

• Document Standards

Space-Time Coordinate for the Virtual Observatory

• This document provides a complete design description of the Space-Time Coordinate (STC) metadata for the Virtual Observatory. It explains the various components, highlights some implementation considerations, presents a complete set of UML diagrams, and discusses the relation between STC and certain other parts of the Data Model. Two implementations are discussed: XML Schema (STC-X) and String (STC-S, also known as LinearSTC).

Sky Event Reporting Metadata (VOEvent)

• The objective of the VOEvent effort is to define the content and meaning of a standard information packet for representing, transmitting, archiving, and publishing a discovery of an immediate event in the sky. We will call this packet VOEvent.

• VOEvent 0.3

Data Model specificationsDefinition Leader Team

Group 1

Spectra 1-dimensional spectra Jonathan McDowell

Quantity Value/unit/uncertainty Jonathan McDowell

Observations Big picture, and observing metadata Alberto Micol

Transforms WCS, units, etc. on quantities Dave Berry

Catalogs Catalogs Pedro Osuna

Group 2

Inteferometry Particularly, radio issues Peter Lamb

Simulations Theory in the VO Gerard Lemson

Group Martin?

Passband Modelling Passbands Martin Hill

Error/Accuracy Representing Errors Martin Hill

Spectra An alternative (exercise-only) spectra model Martin Hill

Asynchronous activities proposal

• Asynchronous activities are when an operation on a web service starts some activity and returns immediately, leaving the activity running. This asychronicity is useful in making a robust VObs and is already used in some VObs prototypes. A proposal for managing the activities is presented to IVOA:

• AsynchronousActivityProposal • Comparison of systems for contextual web services • Universal worker service: a formalization of the proposal

Single-Sign-On Proposal

• We need single-sign-on (SSO) authentication for the VObs. Conventional wisdom is that this should be done with digital signatures, but the standards for these signatures allow many different approaches. A proposed profile is now available for how the VObs might do SSO.

• Original SingleSignOnProposal • Draft of IVOA note introducing the profiles. • Draft of message specification for SSO.

VO Web Services Basic Profile Proposal

• This document describes rules to take into account when implementing Web Services. It explains also how to check the conformance to these rules. It can be resumed as a "Guideline for VO Web Services interoperability" or a "How to provide interoperable VO Web Services".

• Draft of VO WS Basic Profile.

VO Store Proposal

• This document is a discussion document toward forming a vostore speicifaction for interop of file/data sharing between VO Services.

• Draft VOStore spec/Discussion doc.