NERC DataGrid and CSML NDG Team

CSML: Context NERC DataGrid: the integration problem –multiple organisations, formats, storage mechanisms (file, relational) –only commonality is data semantics

CSML – benefits of explicit semantics Aim is to be as explicit as possible about semantics of information classes Offer significant potential for advanced processing workflows Reduce representation errors (e.g. omitting key attributes) ‘Conventions’ approach is fragile

CSML – benefits of geospatial standards Interoperability!! Expanded user-base Enhanced ROI Compliance to emerging SDI infrastructures

e.g. SDI – EU INSPIRE Directive of EU, passed EP this month –10-year+ program, €1bn –Based on standards

The potential CSML CDM O&M ??? GEOSSWISINSPIRE

Background: ‘feature types’ Emerging ISO standards –TC211 – around 40 standards for geographic information –Cover activity spectrum: discovery  access  use A geospatial dataset… …consists of features and related objects… …in a defined logical structure… …delivered through services… …and described by metadata. ISO Domain Reference Model

[from ISO “Geographic information – Rules for Application Schema”] Background: ‘feature types’ Geographic ‘features’ –“abstraction of real world phenomena” [ISO 19101] –Type or instance –Encapsulate important semantics in universe of discourse Application schema –Defines semantic content and logical structure of datasets –ISO standards provide toolkit: spatial/temporal referencing geometry (1-, 2-, 3-D) topology dictionaries (phenomena, units, etc.) –GML – canonical encoding

Standards-based modelling The standards-based approach –“Conceptual modelling is the process of creating an abstract description of some portion of the real world and/or a set of related concepts.” (ISO 19101) Universe of discourse Feature types ISO Application schema ISO ISO The taxon name taxon 'ANTHOZOA',63.1,missing 'Scoloplos armiger',66.1,missing 'Spio filicornis',10,missing 'Spiophanes bombyx',60.3,missing 'Capitellidae',131.8,missing 'Pholoe',10,missing 'Owenia fusiformis',23.4,missing 'Hypereteone lactea',6.8,missing 'Anaitides groenlandica',13.2,missing 'Anaitides mucosa',6.8,missing ISO 19118

The “general feature model”

Governance in standards-based modelling The importance of governance –Information community defined by shared semantics –Need community process to manage those semantics (definitions, models, vocabularies, taxonomies, etc.) –e.g. CF conventions for netCDF files –Role of Feature Type Catalogues [ISO 19110] and registers [ISO 19135] Governance as driver for granularity –Remit / interest determines appropriate granularity –e.g. IOC, IHO, WMO abstractgenerichighly specialised feature types spectrum

CSML ambition The CSML ‘niche’ –set of base feature types for specialising or using as-is

What is CSML? British Oceanographic Data Centre British Atmospheric Data Centre ISO standards ‘Governance Principle’ Climate Science Modelling Language CSML application schema Conceptual model Schemas Tooling

CSML Version Two CSML v2 –More explicit/expanded feature types: Swath ProfileSeries  {Radar, Section, ProfileSeries} Lost ‘composite domain pattern’ –GML 3.2 (  ISO 19136) –removed ‘storage descriptors’ from core CSML schema –‘affordance’ (i.e. FT behaviour) –O&M

CSML and O&M OGC ‘Observations and Measurements’ An Observation is an Event whose result is an estimate of the value of some Property of the Feature-of-interest, obtained using a specified Procedure CSML

CSML AbstractFeature Provides common model for all CSML feature types Supports OGC Observations and Measurements model Each CSML feature: –has a type (with operations and required attributes), the ‘affordance’ concept –represents some physical ‘parameter’ (Phenomenon) –has a ‘value’ property which is a coverage (with domain and range) – the domain is often a subclass of ReferenceableGrid –may have additional attributes providing ‘reference’ spatio-temporal location parameters

CSML Abstract Feature

CSML ReferenceableGrid Implementation of ISO CV_ReferenceableGrid, missing from GML Subject of OGC GML Change Request (doc ) Analagous to CF – grid locations specified for each axis of CRS Efficiency allowed when CRS axis aligned with grid axis Supports both spatial and temporal (and compound) CRS

ReferenceableGrid subclasses

CSML v2 Feature Types Feature typeDescriptionExample PointFeatureSingle point measurement.raingauge measurement PointSeriesFeatureTime-series of single datum measurements at a fixed location in space. tidegauge, rainfall timeseries TrajectoryFeatureMeasurement along a discrete path in time and space. surface salinity along a ship’s cruise track; atmospheric aerosols along an aircraft’s flight path PointCollectionFeatureCollection of distributed single datum measurements at a particular time 2m temperatures measured at weather stations across the UK at 0600z. ProfileFeatureSingle ‘profile’ of some parameter along a vertical line in space. wind sounding, XBT, CTD, radiosonde ProfileSeriesFeatureTime-series of profiles on fixed vertical levels at a fixed location vertical radar timeseries, thermistor chain timeseries RaggedProfileSeriesFeatureTime-series of unequal-length profiles, but on fixed vertical levels, at a fixed location repeat daily balloon soundings of atmospheric temperature from the same location SectionFeatureSeries of profiles from positions along a trajectory in time and space. shipborne ADCP RaggedSectionFeatureSeries of profiles of unequal length along a trajectory in time and space marine CTD measurements along a ship’s cruise track ScanningRadarFeatureBackscatter profiles along a look direction at fixed elevation but rotating in azimuth weather radar GridFeatureSingle time-snapshot of a gridded field.gridded analysis field GridSeriesFeatureTime-series of gridded parameter fieldsnumerical weather prediction model, ocean general circulation model SwathFeatureTwo-dimensional grid of data along a satellite ground-path AVHRR satellite imagery

PointFeature

PointSeriesFeature

ProfileFeature

PointCollectionFeature

ProfileSeriesFeature

RaggedProfileSeriesFeature

SectionFeature

RaggedSectionFeature

SwathFeature

GridFeature

GridSeriesFeature

TrajectoryFeature

ScanningRadarFeature

CSML instances – semantic wrapper to persisted file-based data xlink recommended in GML for linking to external content, but no best practice established CSML wants to use this for linking to storage desriptor for coverage domain/range ‘simple xlink’ properties: –role: indicates a property of remote resource –arcrole: describes meaning of remote resource <someGMLElement xlink:arcrole="hasRemoteContentEmbeddedAt#localXpath" xlink:href="storageDescriptor#portion" xlink:role="storageSchemaIdentifier" xlink:show="embed" xlink:actuate="onRequest | onLoad"/>

CSML instances – xlink example Geodetic longitude x Linear <csml:coordAxisValues xlink:arcrole=“ xlink:href=“file://myfile.nc#lon” xlink:role=“ xlink:show=“embed”> <csml:coordAxisValues xlink:arcrole=“ xlink:href="CSMLStorageDescriptorExample.xml#coapec_u_2" xlink:role= " xlink:show=“embed”>

CSML Storage Descriptor