CONCEPT DEFINITION TASK GROUP

Rome, Aug. 30, 2010

Agenda

Current status of vocabularies Reorganization of CGI workgroups Vocabulary resource management Change URI scheme from URN to http URI

Current GeoSciML

Vocabularies

(33 total)

Subversion repository

Current GeoSciML vocabs

Metadata

Preferred label(en, others)

Text definition (en)

Asserted hierarchy

Services

Auscope BRGM

Reorganization

New vocab group being organized Merge with Multilingual thesaurus group Develop statement of work Meeting planned this fall to formally

organize/kick off

Management

Move to repository to GeoSciML.org Authorities for OGE vocabularies (CGI

or ?)

New vocabulary requirements for v3 documents

Formal decisions and policies to be developed by new workgroup

URI SCHEMEFor CGI resources

http URIs

Identify information and non-information resources

expected to be dereferenceable using the existing DNS system on the Internet

Reasons for selecting HTTP URI

HTTP URI's are URI's, so may appear as the value of an @xlink:href in a GML-conformant document

They are persistent May identify offline- as well as online-resources Implies immediate resolvability -- a Good Thing in most

circumstances Structure is "facetted".

Enables more flexible rules for identifier governance. Composed of slash-delimited alphanumeric fields.

Allows some explicit semantics to be visible may imply resource-type, ownership, even value often useful during system development.

OGC has adopted in its service architecture (with apologies to Simon Cox https://www.seegrid.csiro.au/twiki/bin/view/CGIModel/CGIIdentifierScheme#URN_vs_URI)

What is identified

four distinct but related resources that we might like to identify using an HTTP URI (Booth) Identifier label: actual string (info) A concept or physical entity (non info) Web Location: the information resource that is

produced by an HTTP GET request using that URI (non information). There is no guarantee that the same web location will GET the same resource when it is recalled

A particular document instance (info)

URI requirements

Identifiable and transparent to people. Branding: trust, advertising; evident what is identified

Memorable Keyboard compatible Usable, reliable, documented Distributed (delegate support for the transfer of naming

authority)

Stable, cost effective Portable-- change dereferencing host system

without reengineering identifiers

Redirect

303 code response redirect is invisible to a human user

Compilicates relocation of the dereferencing host for legacy URIs.

Suggestion is to explicitly distinguish the dereferencing host from the name authority, these may be decoupled.

Content negotiation and URL redirection invisible to the user violate requirement for URI transparency

CGI URN scheme

“urn” “:” “cgi” “:” CGIResource “:” ResourceSpecificStri

ng

protocol Name authority Resource type Resource ID

CGI http URI scheme

“http” “://” host “/” “cgi-uri” “/” Authority “/” cgi resource “/” resource specific

identifier

Protocol Host authority URI scheme ID Name authority Resource type Resource ID

USGIN Scheme

"http:" "//" Host “/” URIscheme “/” nameAuthority “/” resourcePath “/” resourceSpecificString

“/” [representationPart]

protocol Dereferencing service URI scheme ID Name Authority ID Resource type Resoure ID Representation ID Representation

instance ID?

Examples from the wild

Stem part with host name, authority, resource type path part, opaque resource-specific part.

E.g. http://vocab.ndg.nerc.ac.uk/term/C161/0/28Bhhttp://www.eionet.europa.eu/gemet/concept/

7769http://zbw.eu/stw/descriptor/12880-5

Issues

Proposal to reverse the CGIResource/Authority pair to Authority/CGIResource

How are particular representations identified? file extensions ('.rdf', '.html'). content negotiation

Is host part considered part of the identifier string.

Underscores ‘_’ or hyphens ‘-’ in http URIs All characters

lower-case CamelCase

What is default representation

Rdf Html GeoSciML fragment Defined based on resource type