2007-04-12/13 SNAP data model

Simulation data model

2007-04-12/13 SNAP data model

Overview

• Goal and approach

• Domain model

• Logical model

• Discussion

• Other data models– IVOA– Concrete

• Usage in query protocol

2007-04-12/13 SNAP data model

Goals

• Describe spatial simulations for SNAP ( SSSAP ?)

• Use in – Discovery (simulation registry)– Query phase in SSSAP protocol– Meta data in returned data

• See whether we can produce a model serving other types of simulations as well.

2007-04-12/13 SNAP data model

Modeling approach

• Step 1: Analyse “universe of discourse”, resulting in a domain model : – Application independent– Implementation (language) neutral (UML)

• Step 2: Specialise to requirements, create logical model– Application dependent– Implementation neutral (UML)

• Step 3: create mappings to implementation languages, physical model:– XML schema– Relational database schema

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Simulation domain model

• Based on “domain model for astronomy” http://www.ivoa.net/internal/IVOA/IvoaDataModel/DomainModelv0.9.1.doc

• Main areas/namespaces:– Experiment– Protocol– Phenomenology– Storage– Standards– Model

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Domain model overview

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Domain modelpackages

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Domain modelexperiment

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Domain modelprotocol

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Domain modelphenomenology

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Experiment:simulation Protocol::simulation

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Logical model

• Not aim to describe all details of simulations, nor all types of simulations

• Focus on those aspects of interest to – discover interesting SNAP services– query a SNAP service for interesting simulations– provide meta data for a data product produced by

SNAP service

• How to find out? Ask scientists (as well as ourselves)!

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Example questions

• What questions would you ask a database containing (meta-data about) simulations:– What is simulation about?– What physical processes are implemented?– What values do certain parameters have?– What observables are provided?– What are characteristics of observables?– What type of data products can be returned?– What special data products can be provided as well? – What special services are available on server?

2007-04-12/13 SNAP data model

Logical model

• For our purposes (SNAP), a simulation isthe execution of software that produces a

representation of a spatial system, and possibly follows its evolution in time by approximating the true physical processes of the system with numerical algorithms.

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Logical model(see wiki pageand doc)

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Discussion SNAP_DataModel.doc

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Relations to other DMs

• DM WG– Characterisation– Quantity (?!)

• Resource Registry WG– Resource Metadata

• Semantics WG– UCD – standard vocabulary– Ontology of astronomical object types

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Characterisation

• We have a generalisation of (part of?) characterisation– a priori and a posteriori– No support/fill, do we need it? How?– No accuracy/sensitivity, do we need it? How?

• How do we proceed?– use Characterisation patterns– use implementation

• ACTION ITEM – “tiger team” to complete this aspect of model

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Resource Metadata

• Registration of SNAP resources

• Registration of related services

• Description of simulations published through SNAP sufficient?

• ACTION ITEM – “tiger team” for proposing how/what to register

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Semantics

• Various usages of standard vocabularies, ontologies

• Are the current lists sufficient for SNAP+Simulation description/querying?

• What is missing?• ACTION ITEM

– “tiger team” to evaluate this– propose more concepts– push for getting such lists accepted in IVOA

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Quantity (?)

• Could this DM play a role in defining how different data products are stored? Can be retrieved?

• Possibly suggest standard representations for complex data structures.

• Possibly suggest bindings to various popular languages.

• Opinions...?

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Mapping of concrete models

• Need to validate our model by checking whether concrete models “out there” are properly supported– ITVO data model – Horizon data model – GalICS data model – Data model from OWLS-GIMIC HDF-5 files – GAVO hydrosims data model – Millennium database data model – Example input parameter files

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Usage of data model

• Query protocols– HTTP – ADQL

• Serialisation – XML schema– Relational database schema

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HTTP GET

• Parameter-value based• Not simple if underlying model complex (or

is it?)• At least not in one query use multiple

queries: drill-down• Requires more sophisticated (web)

applications, possibly session aware.• Useful to have this done in a centralised

meta data repository.

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ADQL

• SQL based

• Requires relational mapping (see later)

• Requires supporting a relational database as well as ADQL

• Again, useful to have a limited number of meta-data repositories (registry++?).

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Mappings (see doc)

• XML schema– Mapping prescription

(http://www.ivoa.net/twiki/bin/view/IVOA/VOResource010RevNotes)– Can be automated (XSLT or ArchitectureWare from

XMI files)• Relational model

– Simpler and rather many standards for OR mapping (JDO, Hibernate)

– For ADQL/TAP? need some extra files to provide database metadata

• If agree on mappings, both can be postponed until UML is done.

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How to proceed.

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TODO items

• Previously mentioned teams for ironing out certain issues wrt other IVOA efforts– characterisation– ontologies– registry model– quantity

• Test cases– map concrete models to SNAP model– implement services

• Gather feedback from community– explanatory document– questionnaire– incorporate comments– Euro-VO DCA TEG