EuroGeographics Workshop Network Service, Paris, 2008-02-05/06 Download services Olaf Østensen Network Services Drafting Team

EuroGeographics Workshop Network Service, Paris, 2008-02-05/06

Download services

Olaf ØstensenNetwork Services Drafting

Team


Article 11

1. Member States shall establish and operate a network of the following services for the spatial data sets and services for which metadata have been created in accordance with this Directive:

(a) …(c) download services, enabling copies of spatial data sets, or parts of

such sets, to be downloaded and, where practicable, accessed directly;

(d) …

Directive text


Article 5

1. Member States shall ensure that metadata are created for the spatial data sets and services corresponding to the themes listed in Annexes I, II and III, and that those metadata are kept up to date.

…

Directive textArticle 11

1. Member States shall establish and operate a network of the following services for the spatial data sets and services for which metadata have been created in accordance with this Directive:

(a) …(c) download services, enabling copies of spatial data sets, or parts of

such sets, to be downloaded and, where practicable, accessed directly;

(d) … What does ”where

practicable” mean?


2) “spatial data” means any data with a direct or indirect reference to a specific location or geographical area;

3) “spatial data set” means an identifiable collection of spatial data;

4) “spatial data services” means the operations which may be performed, by invoking a computer application, on the spatial data contained in spatial data sets or on the related metadata;

Definitions


Definitions

• Dataset– one or more physical files serialized

in an encoding format– database realized in a concrete

database system– part of one of the above specified by

some filter (query, … )


Modelling principle - MDA

Model Driven Architecture


Simplified picture

Member state data

Harmonised MS data – real or ’virtual’

Download

FileFile

w/filterWFS

WCS

Harmonised GML schemas


Important background documents

• D2.5 DT DS Generic Conceptual Model

• D2.6 DT DS Methodology for the development of data specifications

• D2.7 DT DS Guidelines for the encoding of spatial data


New requirements from D2.7 - i)1 Rules for the encoding of updates

This clause can only be added in detail once

- DT NS has provided a draft for the download service – the general requirement is that a download services shall be able to provide updates;

- the requirements from the application use cases have been captured.

The current version contains the current understanding mostly based on the evaluation of reference material that needs to be confirmed / revised accordingly.

It is expected that the requirements below are not detailed enough, e.g. for cases where parts of the data is encoded in separate files (e.g. ranges of coverage functions).

Requirement 1 For all spatial object types for which updates shall be supported, a nilable property with name "changedInDataset" of type DateTime shall be defined in the application schema. The value shall be set in each spatial object. Spatial data sets which do not support this information shall set the value to nil. NOTE This requirement should be moved into the Generic Conceptual Model. As a result, changed spatial objects or versions could be queried from a download service by using that property in a query predicate.

The download service must support such queries.

NB! Numbering is wrong – due to copying


New requirements from D2.7 - ii)

For spatial object types which support change-only updates, the download service has to support additional capabilities. Requirement 1 Change-only updates of data shall be encoded using the <wfs:Transaction> message specified by ISO 19142 (Web Feature Service).

The download service must support additional operations (alternative, functionally equivalent options are possible, too):

- request for a change-only update for a dataset in a time interval, result is a <wfs:Transaction> message (pull);

- configuration of a download service so that changes to data results in a change-only update transmitted to a third party.

The need for these operations must be reconfirmed by requirements from the applications consuming INSPIRE data. If insufficient requirements are identified, Feil! Fant ikke referansekilden. should be removed again.



New requirements from D2.7 - iii)

1 Rules for exchange metadata Requirement 1 For data transfer using the transfer model (download of a complete spatial data set), the data set shall include the data set metadata for evaluation (as specified in the INSPIRE data specification) and use (the INSPIRE data specification itself). Requirement 2 For data transfer using the interoperability model (download of a spatial objects based on a query), the response of the download service shall not include any data set metadata, but shall provide a reference to the data set or data set series metadata in the discovery and registry services.



Generic use caseWorkflow

• Discover using a discovery service on metadata

• Select desired dataset(s)• Apply filter – F – for identifying part

of selected datasets (if appropriate)• Download using one or more

download services defined by the implementing rule


Metadata catalogueMetadata catalogue

DiscoverDiscover

ArchivesArchivesRepositoriesRepositories

discovery servicediscovery service

SelectSelect

Filter, queryFilter, query

DownloadDownload

filter ‘service’filter ‘service’

download service

download service

selection process – not specifiedselection process – not specified

networknetwork


Tools

• discovery service - DT-NS• harmonized

application schemas - DT-DS• filter encoding - OGC/ISO• web feature service - OGC/ISO• GML - OGC/ISO• web coverage service - OGC• ftp- and http-protocol - IETF• web services - W3C


More precise …Document Reference

1 RFC 2616 Hypertext Transfer Protocol -- HTTP/1.1

2 RFC 2818 HTTP Over TLS

3 RFC 959 File Transfer Protocol

4 ISO/CD 19142, Geographic information - Web Feature Service (also ISO/TC 211 N2128) current joint draft between OGC and ISO/TC 211 under ballot to become DIS by March 4, 2007

5 ISO/CD 19143, Geographic information - Filter encoding (also ISO/TC 211 N2143)current joint draft between OGC and ISO/TC 211 under ballot to become DIS by April 10, 2007

6 OpenGIS® Implementation Specification - Web Coverage Service (WCS) ImplementationSpecification Version: 1.1.0


Download Implementing Rule 1

• Full dataset download based upon discovery– normally implemented through a

discovery client– find, select, download using http– need to find out exactly what needs to

be specified and how• Variant: direct ftp or http on a

directory of a repository (?)


IR 1 – Full dataset download


Encoding – only GML?

It is required that the server provide the relevant MIME-type, e.g. in the case of a GML 3.2.1 dataset, MIME type text/xml; subtype=gml/3.2.1,

Discussion: Should dataset formats be restricted to an INSPIRE basket of different formats. I guess this is in the hands of DT-DS?

This implementing rule is very naïve in a way, but I am unsure to what extent we need to go into technicalities for this type of service that we all do every day, and which is intrinsically built into our computing environments.



• Partial dataset download based upon discovery and filter

• As the previous but with addition of a filter condition using FE– reliant upon FE and harmonized

application schema– do we need a simplified FE (profile), e.g.

independent of harmonized application schema

– do we need this rule at all?


IR 2 – Partial file download



• Partial (extreme case: full) download based upon WFS including FE– FE specification input based on

harmonized application schema– GML output according to harmonized

application schema– profiling based on

• CRSes• ??


Nota Bene

• Web Feature Service is under development in a joint OGC – ISO/TC 211 effort, leading to ISO 19142 – parallell voting in CEN

• Similar for Filter Encoding, leading to ISO 19143

• ISO 19142 and ISO 19143 will with almost certainty become ENs – i.e. European standards

• It is currently under consideration which versions the IR will be based upon


Proposal: IR require only basic WFS – probably not sufficient due to new requirements from D2.7

It shall be required that the server supports – and reports in the getCapabilities – the same set of SRS that is required for the View service. It is thus required that the server can transform to these SRS’es on the fly.

IR basisIR basis


New version ?

BasicWFS Transactional WFS

GetCapabilities Yes Yes

DescribeFeatureType Yes Yes

GetPropertyValue Yes Yes

GetFeature Yes Yes

Transaction No Yes

LockFeature No Yes

GetFeatureWithLock No Yes

IR basis



• Partial (extreme case: full) download based upon WCS including FE– FE specification input based on

harmonized application schema– GML output according to harmonized

application schema– profiling based on

• CRSes


To SOAP or not to SOAP …

• SOAP is not relevant forfile download

• ISO/CD 19142 (latest revision) contains a fragmentary description of SOAP binding in an informative annex(the same applies for WFS 1.1.0 clause 6.7)

• SOAP and GML – a problem?

• So … ??


Next steps in the Work Programme

Deliverables

DescriptionMilesto

neWho

NS - D 3.7Discovery and View

services

SDIC/LMO Consultation2007 –

12DT

Final Draft IR2008 –

03CT

Adoption of IR2008 –

05Comitolo

gy

NS - D 3.9 Download services

SDIC/LMO Consultation2008 – 03

DT

Final Draft IR2008 – 07

CT

Adoption of IR2008 – 11

Comitology

NS - D 3.10

Coordinates Transformation Services

SDIC/LMO Consultation2008 – 03

DT

Final Draft IR2008 – 07

CT

Adoption of IR2008 – 11

Comitology

Documents

EuroGeographics Workshop Network Service, Paris, 2008-02-05/06 Download services Olaf Østensen Network Services Drafting Team