Overview of the MPEG-21 Media Contract Ontology

Tracking #: 1129-2341

Víctor Rodríguez-Doncel
Jaime Delgado
Silvia Llorente
Eva Rodríguez
Laurent Boch

Responsible editor: 
Guest editors Semantic Web 4 Legal Domain

Submission type: 
Ontology Description
The MPEG-21 Media Contract Ontology (MCO), a part of the standard ISO/IEC 21000, is an ontology to represent contracts dealing with rights on multimedia assets and intellectual property protected content in general. A core model provides the elements to describe the permissions, obligations and prohibitions exchanged in the clauses of a contract. Specific vocabulary is defined in a model extension to represent the most common rights and constraints in the audiovisual context. Design principles, a methodology and a comparative analysis are given, as well as the practical guidelines to use the standard. A thorough description of the contract creation workflow from an original contract is given, including a sample contract text, the RDF version, the detailed mapping of the most relevant clauses and the reconstructed version. A set of MCO-related tools is described, including (i) the reference software to create and edit MCO contracts; (ii) modules to identify, store, search, validate and deliver MCO contracts and (iii) a tool to convert between the akin Contract Expression Language (CEL) contracts and the MCO contracts and (iv) the actual use of MCO in the Rightsdraw family of services.
Full PDF Version: 

Major Revision

Solicited Reviews:
Click to Expand/Collapse
Review #1
By Laura Hollink submitted on 10/Aug/2015
Minor Revision
Review Comment:

The Media Contract Ontology is part of the MPEG-21 standard. It provides the means to formalize contracts about the exploitation rights of multimedia items. This paper describes the requirements, design and use cases of the MCO.

The description of the classes and properties of the ontology is very precise and complete. The authors have succeeded to give enough details to enable even people unfamiliar with the legal domain to understand the the concepts. Also, the scope of the ontology clearly indicated. The paper includes extensive examples of how contracts can be represented in MCO. For those reasons, I would recommend publication. However, in my opinion there a large number of small issues that would need to be addressed before the paper is ready for publication. I have detailed them below.

The paper is very long for a 'Descriptions of ontologies' paper. In my comment below I have pointed to sections where I think the authors can shorten the paper.

Section 1:
he justification for using semantic web standards remains vague and overly general. E.g. on page 1 "in order to deal with the even increasing amount of material". I would leave it out or be more specifica about what an OWL version brings over other formats. I know most readers of this journal will not need to be convinced since they work in the semantic web field, but even then, unclear arguments have no place in a paper.

"other areas of media asset management ... which have begun to benefit from knowledge representation based on ontologies" -> citations needed.

On page 2, I guess the words in italics are taken from the MPEG-21 specification. Is this correct? Please make that explicit.

Section 2:
In this section, a summary of the requirements is given, with a reference to a previous paper. However, no information is given on the ontology design method. E.g. how did you check that the ontology matches all the requirements. For example, this can be done using competency questions.

Related this my question about the design process: the paper does not include any interesting design features, i.e. there are no lessons to be learned about how modelling.

In most ontology design processes, two things are given a high priority: (1) the reuse of concepts from external ontologies in the created ontology, and (2) the potential reusability of the created ontology by others/for other purposes. You explain that the former is in contrast with the MPEG design principle that a standard needs to be self contained, so it makes sense that it plays no part in the paper. I am interested, however, in your opinion of the latter. Could the concepts in the MPO be reused or linked to by others? Is that your intention? You have pretty strict domain an range restrictions, do they form problem from reuse? From a practical perspective, could it be linked to the LOD cloud? I don't have the answers but I think these issues should be mentioned in the paper.

Section 4:
sec 4.3.1 one but final sentence. I don't understand this, what is CatchupTV? What are acillary-rights?

sec 4.3. the first sentence seems redundant to me, please consider removing it.

the final triple in table 2 (freeofcharge) is not visualized in fig 8

Section 5:
You mention twice that natural text can be derived from MCO statements. Please explain how. Can this be done automatically? If so, with what tool? How well does this tool perform, is there some kind of evaluation?

In sec 5.1.3: "identify contract elements for which encryption is requested". What is an element here? Any resource? Or does it need to be a complete RDF statement ?s ?p ?o? It would be good to be more explicit about this.

Sec 5.2.1: what role does this subsection play in the paper? It seems to me it could be removed without problems. As an 'example of use' is it too high level.

Section 6:
sec 6.1.2: is this description necessary? Can it be removed?

sec 6.2 same here, this does not add to the understanding of the ontology or how to use it. Can it be removed? This includes the mention of rightdraw in sec 5.2.2 Also, it sounds as if these services are no longer being maintained, is that correct?

sec 6.1.1. incorrect ref to sec 5.2

Throughout the document
there are problems with spacing: e.g. no space between the | symbol in fig 1, 'thesocalled' near the end of sec 4.3.1, "i ncount r y" in table 2, and many more.

Review #2
By Renato Iannella submitted on 17/Aug/2015
Minor Revision
Review Comment:

(1) Quality and relevance of the described ontology (convincing evidence must be provided).

This paper described the MPEG-21 Media Contract Ontology standard.
Overall, the authors present a good overview of the main elements of the MCO and some practical applications.
There is very little critical analysis of the MCO as the paper authors are also the MCO standard editors. This is transparent in the paper, but the lack of criticality does present a primarily positive picture of the MCO.
As the MCO is already an MPEG standard, then the evidence for its design and applicability are already self-evident as the process undertaken follows the typical ISO procedures.

(2) Illustration, clarity and readability of the describing paper, which shall convey to the reader the key aspects of the described ontology.

Some of the points that the paper should address and/or clarify include:
- Section 5.1.3 talks about encrypting parts of the contract, but does not mention key management.
- It is not clear if Table 3 is supposed to be the complete "textual contract" represented in Table 4.
-- If it is, then there are some missing contract terms, such as "all rights in the dub", "simultaneous retransmissions"...
- It is not clear if Figure 9 is part of the MPEG-21 standard (the process from textual to machine representation)
-- If not, then it should be made clear that is not in the scope of the standard
- In Figure 11, the "Run" has a number and validity - interpreting that axion (without reading the textual contract) is unclear as it could mean you can show theProgramme 4 times in 24 hours?
- The spatialContext is missing 3 geopolitical areas
- The FactUnion (with the 3 hasFact properties) could have been modelled more flexibly - instead of single resources - they should have been modeled as axions like "Technology hasValue Satellite" (etc)

Review #3
Anonymous submitted on 26/Aug/2015
Major Revision
Review Comment:

This new submission actually does not provide specific improvements with respect to the previous one, in particular as regards the questions addressed by the reviewers. On the other hand the need for a deeper description of the ontology, as well as its reasoning power, is much more felt due to the change of submission type.