Re: Semantic Web archaeology

Thanks a million, Dan! I think this answers the question and closes the 


Le 02/07/2019 à 16:27, Dan Brickley a écrit :
> On Fri, 28 Jun 2019 at 09:01, Antoine Zimmermann 
> < <>> wrote:
>     Recently on Stack Overflow, there was a question asking "Why rdf:Seq
>     and
>     not rdfs:Seq?" [1]. I tried to answer the best I could, by digging in
>     the old RDF mailing lists, but I am still puzzled about how some terms
>     ended up in the rdf: namespace rather than rdfs: (and vice versa). Can
>     someone involved in the early days of RDF enlighten us about this?
>     Nowadays, the duplication of namespaces for RDF terms seems rather
>     silly, confusing, and counter productive. Maybe it made sense, back in
>     the days...
> Sure, let me fill in some details, possibly too many. This all dates 
> from 1997. In 1997, several things happened.
> * W3C via its Metadata Activity ( led by 
> Ralph Swick, was getting reorganized. The PICS system for content 
> labelling was to be generalized. PICS already (from 1995/6) included a 
> label syntax (, signed labels 
> (, a rule language 
> ( and a "label 
> bureau" protocol. However it did not provide a way for multiple 
> independent labelling schemes to be used together, for rich structured 
> descriptions, and for datatyped (strings, numbers etc.) rather than 
> categorical rating values.
> * June 1997 - Netscape submitted Meta Content Framework (MCF) in XML,
> - both a spec 
> ( and a tutorial 
> (  While MCF is 
> clearly the technical ancestor to a lot of what you see in RDF, it 
> didn't have the same partitioning; the MCF spec had model, syntax, 
> schema and some starter vocabulary.
> * The Dublin Core metadata initiative, meanwhile, was trying to express 
> in-page Web metadata using HTML 3.2's simple "meta" tags, and 
> encountering difficulties with nested or repeated fields; e.g. see 
> (1996) 
> . This 1996 AHDS 
> report gives a feel for the metadata formats of that era, 
> . 
> For example, if you had multiple authors with multiple sets of contact 
> details each, you ended up with metadata fields named things like 
> "". See also for 
> Dublin Core community exploration of using MCF.
> * Lots of projects were crawling the Web and extracting metadata, e.g. 
> see the earlier 1996 workshop, 
> and 
> - you'd see mentions 
> of formats like SOIF from the Harvest indexing project, or MARC and the 
> Z39.50 protocol from libraries.
> * XML itself was taking shape (as a cut down format derrived from SGML), 
> including a draft namespaces mechanism.
> It was also the height of the browser wars.
> I'm sure I've missed a bunch of stuff, but the picture is basically that 
> the Web had just broken through into everyday life and things were crazy 
> and moving fast. So when W3C (itself a very new organization) planned 
> the RDF work there was a sense that it needed to be partitioned and 
> layered, and to get something useful out soon without being stuck in 
> complexity.
> Two RDF Working Groups were initially created in 1997; first (May 1997) 
> the Model and Syntax WG (pages are 
> W3C Members only, still), and a little later that year, the RDF Schema 
> WG
> Their charters are not public but I think it is reasonable to excerpt here.
>  From
> """Purpose and Scope: The Resource Description Framework Model and 
> Syntax Working Group (RDF-syntax-wg) will define an interchange format 
> for encoding and exchange of structured resource description data 
> (metadata) for Web resources. This framework will include all the 
> capabilities of PICS-1.1 and in addition will support more general 
> models of resource description, including non-numeric and structured 
> attribute values. The RDF Model and Syntax WG will work closely with an 
> RDF Schema WG.
> Requirements
> The goal of RDF is to provide a single mechanism for representing 
> metadata across many applications. The semantics and structure of many 
> varieties of metadata will be specified by independent communities. The 
> RDF must provide an infrastructure that is sufficiently general and 
> flexible to support these disparate applications. Example applications 
> include sitemaps, content ratings, stream channel definitions, search 
> engine data collection (web crawling), digital library collections, and 
> distributed authoring.
> Dependencies
> The RDF is an evolutionary step from PICS-1.1. The importance of the 
> content rating application is recognized explicitly by a requirement 
> that the RDF support existing PICS-1.1 data types and functional 
> specifications. It must be possible to automatically translate PICS-1.1 
> labels to RDF.
> The RDF Model and Syntax Working Group is responsible for defining an 
> architecture and interchange format for resource descriptions. The RDF 
> Schema design is the responsibility of a separate but closely 
> coordinated working group.
> There has been an agreement that the RDF work will build on top of XML, 
> and that the XML namespace work will supply some of the modularity 
> requirements for RDF.
> The Model and Syntax Working Group will also incorporate into the 
> Resource Description Framework any requirements for the purposes of 
> digitally signing resource descriptions defined by the W3C Digital 
> Signature Working Group."""
> The RDF Schema WG's charter followed along a few months later,
> """Purpose and Scope
> The Resource Description Framework Schema Working Group (RDF-schema-wg) 
> will define a model for schemas to specify the semantics of information 
> encoded in the Resource Description Framework and a language for the 
> encoding and exchange of those schemas.
> Requirements
> This schema model must be consistent with the data model produced by the 
> RDF Model and Syntax Working Group. While it is recognized that not all 
> aspects of metadata semantics can be described in a machine 
> understandable form the goal of the RDF Schema working group is to build 
> on well understood methods from the fields of database schema 
> representation and AI knowledge representation to enable this as far as 
> possible.
> The RDF Schema language must be syntactically compatible with the 
> language chosen by the RDF Model and Syntax Working Group and must 
> support all the functions in a PICS-1.1 rating service description. It 
> must be possible to automatically translate PICS-1.1 rating service 
> descriptions to RDF schemas.
> The goal of RDF is to provide a single mechanism for representing 
> metadata across many applications. The semantics and structure of many 
> varieties of metadata will be specified by independent communities. Much 
> of these semantics can be specified in a declarative machine 
> understandable form. Having such specifications available will greatly 
> improve interoperability. The goal of the RDF Schema mechanism is to 
> enable this.
> Dependencies
> The RDF Schema Working Group will coordinate with the RDF Model and 
> Syntax Working Group to insure that all the features of the data model 
> defined by the Model and Syntax Working Group are represented in the RDF 
> Schema specification.  The Metadata Coordination group will help with 
> this coordination."""
> ---
> In the two Working Groups, the way this played out was that the RDF M+S 
> WG introduced certain notions informally and "in passing", without 
> elaboration, and the RDFS group fleshed out some of those details. 
> Meanwhile, the RDFS WG took care not to introduce new syntax, and 
> decided to express its schema language within RDF using whatever syntax 
> the other Working Group created. The first public draft of RDF was the 
> M+S spec from October 1997:
> It already talked in MCF-like terms of "In this data model both the 
> resources being described and the values describing them are nodes in a 
> directed labeled graph (and values may also be resources). The arcs 
> connecting pairs of nodes correspond to the names of the property 
> types." ... and a basic notion of types followed along soon enough too. 
> The requirement to represent ordered structures within this otherwise 
> unordered graph data model was identified immediately, and tied in to 
> the practical requirements that came from PICS and from the various 
> other metadata efforts of that era that I've sketched.
> The RDF M+S WG put things in their namespace like rdf:type, while trying 
> to say as little as possible about the nature of namespaces, schemas and 
> related things. There was also a rough suggestion, sometimes articulated 
> explicitly, that multiple different schema systems could be built on top 
> of the base RDF. Or that instance data could stand alone, schema-less, 
> and still be useful. When DARPA's DAML came along a few years later, the 
> idea of alternatives to RDFS sharing the same base took more explicit 
> shape with DAML+OIL and OWL, but there were also some rather tense 
> discussions with XML groups in the 1997-9 period. XML was grounded in 
> SGML heritage and there was a broad expectation that the DTD part of 
> SGML (and XML) would eventually replaced/modernized, and that when this 
> happened, there would be an opportunity for the relationship between RDF 
> and XML to be made more explicit. XML people were not super happy at the 
> prospect of their future schema language being expressed somehow in RDF 
> (although Tim Bray made a draft exploring this, see 
> And the RDF/S WGs didn't see a way for 
> DTDs to really make sense for use with RDF. Nevertheless there were 
> clear points of overlap, e.g. datatypes. It was clear that 1998-era RDFS 
> wouldn't be the last word on the topic.  You can see some of this 
> baggage in earlier drafts of RDFS e.g. 
> as well as in 
> the later and 
> documents.
> The result of all this was pressure for RDFS to be a pretty minimalistic 
> language, one potentially replaceable, or elaborated upon later. This 
> also meant that there was a concern not to have too much RDFS leak into 
> the (hopefully uncontroversial) core of RDF, which needed to be 
> finalized and usable ASAP. That is roughly how we end up with things 
> like the "type" and "property" terminology being introduced in the RDF 
> M+S spec (and rdf: namespace), while structures making these ideas more 
> explicit (Class, Property etc.) were elaborated upon in "rdfs:" a little 
> later. As it happened, the M+S specification did make it to W3C REC 
> status in '99) whereas RDFS got stuck in limbo for a good while 
> afterwards, and only came back to formal life once W3C re-chartered the 
> Metadata Activity as the follow-on "Semantic Web" Activity in 2001. 
> has some bits and pieces from 
> that transition period.
> Nobody really liked rdf:Seq but it showed that order could be 
> represented in the graph structure, and the promise of "you could add a 
> utility vocabulary to express order differently" probably helped make it 
> bearable.
> </1990s>,
> Dan

Antoine Zimmermann
Institut Henri Fayol
École des Mines de Saint-Étienne
158 cours Fauriel
CS 62362
42023 Saint-Étienne Cedex 2
Tél:+33(0)4 77 42 66 03
Fax:+33(0)4 77 42 66 66
Member of team Connected Intelligence, Laboratoire Hubert Curien

Received on Friday, 5 July 2019 10:04:52 UTC