On Resources, Information Resources and Documents

It is crucial to understand the relationships of how the Web tries to describe and represent, or model, the world it is a part of. This is especially critical, since the most recent step of the evolution of the Web as Semantic Web is being realized. It shall enable machines to try to “understand” knowledge representations. Therefore, the terms Resource, Information Resource and Document are defined and their relationships are described in this article (see the illustrating graphic below). They are especially important to understand knowledge representation as it is also propagated in the Web.
This note is an attempt to explain my point of view regarding distinguishing the terms . At the beginning, I would like to define these terms. On this grounding, I would like to explain their relationships afterwards.


A Resource can be anything, i.e., a Resource is an entity regarding metaphysical terms. So, a Resource can be both a universal and a particular. It can be abstract or concrete – a concept, a categorization or a type (, a kind, a property or a relation), or an exemplification, an instantiation or a concrete object (cf. [1]). Following this differentiation, abstract objects are exemplified by concrete objects, and instantiations are categorized by concepts. Additionally, some particulars can be treated as universals for other particulars and recursively.
In terms of the Semantic Web, a Resource can be typed as rdfs:Resource, i.e., it can be characterized by a Description that is related to this CURIE (Compact URI). One can use a URI to denote a Resource, e.g., to name it in the Web. It is utilized for identification purpose in that context. So, a URI can be applied to identify a Resource1 in some way (cf. the synonyms of identify in [11]). One can call such a URI Resource URI.

Information Resources

Before I continue the definition of the issued terms of this note, I have to define a further term, which will be used by other concept specifications. This term is called Semantic Graph. It is a formal knowledge representation (a specific kind of Description) for concepts, particulars and their relations. On the one side, an ontology can be represented by a Semantic Graph, e.g., a Semantic Web ontology. On the other side, instantiations of universals of ontologies can be represented by a Semantic Graph, e.g., a Named Graph, too.
An Information Resource is a piece of information that describes (or represents) a Resource. It includes this amount of information that is necessary to describe a Resource in a certain kind. Hence, the Subject2 of an Information Resource is this characterized Resource. In general, an (abstract) Information Resource is usually realized by a Semantic Graph, which consists of a (concrete) Description of a Resource. This is necessary to make an Information Resource easily machine-processable. Of course, plain text is (more or less) easily processable by a human being, but not by a machine.
An Information Resource represents a Resource in some way. Nevertheless, it can not really represent a Resource completely. This is simply grounded in the nature of things that we can not really define what a complete Description shall be about. There exist at least always subjective Descriptions, which are unforeseeable.
In Semantic Web terms a Semantic Graph at least consists of one triple of the form: subject, predicate, object, however, often by a couple of triples. Such a triple is also called statement. To be more concrete, an Information Resource can be

It depends on the definition one specifies for “the amount of information that is necessary to describe a Resource in a certain kind” (see above). An example of such a definition is the following set:

  • statements that have the Resource URI as object + dereferencing the subject + predicate URI of that statement for human-readable titles or names
  • + statements that have the Resource URI as subject + dereferencing the object + predicate URI of that statement for human-readable titles or names
  • + (optionally) include all information of the statements of these object Resources recursively, if they are part of this Semantic Graph, i.e., include at least all blank node objects3

A Resource can have multiple Information Resources. Each of them is embodied as a Representation4 that is delivered by dereferencing a Resource URI (cf. first definition of embody in [12]). That is why, a Resource can have multiple Resource URIs. Every Resource URI belongs to one Information Resource5. Due to that reason, a Resource URI can be an alias for another Resource URI, because there can exist different Descriptions (Information Resources) of one and the same Resource.


A Document can be used to deliver an Information Resource to an Information Consumer (as a specific Information Service6). Therefore, it should include a Semantic Graph, which consists at least of a Semantic Graph of that Information Resource. In other words, a Document contains at least one Information Resource. However, a Semantic Graph of a Document can include further information – in Semantic Web terms further (RDF) statements. Thus, a Document is that envelope that is sometimes be needed to represent or deliver an Information Resource to an Information Consumer.
It is a concrete thing, a particular. A Document is a specific Representation, e.g., a computer document. Such a sequence of bits at least has a content type, for instance application/xhtml+rdfa, and a name, such as a Document URI, for example, http://example.com/test.html.
Albeit, some Information Consumers do not need this Document envelope. They can process, e.g., a Semantic Graph of an Information Resource without further information. Such Information Consumers simply get a serialized version of the Information Resource of a requested Resource URI in an appropriated Representation format, e.g., Notation 3.

Resource Description Level Representations

An overall expectation of an Information Consumer is that an Information Provider (as a specific Information Service6) should deliver an Information Resource as response to a requested Resource. To transfer this statement to the Semantic Web one can say:

“The Web of Things is built on top of a Web of (Realizations of) Information Resources (that are delivered by Information Services)” (cf. [5]).

Following this definition, an Information Resource can have multiple Representations that at least embody a Semantic Graph of that Information Resource. A Resource URI and a Document URI can be the same, if a Resource is a Document. However, the relationships of the resource description levels can be different in this context. Dereferencing that Resource URI can deliver the Information Resource that describes this Document

  1. in a computer document that has the Document URI as a name (a self description).
  2. in another computer document that has another Document URI as a name.
  3. in another Representation format.

All in all, at any time we should not directly infer knowledge about a Resource from Resource URIs, but always from Semantic Graphs (cf. Section 2.5 in [14]). For this interpretation task we ought to utilize especially those concrete Descriptions of the related Information Resources. These abstract Descriptions are addressed by the Resource URIs of a Resource. In that context, Resource URIs are simply present for dereferencing their Information Resources. Good URI design may sometimes help an Information Consumer to find a requested Information Resource. However, these interpretations are always expectations and are not fundamentally definitive.
The graphic below illustrates the relationships of the described terms.

Resource, Information Resource and Document - as graph with relations

Finally, one can say that everything can have an Information Resource (at least one).

Is a “real” thing, e.g., a car or a tree, itself “only” a Representation and hence a self description (Information Resource) of it? – If this is the case, then we can also claim, by insisting in Representationalism, that everything (every Resource) is an Information Resource.
For example, a human brain dereferences a Resource to an Information Resource in this context. In other words, one can simply identify a Resource by its Description (, which consists, e.g., of a (maybe quite difficult to imagine) Semantic Graph that connects and references other Resources). For me, this is an activity we are doing all the time. Thereby, some Resources occur by our understanding as “real” things.
Due to that conclusion, I guess, that I follow, from my understanding of Aristotle’s view, more then ever since before the Aristotelian realism. I can now conclude that every human being is a particular and a universal in its own, because one is both a self description and a self exemplification. Furthermore, one can insist the birth of a human being as an exemplification of/an attempt to exemplify the universals of the parents7. Ambiguousness exist, because we simply have at a specific temporal and spatial point only a partial understanding of things we perceive8. In that context, we cannot further reason to get the essence of a thing. So, it is a natural sensation, which is not bad at all. It is even often very helpful. However, it does not prevent us to reach a level of unambiguousness, which is not always necessary (cf. [15]).

(Tim Berners-Lee has a definition of abstract document (cf. [6]), which he calls Information Resource. In that characterisation, a Document is equal to an Information Resource. However, I would only treat a concrete document with a concrete content type etc. as Document, because otherwise the use of document is often misleading. Albeit, I more or less agree with his Information Resource definition. However, I would exclude the a priori equivalence of Document and Information Resource from this definition (, if he really stated this equivalence statement – [update]yes9[/update]).
please keep in mind:
“… the separation of layers … is fundamental” (from [7] page 4)
Here is a first attempt of my abbreviated definition of Information Resource:

“An Information Resource is a Resource which can convey or describe (essential) characteristics of a Resource in some way, e.g., in a Semantic Graph. This Description can, for example, be realized (or embodied) as a concrete message, e.g., a serialisation (Representation) of a Semantic Graph in Notation 3 syntax. The Resource can also be the Information Resource itself, in which case it is referred to as a self description.”

It is aligned to the definition of ‘information resource’ that is given by the TAG (Technical Architecture Group) and Harry Halpin’s reflection of this TAG definition (see [13], p. 101). So, an Information Resource itself is more like a piece of abstract information [13], rather than a concrete Document. Albeit, for simplification purpose the term ‘information resource’ is often used to refer to both abstract information and particular Realizations (cf. [13]).


1) Even though, other Resources can contribute to this identification process, e.g., a Description that has as (a) topic the intended Resource.

2) Here Subject should not be considered in terms of the subject position of a triple in an RDF statement.

3) Resource URIs that are part of other Semantic Graphs are dereferenced only once for human-readable label retrieval.

4) Representation can be defined as “data that encodes information about resource state” [14], whereby “information about resource state” can be seen as Description.

5) Equivalence of Information Resources and follow-up inferences that two Resource URIs denote the same Resource is another big issue, which can not be clarified in this scope. For example, a Resource URI can be related to an Information Resource that do not describe the essence of a Resource. Hence, two such Information Resources are ambiguous (cf. definition of substances in [1] and URI Declarations).

6) See [10] for an explanation of Information Service.

7) Please do not understand this claim in a wrong context. It should be seen from a full philosophical point of view.

8) Perception is/is a kind of/can be seen as dereferenciation or vice versa.

9) “I will use the words document and resource interchangeably … and sometimes may slip into using ‘object’.” (from [8]). Furthermore, the ambiguous use of the term Document in [9] is arguable.

[1] Loux, Michael J.; “Metaphysics – A contemporary introduction” (Second edition); Routledge; 2002
[2] Zhuge, Hai et al.; “Basic operations, completeness and dynamicity of cyber physical socio semantic link network CPSocio-SLN”; Wiley; 2010
[3] Ding, Li et al.; Tracking RDF Graph Provenance using RDF Molecules; UMBC Tech Report TR-CS-05-06; 2005
[4] Berners-Lee, Tim; “Linked Data”; w3.org; 2006 – 2009
[5] Berners-Lee, Tim; “Levels of Abstraction: Net, Web, Graph”; w3.org; 2007 – 2010
[6] Beners-Lee, Tim; “Ontology for relating Generic and specific Information Resources”; w3.org; 2009
[7] Berners-Lee, Tim; “Long Live the Web: A Call for Continued Open Standards and Neutrality”; scientificamerican.com; November 2010
[8] Berners-Lee, Tim; “Metadata Architecture”; w3.org; 1997 – 2009
[9] Berners-Lee, Tim; “Meaning”; w3.org; 1999 – 2009
[10] Ferris, Bob; “What is an Information Service?”; infoserviceonto.wordpress.com; 2010
[11] several; “identify”; dict.cc; 2010
[12] several; “embody”; thesaurus.com; 2010
[13] Halpin, Harry; “Sense and Reference on the Web”; ibiblio.org; 2009
[14] Jacobs, Ian et al.; “Architecture of the World Wide Web, Volume One”; w3.org; 2004
[15] Hayes, Patrick J. et al; “In Defense of Ambiguity”; ibiblio.org; 2008


further related sources:

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Info Service Ontology Namespaces, Domains and Prefixes

For representing the different issues of the Info Service Ontology, it was necessary to assign several namespaces/domains, which are the following ones:

Please use them as intended 😉

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What is an Information Service?

A very simple definition is:

An Information Service is a service, which provides (serves) data/knowledge/information somehow.

However, this definition is not strong enough to describe the range and domain of an Information Service. Therefore, it is necessary to define the term Information Service in a specific context. Fortunately, Wikipedia delivers, or better saying serves, a good definition of this context, which is called Information System.

An Information System is any combination of information technology and people‘s activities using that technology to support operations, management, and decision-making.

The definition continues with explaining the term from a bit more technical view:

In a very broad sense, the term Information System is frequently used to refer to the interaction between people, algorithmic processes, data and technology.

Regarding the first part of this definition, an Information Service is an instance of Information Technology. Hence, an Information Service is a part of an Information System. The second role in this definition is people. This term must be substituted by the term agent, which could be an administrator and/or an user. An user could be a customer and/or contributor. In addition, an agent could be a human or a machine. The interaction is that an Information Service, which collects (retrieves), manages (structures) and stores the data/knowledge/information (maybe with the help of an administrator), serves this data/knowledge/information to an user.
The outcome of this, is the following definition:

An Information Service is this part of an Information System that serves data/knowledge/information* to customers and collects it from its contributors, to manage and store it by optionally using administrators.

This should be a technology independent** definition of the term Information Service. That means an Information Service could be

independently of its representation form and/or carrier/transmission medium/form, e.g. a book (paper) or the Internet.
Although, the term Information Service could cover a broad range of things, the usage of it might concentrates for the beginning on the Internet and there especially on the Web, with a focus on Information Services, which have/deliver a huge amount of data/knowledge/information (of a specific domain or domain independent)****. Hence, one could say: “let’s define the term Web Information Service as a subset and a specific kind of Information Service” (cf. definition of Web Information System). However, since the Web delivers only another kind of carrier/transmission medium/form, it should be enough to say that an Information Service simply uses this carrier/transmission medium/form next to other carrier/transmission mediums/forms.
Finally, the Info Service Ontology makes use of the concept Information Service.



PS: This definition is based on the community/expert power of Wikipedia and a good discussion with Olaf Hartig.

*) knowledge is all meaning of data, and information is a subset of knowledge to a concrete question or domain (see Information definition on Wikipedia).

**) That means, it includes non-computer (sometimes also referred as offline***) related things, e.g. a book or a library, and computer (sometimes also referred as online***) related things, e.g. a website.

***) Although, the terms offline and online should be in general used for computer related things. They express whether data/knowledge/information is available via Internet (online) or not (offline).

****) However, the society tends more and more into the Long Tail. Hence, it might be interesting to describe and rate also all these very subjective Information Services, e.g. a personal blog or website. It depends all on the subjective mutual trust each Information Service consumer has to the specific Information Services. Its at least a mutual trust between consumers and producers of an Information Service.

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Info Service Ontology SVN Repository and Mailing List

The Info Service Ontology has now an own SVN repository and a mailing list for discussion. Feel free to join the developing process or leave comments/suggestions/critics. You are welcome 😉



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Welcome to the Info Service Ontology

It was initially a Music Ontology issue (see MO mailing list discussion), later a FOAF Ontology issue (see FOAF mailing list discussion 1 and 2) and now even with a broader scope 😉

The Info Service Ontology - concepts and relations
(please click on the image to enlarge it)

I designed over the last weekend the Info Service Ontology (see the graphic above). The initial intention behind designing this ontology was to add some knowledge re. linked websites from different information services (see the discussion in the prv-vocab mailing list about defining the term ‘information service), e.g. Wikipedia or MusicBrainz, in semantic graphs (as proposed in the FOAF wiki), e.g.

@prefix foaf: <http://xmlns.com/foaf/0.1/> .
@prefix is: <http://purl.org/ontology/is/core#> .
@prefix isi: <http://purl.org/ontology/is/inst/> .
isi:musicbrainz a is:InfoService .

   a foaf:Document ;
   is:info_service isi:musicbrainz .
RDF/Turtle representation of a webpage linked to an Information Service

The Info Service Ontology consists of a basic is:InfoService concept (which could maybe related to prv:DataProvidingService, bibo:Collection, sioc:Space or void:Dataset instances) and some additional ones for describing such an information service (currently: is:InfoServiceQuality, is:InfoServiceType and is:InfoServiceContributorType – the specific individuals are currently only proof-of-concept examples).

The main hook re. specific websites from an information service is is:info_service, which associates an is:InfoService instance to e.g. a owl:Thing (or e.g. sub class of owl:Thing, e.g. foaf:Document) instance (e.g. a website link).

The Info Service Ontology - MusicBrainz example
(please click on the image to enlarge it)

Furthermore, I defined some is:InfoService individuals, especially isi:musicbrainz (see the graphic above and code below) as proof-of-concept example. Therefore, I used also some category definitions from DBpedia (important is also the property is:main_subject for associating a main subject of an Information Service).

@prefix dc: <http://purl.org/dc/elements/1.1/> .
@prefix dcterms: <http://purl.org/dc/terms/> .
@prefix foaf: <http://xmlns.com/foaf/0.1/> .
@prefix is: <http://purl.org/ontology/is/core#> .
@prefix ist: <http://purl.org/ontology/is/types/> .
@prefix isct: <http://purl.org/ontology/is/ctypes/> .
@prefix isq: <http://purl.org/ontology/is/quality/> .
@prefix isi: <http://purl.org/ontology/is/inst/> .
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .
   rdf:type is:InfoService ;
   rdfs:isDefinedBy isi: ;
   dc:description "An open content music database. Modelled here as information service."@en ;
   dc:title "MusicBrainz"^^xsd:string ;
   dcterms:subject <http://dbpedia.org/resource/Category:Metadata_registry> ,
      <http://dbpedia.org/resource/Category:Acoustic_fingerprinting> ,
      <http://dbpedia.org/resource/Category:MusicBrainz> ,
      <http://dbpedia.org/resource/Category:Library_2.0> ,
      <http://dbpedia.org/resource/Category:Online_encyclopedias> ,
      <http://dbpedia.org/resource/Category:Online_music_and_lyrics_databases> ,
      <http://dbpedia.org/resource/Category:Free_websites> ;
      isct:mixed ;
      isq:good ;
      ist:encyclopedia , ist:knowledge_base ;
   is:main_subject <http://dbpedia.org/resource/Category:Music> ;
   foaf:homepage <http://musicbrainz.org/> .

RDF/Turtle representation of MusicBrainz modelled as Information Service

Please feel to add comments, critics and suggestions re. which properties might be useful for describing an info service.

Planned extensions are:

  • enabling multiple info service quality ratings, e.g. by using the Review Ontology, which may come from different info service rating agencies (e.g. modeled with foaf:Agent as hook) so that the customer of such rating could select the info service rating agency of his/her choice
  • defining a is:recommendation property
  • add further Information Service quality properties, this should maybe done in another sub ontology, because rating information quality could be somehow complex and be realized on different levels of complexity (see the ongoing discussion on the prv-vocab mailing list); this information quality classification could probably be used for a reference implementation of an Info Service Quality Ontology

With the is:info_service property as a relation to an Information Service description, it should be possible, e.g. to enable users the opportunity to choose their preferred Information Services as data sources for their knowledge base (or whatever) by selecting the different properties of such an Information Service.

That’s all for the moment 😉



PS: I would also give Olaf Hartig props for clarifying the term ‘Information Service‘ on which this ontology is grounded. Thank you very much (again) Olaf!

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