What is an "appropriate manner" when reserving, not granting, a right?

Please forgive any potential misunderstandings by one new to this group...

I would appreciate greatly if someone could explain what is meant by the
term "appropriate manner" in EU DSM Article 4 and what would be necessary
to establish that the TDM Reservation Protocol
<https://github.com/w3c/tdm-reservation-protocol/tree/main>, or some other
method, is such an appropriate manner.

It seems to me that the requirements for expressing an effective and
actionable reservation of rights are likely to be significantly more
rigorous than the requirements for expressing an effective grant of rights.

One who wishes to benefit from a granted right can comfortably choose to
rely on a wide range of methods that others might use to express such
grants. One might, for instance, rely on human readable text, or a Creative
Commons license, or some ODRL embedded within, or associated with, some
object. While there may be many ways in which such grants are expressed, it
will often be very much in the interest of those who wish to benefit from
such grants to understand a broad range of methods for expressing such
grants.

However, one who wishes to exercise a right which is normally granted by
law, but which, in an exceptional case, may be reserved by another, is
likely to insist that the manner in which a reservation is expressed must
conform to some precise and well-known form which has been explicitly
sanctioned by some applicable law or regulation. Clearly, this insistence
will often be considered reasonable since there already exist a
multiplicity of proposals for Rights Expression Languages, each having
various states of formal definition and degrees of adoption. One can
reasonably object to any specific manner for expressing reservations by
simply saying that they had no reason to understand or respect that form of
expression.

The reasonableness of a text or data miner's objections to some form of
expression is probably greatest when the reservation is expressed somewhere
outside the particular data of interest. For instance, if it is in a file
like robots.txt or in a .well-known file. The miner can simply say that
there exists no law requiring one to seek out reservations that might, or
might not, exist in a variety of obscure locations. On the other hand, as
noted before, one who wishes to benefit from the grant of a right is
probably highly motivated to do whatever is necessary to find such grants.

The recitals in the EU DSM say:

> "it should only be considered appropriate to reserve those rights by the
> use of machine-readable means, including metadata and terms and conditions
> of a website or a service."

But, no guidance is provided for determining which machine-readable means
meet the requirements or how one is supposed to find "terms and conditions"
that might include them. Of course, if this text were read to mean "any
machine readable means," the effect would be to nullify the law since it
would be practically impossible for any miner to prove the negative -- that
there was no machine-readable expression present -- even if it was in some
unknown or obscure format.

So, under EU law, what is necessary to establish an "appropriate manner"
for expressing reservations? Also, can such a manner be defined by some
non-state organization, such as the W3C, without explicit adoption or
endorsement by the state via legislation or regulation?

bob wyman