Page 1 A Proposal for a Reference Implementation of the WMO Core Metadata Profile based on ISO-19115/19139 3 rd May 2006 by Jeremy Tandy, UK Met Office.

A Proposal for a Reference Implementation of the WMO Core Metadata Profile based on ISO-19115/19139 3 rd May 2006 by Jeremy Tandy, UK Met Office Jürgen Seib, Deutscher Wetterdienst Michael Burek, National Center for Atmospheric Research

A revised WMO Core Metadata Profile WMO Core Metadata Profile … ISO 19115 compliant? (also note that the standard itself has undergone some revision: ISO 19115:2003/Cor. 1:2006) Motivation version 0.2 is NOT compliant to ISO 19115 XML schemas of version 0.2 are bespoke UML model for WMO extensions does NOT exist

ISO 19115 compliance WMO Core Profile v0.2 breaks the extension rules defined in ISO19115 Annex C WMO encoding does not match ISO 19115 Changes to ISO 19115 (extensions) not in WMO- governed namespace Examples: Cardinality restricted Optional attributes removed … and much worse … (DQ_DataQuality) Further issues were noted in the WMO IPET-MI report prepared by Clemens Portele

A revised WMO Core Metadata Profile Characteristics of WMO metadata documents simple human readable (optionally) self-contained; i.e. the metadata record *should* be able to be expressed as a single document multilingual XML-validity should imply semantic correctness ISO 19115 compliant community profile

ISO 19115 - Extensions How do we create an ISO 19115 compliant metadata profile? Guidance: ISO 19115 Annex C: Metadata extensions and profiles ISO 19115 Annex F: Metadata extension methodology In order to ensure interoperability beyond the community where the extensions are implemented: a)You must document the extension via the extension metadata described in ISO 19115, and b)Add an isoType attribute to the class indicating which ISO 19115 class was sub-classed

ISO 19115 Clause C.2: Types of extensions adding a new metadata section creating a new metadata code list to replace the domain of an existing metadata element that has free text listed as its domain value creating new metadata code list elements (expanding a code list) adding a new metadata element adding a new metadata entity imposing a more stringent obligation on an existing metadata element imposing a more restrictive domain on an existing metadata element

ISO 19115 Clause C.4: Rules for creating an extension the name, definition or data type of an existing element can not be changed a new element may include extended and existing metadata elements as components metadata elements can be more stringent domains can be more restrictive the use of domain values can be restricted code lists of type «CodeList» can be expanded an extension shall not permit anything not allowed by the standard

Rules for creating a profile check registered profiles adhere to the rules for defining an extension A profile shall include: the core metadata all mandatory metadata elements all conditional metadata elements, if the dataset meets the condition use UML diagrams to describe a profile use your own namespace publish the profile

WMO namespace namespace: collection of names, identified by an URI reference is needed for extensions XML schemas of WMO extensions should reside in the http://www.wmo.int/metadata/2006 namespace xmlns:wmo = http://www.wmo.int/metadata/2006

So where do we go from WMO Core v0.2? 1.From the extension rules its clear that WMO Core v0.2 has problems 2.Furthermore, even *before* we extend ISO 19115 we need to identify an XML encoding of the content model ISO 19115 is an abstract specification … IT specifies what information is required but not how to encode it We developed our own XML encoding of ISO 19115 – as did many others Interoperability is impaired by having numerous inconsistent encodings of ISO 19115 …

The ISO standard 19139 XML schema implementation for ISO 19115 provides a common specification for describing, validating and exchanging metadata defines implementation guidelines for general-purpose metadata includes XML schema implementations of other ISO 191xx series (including ISO 19136 / GML) according to ISO 19118 Geographic Information – Encoding fulfils 99% of the needs for a WMO metadata standard

WMO metadata profile – key elements Whilst ISO 19139 resolves a large proportion (99%?) of metadata-related concerns from the WMO community … there are still a number of outstanding elements worthy of discussion: 1.Time 2.Internationalisation / multilingual support 3.Codelists and keywords 4.Service metadata 5.Catalogues – incl. Feature Catalogues

The future? Whilst it is recommended that we adopt ISO 19139 as the default encoding for WMO Core metadata … We must ensure that WMO Core is fit for purpose within the WMO community – where the existing ISO standard information models and encodings are not appropriate we should *adapt* them to our needs (e.g. ISO 19111 and parametric spatial referencing systems) The ISO standards are still in flux; so long as we *engage* with ISO/TC 211 we can adapt the standards to suit WMO This profile is a *big* step forward, but it should not be considered a final version … it will continue to evolve

ISO 19118 Geographic Information - Encoding ISO 19118 Geographic information – Encoding specifies rules for encoding geographic information … i.e. converting from the UML model to XML schema ISO 19139 Clause 8 presents a good summary in relation to encoding the ISO 19115 information model

ISO 19139 – Encoding summary (1) Each UML class is encoded into 3 XML constructs: 1.XML Class Type (XCT) describing the content (attributes) of the UML class 2.XML Class Global Element (XCGE) ensuring the class has global visibility within the XML schema for import etc. 3.XML Class Property Type containment of a class is managed through the XML Class Property Type of its data type, enabling both by Value and by Ref implementations of content Note: when an XCT is of xs:simpleType, by Ref is not permitted

ISO 19139 – Encoding summary (2) Naming conventions: UML class » Class1 XCT » Class1_Type XCGE» Class1 XCPT» Class1_PropertyType Special case encodings: Abstract classes Inheritance and sub-classes Note: to achieve interoperability only extension sub-classing (i.e. adding attributes) is permitted – restriction and multiple inheritance are not allowed Enumerations Codelists Unions

Polymorphism and substitution groups (1) Polymorphism: the ability to assume different forms Example: [CI_ResponsibleParty] » individualName [CharacterString] could be specialized such that name is compartmentalized into first and last names Polymorphism provides communities with a mechanism to better refine metadata to meet organizational need individualName is extended within a community namespace … whilst still utilizing ISO 19139 schemas (gmd namespace), and still providing usable & understandable instance documents In OO, the specialized class is a type of the general class; e.g. a dog is a type of animal

Polymorphism and substitution groups (2) The is a relationship implies semantic consistency & substitutability ISO 19118 *only* permits simple (extension-only) sub- classing / specialization ISO 19139 allows polymorphism primarily though the _PropertyType encodings; e.g. gmd:PT_FreeText_PropertyType is substituted for the more general gco:CharacterString_PropertyType for multi-lingual support Need to inform the XML parser of the substitution: a)via a substitutionGroup directive in the schema, OR b)via a xsi:type directive in the instance document

GML pattern: by-value or by-reference (1) GML properties are defined such that the content can be referenced EITHER by-value within the scope of the containing XML element, OR by-ref (xlink) to an instance of the content residing elsewhere; either within the document or external

GML pattern: by-value or by-reference (2) Example - from an observations & measures GML instance 8903 … by-reference by-value

«xlink» semantics How should parsers interpret xlink? XML validation will *only* check the grammar of the xlink statement xlink has deferred binding semantics …

GML pattern: object-type-object-type striping object type object 8903 -30.7025065 134.1997256

Interoperability outside WMO community Document without WMO extensions Document with WMO extensions XSL Transformation Users outside WMO community will (probably) NOT understand WMO extensions … Need to remove them???

Open Issues Worked examples & implementation test-bed Finalize extensions which are required? Time, ServiceIdentification etc. encode as ISO 19118-compliant XML schema ISO 19115 / 19139 have a multitude of options for describing information … which makes writing parsing applications complex do we need to *restrict* WMO Core metadata? ISO/TC 211 & OGC community peer review

Thank you

Others: irregular point sets exists in WMO Metadata Profile v0.2 can be used to describe the geographic locations of a set of stations never needed if station catalogue files exists remove IrregularPointSet_Type from WMO Metadata Profile

© Crown copyright 2006 Times relevant to a observations … Observations and Measurements … From the Observations and Measurements metamodel (Simon Cox, CSIRO) … [OGC ref 05-087r3 & from the SEEGRid twiki]SEEGRid twiki An Observation is an Event whose Result is an Estimate of the Value of some Property

© Crown copyright 2006 Times relevant to a observations … Events … We assert that O&M provides a sound basis for meteorological observation features How does O&M capture times? … om:AbstractObservation extends om:Event om:Event content model is derived from gml:AbstractGMLType by adding the following properties: time - whose value is a TM_Object (i.e. TM_Primitive or TM_Complex) describing when the event occurred location - whose value is the Location of the event (if known) responsible - whose value indicates a party (Person, Organisation) responsible for the event precedingEvent and followingEvent optional pointers to other events in a sequence

© Crown copyright 2006 Times relevant to a observations … a single observation … eventTime (t e ) eventTime encoded in Observations & Measures as: … 2005-01-11T16:22:25.00 … eventTime encoded in Observations & Measures as: … 2005-01-11T16:22:25.00 … Time at which the observation event occurred (from om:Event) (Often referred to as validTime within GML schemas) issueTime (t i ) Time at which the observation was published / issued … allowing for amendments to a previously published observation (we need to extend O&M for this) real time axis (t) Time in the real world Default temporal reference system: ISO-8601 (Gregorian calendar) Observation

© Crown copyright 2006 Times relevant to a observations … what about accumulations? … eventTime (t e ) time interval Time interval relative to the observation time for calculating accumulations, averages etc. An instantaneous observation is conceptually simple; e.g. measuring temperature at a specific instant in time However, what about accumulations (or averages etc.) … e.g. measuring a 3-hr average temperature? We assert that you cant evaluate the average until the end of the 3-hr period. We assert that the time interval is a property of the measured phenomena (a 3-hr average) & the eventTime (t e ) of observation occurs at the end of the time interval. An instantaneous observation is conceptually simple; e.g. measuring temperature at a specific instant in time However, what about accumulations (or averages etc.) … e.g. measuring a 3-hr average temperature? We assert that you cant evaluate the average until the end of the 3-hr period. We assert that the time interval is a property of the measured phenomena (a 3-hr average) & the eventTime (t e ) of observation occurs at the end of the time interval. issueTime (t i ) real time axis (t)

© Crown copyright 2006 Times relevant to a observations … what about maxima & minima? … eventTime (t e ) time interval The primary observation (in this example) is the maximum temperature during a time interval. The maximum temperature cannot be evaluated until the end of the time interval. We assert that the time interval is a property of the measured phenomena (a daily maximum) & the eventTime (t e ) time of observation occurs at the end of the time interval. In many cases, the exact instance when the maximum temperature occurred cannot be determined. However, automated weather stations now offer near-continuous measurement & can record the time instant that an event (i.e. the maximum temperature) occurred. We assert that the maximum temperature event can be modelled as a related observation. The primary observation (in this example) is the maximum temperature during a time interval. The maximum temperature cannot be evaluated until the end of the time interval. We assert that the time interval is a property of the measured phenomena (a daily maximum) & the eventTime (t e ) time of observation occurs at the end of the time interval. In many cases, the exact instance when the maximum temperature occurred cannot be determined. However, automated weather stations now offer near-continuous measurement & can record the time instant that an event (i.e. the maximum temperature) occurred. We assert that the maximum temperature event can be modelled as a related observation. real time axis (t) x Temperature fluctuation during time interval Time instant at which the maximum temperature occurs during the time interval Related observation: temperature recorded at time instant Related observation: temperature recorded at time instant Primary observation: Maximum temperature recorded during time interval Primary observation: Maximum temperature recorded during time interval

© Crown copyright 2006 Times relevant to a observations … what about collections of obs? … eventTime ( t e ) collectionPeriod is the time interval bounding all discrete observations within the collection (note: this would probably be encoded as an element of the spatio-temporal bounding box for the collection) collectionPeriod is the time interval bounding all discrete observations within the collection (note: this would probably be encoded as an element of the spatio-temporal bounding box for the collection) collectionPeriod real time axis (t)

© Crown copyright 2006 Which time values are needed in observation feature types? eventTime (t e ) Time at which the observation event occurred time interval (for calculating accumulations, averages, max/min etc.) part of the phenomenon definition Not valid: collectionPeriod Time interval bounding all discrete observations within the collection (where appropriate) Time properties: issueTime (t i ) Time at which the observation was published … allowing for amendments

© Crown copyright 2006 Encoding eventTime in ISO 19115 & ISO 19139 For a single observation, or a collection of observations with a common eventTime (t e ) … metadata [MD_Metadata] » identificationInfo [MD_DataIdentification] » extent [EX_Extent] » temporalElement [EX_TemporalExtent] » extent [TM_Instant] For a single observation, or a collection of observations with a common eventTime (t e ) … metadata [MD_Metadata] » identificationInfo [MD_DataIdentification] » extent [EX_Extent] » temporalElement [EX_TemporalExtent] » extent [TM_Instant] 2005-01-11T16:22:25.00 2005-01-11T16:22:25.00

© Crown copyright 2006 Encoding collectionPeriod in ISO 19115 & ISO 19139 For a collection of observations spanning multiple times, collectionPeriod … metadata [MD_Metadata] » identificationInfo [MD_DataIdentification] » extent [EX_Extent] » temporalElement [EX_TemporalExtent] » extent [TM_Period] For a collection of observations spanning multiple times, collectionPeriod … metadata [MD_Metadata] » identificationInfo [MD_DataIdentification] » extent [EX_Extent] » temporalElement [EX_TemporalExtent] » extent [TM_Period] 2006-01-11T16:22:25.00 2006-01-12T16:22:25.00 2006-01-11T16:22:25.00 2006-01-12T16:22:25.00

© Crown copyright 2006 Encoding issueTime in ISO 19115 & ISO 19139 issueTime … metadata [MD_Metadata] » dateStamp [Date] metadata [MD_Metadata] » identificationInfo [MD_DataIdentification] » citation [CI_Citation] » date [CI_Date] » date [Date] dateType [CI_DateTypeCode] edition [CharacterString] {creation, publication, revision} editionDate [Date] Problem: date field only … in meteorology we need to differentiate on smaller time scales EITHER 1.extend metadata standard, OR 2.use edition information to capture metadata information for amends etc. issueTime … metadata [MD_Metadata] » dateStamp [Date] metadata [MD_Metadata] » identificationInfo [MD_DataIdentification] » citation [CI_Citation] » date [CI_Date] » date [Date] dateType [CI_DateTypeCode] edition [CharacterString] {creation, publication, revision} editionDate [Date] Problem: date field only … in meteorology we need to differentiate on smaller time scales EITHER 1.extend metadata standard, OR 2.use edition information to capture metadata information for amends etc. 2006-02-20 1993-01-01 creation 2006-02-20 1993-01-01 creation

© Crown copyright 2006 Indeterminate times in GML – ISO 19136 Inexact temporal positions may be expressed using the optional indeterminatePosition attribute. This takes a value from an enumeration defined as follows: These values are interpreted as follows: unknown indicates that no specific value for temporal position is provided. now indicates that the specified value shall be replaced with the current temporal position whenever the value is accessed. before indicates that the actual temporal position is unknown, but it is known to be before the specified value. after indicates that the actual temporal position is unknown, but it is known to be after the specified value.

© Crown copyright 2006 Times relevant to a simulation … time in the real world … creationTime (t c ) Time at which the simulation was executed issueTime (t i ) Time at results of the simulation were published / issued time axis (t) Time of an event that has been simulated … i.e. a simulated observation datumTime (t d ) The origin (datum) time used in the simulation eventTime (t e ) x

© Crown copyright 2006 Times relevant to a simulation … assimilation vs. prediction … time axis (t) datumTime (t d ) or analysisTime (t a ) initialisationTime (t 0 ) assimilation period Consider a forecast … the simulation is run to give a prediction from the datumTime (t d ) to some arbitrary time in the future however, the simulation begins earlier at the initialisationTime (t 0 )… allowing data to be assimilated into the simulation the analysis is produced at the end of the assimilation period the analysisTime (t a ) corresponds with the datumTime (t d ) Consider a forecast … the simulation is run to give a prediction from the datumTime (t d ) to some arbitrary time in the future however, the simulation begins earlier at the initialisationTime (t 0 )… allowing data to be assimilated into the simulation the analysis is produced at the end of the assimilation period the analysisTime (t a ) corresponds with the datumTime (t d ) eventTime (t e ) x

© Crown copyright 2006 Times relevant to a simulation … usage periods … time axis (t) datumTime (t d ) usageStartTime usageExpiryTime validUsagePeriod validUsagePeriod is the interval during which the results of the simulation should be used. Most often, simulation results do not have a valid usage period. However, we must include the concept as it is required for TAFs Whilst not obvious, the issueTime (t i ) and the start of the usage period do not need to coincide validUsagePeriod is the interval during which the results of the simulation should be used. Most often, simulation results do not have a valid usage period. However, we must include the concept as it is required for TAFs Whilst not obvious, the issueTime (t i ) and the start of the usage period do not need to coincide eventTime (t e ) validUsagePeriod may extend beyond the eventTime (t e ) x

© Crown copyright 2006 x A set of results from a simulation (a model run) time axis (t) datumTime (t d ) Collection of discrete simulation result-sets that share the same DatumTime eventTime (t e ) finalTime (t f ) End of the simulation … finalTime (t f ) collectionPeriod

© Crown copyright 2006 Times relevant to a simulation … the axes of time for simulations … real time axis (t) simulation time axis (T) datumTime (t d ) simulationDatumTime (T d ) simulationTime (T s ) Example: T+60 The origin time for the simulation; e.g. T+0 eventTime (t e ) simulation time (T) is projected onto real time (t) … although this is not always straightforward with 360-day calendars for climate models! simulation time (T) is projected onto real time (t) … although this is not always straightforward with 360-day calendars for climate models! Time in the real world Default temporal reference system: ISO-8601 (Gregorian calendar) Time in the real world Default temporal reference system: ISO-8601 (Gregorian calendar) Time in the conceptual world of the numerical simulation Temporal coordinate reference system defined locally for the simulation using Time in the conceptual world of the numerical simulation Temporal coordinate reference system defined locally for the simulation using

© Crown copyright 2006 Example encoding of a local temporal reference system Temporal coordinate reference system (hours since midnight UTC 9 th March 2006) encoded as: Number of hours since midnight UTC, 9 th March 2006 Simulation time axis global 2006-03-09T00:00:00.00 H Temporal coordinate reference system (hours since midnight UTC 9 th March 2006) encoded as: Number of hours since midnight UTC, 9 th March 2006 Simulation time axis global 2006-03-09T00:00:00.00 H Time instant T+60 (relating to local temporal reference system) encoded as: 60 Time instant T+60 (relating to local temporal reference system) encoded as: 60

© Crown copyright 2006 Which time values are needed in simulation metadata? (at least for operational meteorology!) datumTime (t d ) or analysisTime (t a ) eventTime (t e ) creationTime (t c ) issueTime (t i ) validUsagePeriod usageStartTime usageExpiryTime initialisationTime (t 0 ) finalTime (t f ) publication metadata primary metadata primary metadata simulation metadata simulation metadata collectionPeriod simulatedTime (T s )

© Crown copyright 2006 Encoding primary time metadata in ISO 19115 & ISO 19139 (1) Encode as for observations … except you *may* want to use two temporal extent definitions to describe time instants in both Gregorian and simulated reference frames Encode as for observations … except you *may* want to use two temporal extent definitions to describe time instants in both Gregorian and simulated reference frames eventTime (t e ) collectionPeriod simulatedTime (T s ) 2005-01-11T16:22:25.00 60 2005-01-11T16:22:25.00 60

© Crown copyright 2006 Encoding primary time metadata in ISO 19115 & ISO 19139 (2) eventTime (t e ) simulatedTime (T s ) Problem: 1.it *may* be difficult for parsers to differentiate between multiple temporal extents; e.g. when attempting to build an index on the content of the metadata record 2.there is no convenient placeholder for the local temporal reference system definition it *may* be necessary to extend the ISO 19115 metadata standard to allow alternate time extents to be specified, along with their local reference system definition use a similar pattern to expressing multi-lingual alternatives for character strings … Problem: 1.it *may* be difficult for parsers to differentiate between multiple temporal extents; e.g. when attempting to build an index on the content of the metadata record 2.there is no convenient placeholder for the local temporal reference system definition it *may* be necessary to extend the ISO 19115 metadata standard to allow alternate time extents to be specified, along with their local reference system definition use a similar pattern to expressing multi-lingual alternatives for character strings …

© Crown copyright 2006 2005-01-11T16:22:25.00 Number of hours since midnight UTC, 9th March 2006 Simulation time axis 2006-03-09T00:00:00.00 H 60 2005-01-11T16:22:25.00 Number of hours since midnight UTC, 9th March 2006 Simulation time axis 2006-03-09T00:00:00.00 H 60 Encoding primary time metadata in ISO 19115 & ISO 19139 (4) datumTime (t d ) simulationTime (T s ) eventTime (t e ) specify use of WMO extended temporal extent WMO_TemporalEXtent_PropertyType contains both EX_TemporalExtent and WMO_TemporalExtent

© Crown copyright 2006 Encoding publication time metadata in ISO 19115 & ISO 19139 Encode as for observations metadata [MD_Metadata] » identificationInfo [MD_DataIdentification] » citation [CI_Citation] » date [CI_Date] » date [Date] dateType [CI_DateTypeCode] edition [CharacterString] {creation, publication, revision} editionDate [Date] employing the CI_DateTypeCode to describe the type of the publication Encode as for observations metadata [MD_Metadata] » identificationInfo [MD_DataIdentification] » citation [CI_Citation] » date [CI_Date] » date [Date] dateType [CI_DateTypeCode] edition [CharacterString] {creation, publication, revision} editionDate [Date] employing the CI_DateTypeCode to describe the type of the publication creationTime (t c ) issueTime (t i ) validUsagePeriod usageStartTime usageExpiryTime Encode validUsagePeriod as 2006-01-11T16:22:25.00 2006-01-12T16:22:25.00 Encode validUsagePeriod as 2006-01-11T16:22:25.00 2006-01-12T16:22:25.00

© Crown copyright 2006 Temporal usage constraints – extension required to ISO 19115? ISO 19115 defines constraint information; the metadata required for managing rights to information including restrictions on access and use. The metadata entity seems the most appropriate placeholder for temporal usage constraints … however, ISO 19115 only details: MD_LegalConstraints MD_SecurityConstraints To record temporal usage constraints in the metadata record, we will need to extend ISO 19115; e.g. WMO_TemporalUsageConstraints Question: is this type of metadata required in WMO core?

© Crown copyright 2006 Encoding simulation time metadata in ISO 19115 & ISO 19139 These metadata elements are artefacts of the numerical simulation itself. Furthermore, there are potentially many more metadata elements which *may* prove useful to discriminate between datasets (e.g. ensembleID) The British Atmospheric Data Centre (BADC) are working on an ISO 19115 extension to define metadata about numerical simulations: http://proj.badc.rl.ac.uk/ndg/wiki/NumSim These metadata elements are artefacts of the numerical simulation itself. Furthermore, there are potentially many more metadata elements which *may* prove useful to discriminate between datasets (e.g. ensembleID) The British Atmospheric Data Centre (BADC) are working on an ISO 19115 extension to define metadata about numerical simulations: http://proj.badc.rl.ac.uk/ndg/wiki/NumSim datumTime (t d ) or analysisTime (t a ) … initialisationTime (t 0 ) finalTime (t f ) ensembleID

© Crown copyright 2006 NDG NumSim extension Numerical Simulation Discovery Metadata (aka NumSim) The DIF describes datasets at the discovery level, but where simulations are involved, discovery metadata needs more information than is available in existing schema. A new schema which is being trialled at the BADC should be accessible to both DIF and ISO19115 parent discovery schema, although at the moment it is rather standalone. … Proposal: WMO adopts NumSim as a formal mechanism for describing simulation metadata within WMO Core metadata profile. Prior to adoption, WMO should liaise with BADC to ensure the the profile is fit for purpose and has been rigorously tested.

Implementing codelists 3 rd May 2006 by Jeremy Tandy, UK Met Office Jürgen Seib, Deutscher Wetterdienst

Codelists A permissible extension of ISO 19115 is that free text content can be restricted by the use of a codelist Furthermore, existing codelists can be extended by adding more terms to the list Note that this is NOT possible with enumerations – an enumeration is NOT extensible An «Enumeration» is implemented as an XML schema enumeration list A «Codelist» is implemented as a codelist catalogue file WMO Core profile v0.2 identified a small number of *new* code lists

ISO/TS 19139:2005(E) – Clause 8.5.5 Codelist encodings (1) A class that is stereotyped CodeList is an enumerated type like a class that is stereotyped Enumeration. The difference is that the > class is extensible. All > classes defined in ISO 19115, Annex B, are described in tables with three columns: Name, DomainCode and Definition. Codelists and their associated definitions are controlled in a register. ISO 19115, Annex B contains the content of a register or registers that could be created that is well understood by software.

ISO/TS 19139:2005(E) – Clause 8.5.5 Codelist encodings (2) The last point is the crucial *implementation* issue … Values of a codelist are NOT encoded in the schema (as is the case for an enumeration) Codelist values are stored in some external register Issue: XML validation CANNOT verify codelist entries

Implementing code lists: alternative define all WMO code lists of type «enumeration» Issues: 1)Enumeration does not support multi-language 2)Codelists as enumerations is INFLEXIBLE … it does not permit extension (or local extension) … refer to complexity regarding BUFR 3)XML schema gives SYNTACTIC interoperability via XML schema validation … we need SEMANTIC interoperability via application-level parser

ISO 19139 Codelist schema Where codelists are referenced from within a metadata record, the following XML type is used: Example instance values: codeList = http://www.tc211.org/ISO19139/resources/codeList.xml#CI_DateTypeCode codeListValue="creation"

Codelist implementation example – CI_DateTypeCode (1) The XML global element corresponding to CI_DateTypeCode: <xs:element name="CI_DateTypeCode" type="gco:CodeListValue_Type" substitutionGroup="gco:CharacterString"/> The XML PropertyType corresponding to CI_DateTypeCode:

Codelist implementation example – CI_DateTypeCode (2) 1993-01-01 <CI_DateTypeCode codeList="./resources/codeList.xml#CI_DateTypeCode" codeListValue="publication">publication … implementation of codelist registers will be discussed later …

WMO metadata profile codelist extensions WMO Core profile v0.2 identified a small number of *new* code lists: WMO topic categories «enumeration» WMO keywords «thesaurus» WMO data frequency code «codelist» WMO member countries «codelist»

Code lists: WMO topic categories MD_TopicCategoryCode far too restrictive … Create new WMO specialisation: WMO_CommunityTopicCategoryCode (as proposed in WMO Core v0.2)

WMO topic categories - schema … …

Example: WMO topic categories...... climatologyMeteorologyAtmosphere <topicCategory xsi:type=wmo:WMO_CommunityTopicCategoryCode_PropertyType > weatherObservation....... (This part *may* not be required)

SIMDAT: metadata directory structure (1) SIMDAT (phase 1) employed WMO Core Metadata v0.2 was misused to hold a directory structure for the metadata instance … Example: NWP Outputs > ECMWF > 40 years reanalysis This implementation is NOT ISO 19115 compliant Proposal: Use MD_DataIdentification » supplementalInformation as a placeholder for the directory

SIMDAT: metadata directory structure (2) MD_DataIdentification::supplementalInformation «gco:CharacterString_PropertyType» Question: leave as free text or formalize with a metadata extension?

Code lists: WMO keywords enumeration list type WMO_KeywordCodeType exists in WMO Metadata Profile v0.2 <xs:attribute name="dictionary type="xs:anyURI use="optional"/> <xs:element name="WMO_keyword" type="wmo:WMO_KeywordType substitutionGroup="gco:CharacterString"/>

Example: WMO keywords...... temperature climate data.......

Code lists: WMO keywords MD_KeywordTypeCode … WMO Core v0.2 proposed a new WMO keyword list: WMO_KeywordList (a VERY long list!) WMO Core v0.2 expressed this as an enumeration … Also put the actual keyword list *content* into the keyword *type* list (?)

ISO 19139 keywords implementation keyword … free text field type … from «MD_KeywordTypeCode» codelist classifies the type of keyword does this codelist need extension? thesaurusName … «CI_Citation» identifies the thesaurus that describes the permissible content of the keyword list thesaurusName [CI_Citation] » identifier [MD_Identfier] » code [CharacterString] can be used to express the URI of the thesaurus / codelist … allowing linkage to URL or URN (alternative: substitute gmx:Anchor for gco:CharacterString to reference the thesaurus)

WMO keyword – thesaurus implementation Keyword thesaurus content (i.e. the list of keywords and their meanings) can be implemented as a)URN linkage to existing WMO code manuals urn:x-wmo:wmoManual:306:synop ??? (note: an application will need some additional, pre-defined context to dereference the URN) b)URL linkage to online catalogue; encoded according to the codelist catalogue pattern (see later)

Keyword examples climate data relative humidity theme … urn:x-wmo:wmoManual:306:synop … note: XML elements in GML can also be expressed by reference

Code lists: frequency values MD_MaintenanceFrequencyCode too restrictive … WMO Core v0.2 proposed an extended list: WMO_DataFrequencyCode expressed as an enumeration in WMO Core v0.2

WMO_DataFrequencyCode implementation Standard codelist implementation … Global XML element … <xs:element name=WMO_DataFrequencyCode" type="gco:CodeListValue_Type" substitutionGroup="gco:CharacterString"/> XML PropertyType …

WMO_DataFrequencyCode example … daily...

Frequency values – alternative implementation type WMO_DataFrequencyCodeType exists in WMO Metadata Profile v0.2 remove this enumeration type from the profile use xs:duration data type to specify frequency values A value of xs:duration is specified in the form " PnYnMnDTnHnMnS Examples: PT3H: period of 3 hours P5Y2M10D: period of 5 years, 2 months, and 10 days.

Code lists: WMO member countries The organisation responsible for various aspects of the metadata instance is defined thus: [CI_Citation] » citedResponsibleParty [CI_ResponsibleParty] » organisationName [CharacterString] WMO profile needs to formalise list of responsible organisations as the member countries of WMO WMO_WMO-MemberCountryCode

WMO_WMO-MemberCountryCode implementation Standard codelist implementation … Global XML element … <xs:element name=WMO_WMO-MemberCountryCode" type="gco:CodeListValue_Type" substitutionGroup="gco:CharacterString"/> XML PropertyType … <xs:complexType name=WMO_WMO-MemberCountryCode_PropertyType"> <xs:element ref=wmo:WMO_WMO-MemberCountryCode minOccurs=0/>

WMO_WMO-MemberCountryCode example … Deutscher Wetterdienst...

Member country list – alternative implementation does not exist in WMO Metadata Profile v0.2 should be implemented as an XML enumeration type....... <xs:element name="Country type="wmo:WMO_MemberCountriesCodeType substitutionGroup="gmd:Country"/>

Member country list – alternative implementation...... Germany.......

Thank you

Service metadata Encoding in ISO 19119 metadata May 2006

Service metadata WMO Core Profile key concern is describing *datasets* … Implication: MD_DataIdentification is sufficient? This is NOT the case … Where a dataset is described (i.e. via a WMO Core metadata record) you need to be able to identify the *service* by which you can *access* the data … Example: when a GISC harvests metadata records from a DCPC (refer to plans for CBS Workshop demonstration Nov 2006)

Service metadata in ISO 19115

ISO 19119:2005 Geographic information - Services Service metadata is described in ISO 19119 MD_ServiceIdentification is replaced with SV_ServiceIdentification The ISO standard discusses much more than simple *access* services … e.g. defining metadata constructs that can be used to describe service chaining Alternative service description standards (including WSDL) were deemed incomplete and insufficient

ISO 19119:2005 UML model (1)

ISO 19119:2005 UML model (2)

ISO 19119:2005 – implementation (1) ISO 19119 seems to meet requirements But … 1.there is no ISO-ratified encoding (equivalent to ISO 19139) although an incomplete (?) ISO 19118 compliant XML encoding exists from OGC CSW initiative 2.there does not appear to be a place holder to reference pre- existing WSDL definitions most implementation examples I have seen (OGC service offerings) have a WSDL definition in *parallel* to an ISO 19119 definition

ISO 19119:2005 – implementation (2) Best practice for WMO Core metadata? Bind the service definition to the dataset via the operatesOn relationship (via xlink reference) Set SV_CouplingType as mixed Alternative data access service binding? [MD_Distribution] » transferOptions [MD_DigitalTransferOptions] » onLine [CI_OnlineResource] Extend CI_OnlineResource to hold SV_ServiceIdentification, wsdl:definition & default values / predefined queries?

ISO 19119:2005 – implementation (3) Incorporating WSDL service definitions? Include *both* SV_ServiceIdentification and wsdl:definitions elements … … … … … … … …

Default parameters / parameter ranges SIMDAT (phase 1) implemented bespoke service binding constructs ISO 19119 provides alternative implementation … Except for a mechanism for identifying default (fixed) values & ranges of values Extend ISO standard information model to cater for default values or range lists? int.ecmwf.mars e4 sfc marser 2/2 1980-01-01 1990-12-31 0000 1200

Thank you

Catalogues and registries 3 rd May 2006 by Jeremy Tandy, UK Met Office Jürgen Seib, Deutscher Wetterdienst

Feature catalogues Current WMO Core best practice: dataset content identified via keywords Alternative: define content model as GML feature … a feature type UK Met Office undertaking to develop GML feature types for meteorological information (http://www.metoffice.gov.uk/informatics) Feature types are registered in a feature catalogue

Feature catalogue - implementation Best practice implementation for feature catalogues is in flux ISO standards: ISO 19110: Geographic information – Methodology for feature cataloguing (new work item) ISO 19126: Geographic information – Profiles for feature data dictionary registers and feature catalogue registers ISO 19135 Geographic Information – Procedures for registration of items of geographic information Open Geospatial Consortium initiatives: MOTIIVE; INSPIRE-related project aiming to develop best practice methodology for implementing feature catalogues within registries

Supporting metadata A key objective of IPET-MI is to define the schemas for WMO Core metadata … However, a number of resources are *external* to the metadata instances … Coordinate Reference System definitions Unit of Measure definitions Phenomena (parameter) definitions Codelists Keyword thesauri Feature catalogues Gazetteers Station lists

Registries and catalogues (1) These supporting metadata artefacts are registered in a *catalogue* or *registry* Definition: a registry is a catalogue with *governance* How do you implement a catalogue? Simple: create an XML instance document containing the registered definitions & reference the content via hyperlinks Issue: brittle implementation – relies on fixed URLs … susceptible to broken links

Registries and catalogues (2) Feature rich: import the content into a *repository* and use a sophisticated registry to index the definitions, abstracting the *real* location of the documents, enabling the expression of rich content models and the traversal of associations between resources Issue: complex implementation, limited reference implementations UK Met Office have undertaken to develop a registry- repository implementation based on OGC CSW and ebRIM 3.0; planned demonstration at CBS Workshop, Nov 2006

ISO 19139 catalogue implementation 3 concrete catalogue classes: 1.Coordinate Reference System 2.Unit of Measure 3.Codelist

ISO 19139 … codelist catalogue implementation Example: CT_CodelistCatalogue

Codelist catalogue – XML encoding Also a multi-lingual implementation available from ISO 19139

Codelist catalogue: example instance (1) (http://www.isotc211.org/2005/resources/gmxCodelists.xml) gmxCodelists Codelists for description of metadata datasets compliant with ISO/TC 211 19115:2003 and 19139 GMX (and imported) namespace 0.0 2005-03-18 … code list items …

Codelist catalogue: example instance (2) identification of when a given event occurred CI_DateTypeCode date identifies when the resource was brought into existence creation … more codeEntry elements …

Additional catalogues … CT_KeywordCatalogue CT_StationCatalogue CT_CentreCatalogue CT_ParameterCatalogue

Catalogues: keyword dictionary 1..* +multilingualKeyword CT_KeywordCataloguePT_FreeText

Catalogues: catalogue of centres 1..* +centre CT_CentreCatalogueMeteorologicalCentre +centreID: GenericName +name: CharacterString +shortName[0..1]: GenericName +contactInfo: CI_Contact

Volume A: observing stations hierarchy: WMO region country station name station index number latitude and longitude elevation in metres the elevation of the station (HP) the elevation of the ground (H) or the official altitude of the aerodrome (HA) pressure level in HPa observation times remarks

Catalogues: station catalogue CharacterString (from Text) GlobalStationId +code: IntStationCode LocalStationId +code: GenericName > IntStationCode +WMO +ICAO MeteorologicalCentre (from WMO namespace) +owner CT_StationCatalogue 1..* +station WMO_Station +stationName: CharacterString +country: CharacterString +wmoRegion: integer +latitude[0..1]: Decimal +longitude[0..1]: Decimal +elevationHP[0..1]: double +elevationH[0..1]: double +elevationHA[0..1]: double +pressureLevel[0..1]:integer +remarks[0..1]: CharacterString 0..* +stationId > StationId Product +productID: GenericName +timePerid[0..1]: TM_Period +accessRights[0..1]: MD_Constraints +quality[0..1]: DQ_DataQuality 0..* +product CI_Contact (from Metadata CI package) 0.. 1 +stationContact

Another UML model for stations 0..* +stationId > StationId WMO_Station +stationName: CharacterString +remarks[0..1]: CharacterString CI_Contact (from Metadata CI package) 0.. 1 +stationContact LandSurfaceStation +country: CharacterString +wmoRegion: integer +latitude[0..1]: Decimal +longitude[0..1]: Decimal +elevationHP[0..1]: double +elevationH[0..1]: double +elevationHA[0..1]: double +pressureLevel[0..1]:integer 0..* +product Product (from WMO namespace) Ship (from WMO namespace) Airplane (from WMO namespace) Buoys (from WMO namespace) RadiosondeStation (from WMO namespace)

Catalogues: station catalogue Use to reference a station Köln-Bonn

Catalogues: parameter catalogue 1..* +parameter CT_ParameterCatalogue MeteorologicalParameter +name: CharacterString +shortName[0..1]: GenericName +frequency: duration 1 +element MeteorologicalElement +name: CharacterString +shortName[0..1]: GenericName +unitOfMeasure: Unit Aggregation +function: AggregationCode +interval: duration 0..1 +subAggregation 0..1 +aggregation > AggregationCode +minimum +maximum +mean +average +sum Also see NASAs SWEET ontology, and Observations & Measure phenomena dictionary

Example: meteorological parameter monthly mean of daily minimum of 10 minutes air temperature observations PT10M air temperature degree C mean P1M minimum P1D

ISO 19112:2003 - Geographic information Spatial referencing by geographic identifiers

Gazetteer implementation – OGC 05-035 (1) Within the OGC community there is a growing interest in the development of a common feature- based model for access to named features, often referred to as a gazetteer. OGC 05-035 aims to implement a Gazetteer Service as a profile of the OGC Web Feature Service Gazetteer Service is a specialized profile of a Web Feature Service that specifies a minimum set of FeatureTypes and operations required to support an instance of a gazetteer service

Gazetteer implementation – OGC 05-035 (2) By using the capabilities of a Web Feature Server, the Gazetteer Service as proposed here exposes the following interfaces to query location instances in a gazetteer database: Get or Query features based on thesaurus- specific properties (broader term (BT), narrower term (NT), related term (RT) Retrieve properties of the gazetteer database, such as the location type class definitions and the spatial reference system definitions

Gazetteer implementation – interim The Gazetteer Service (WFS-G) initiative has developed a set of ISO 19118-compliant XML encodings for the ISO 19112 information model: SI_Gazetteer «FeatureType» SI_LocationInstance «FeatureType» SI_LocationType «FeatureType» … Recommendation: liaise with OGC regarding development of WFS-G Interim: use the ISO 19112 schema definitions to create a XML instance document for the gazetteer definitions & reference these via xlink from metadata instances Simple implementation Poor functionality (serving ONLY as a list)

Thank you

Page 1 A Proposal for a Reference Implementation of the WMO Core Metadata Profile based on ISO-19115/19139 3 rd May 2006 by Jeremy Tandy, UK Met Office.

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Page 1 A Proposal for a Reference Implementation of the WMO Core Metadata Profile based on ISO-19115/19139 3 rd May 2006 by Jeremy Tandy, UK Met Office.

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Presentation on theme: "Page 1 A Proposal for a Reference Implementation of the WMO Core Metadata Profile based on ISO-19115/19139 3 rd May 2006 by Jeremy Tandy, UK Met Office."— Presentation transcript:

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