Working Group meeting

Date: 28/10/2021
Participants: Natalie Muric, Giovanni Paolo Sellitto
Model editor: Eugen Costezki
Note editor: Andreea Pasăre

Agenda:

  • Discuss whether we should add Review Requester to eProcurement Ontology

    • See Role table (rev-req). The concept is available in the vocabulary table and not in the ontology.

  • Inter-role dependency:

    • example relation: Tenderer and Winner (currently modelled as subclass)

    • Is it a true subclass relationship? or

      • Is the winner a more refined type of a tenderer? Like, for example, “square” is a more specific type of a “geometric shape”.

    • Is it a (precedence) dependency of some sort?

      • An organisation can take the winner role only if it is a tenderer first. Therefore we need an instance of the role of the or organisation as a tenderer (in one situation) in order to instantiate a winner role for that organisation.

    • Can they both be the case?

      • Are we allowed to imagine that previously created instances can be updated / extended / modified? Or do we just refer to them mainly once they have been created? (this shall be recorded as a principle)

      • Then how?

  • Decide what role properties we need in the model & announce work in progress on role modeling alternatives

    • Selection from 15 role features available.

    • Announce the work in progress on approaches to role modelling.

Discussion

Inter-role dependency:

Winner is not a more specific type of Tenderer. It’s a dependency on the outcome of a different phase.
Presenting “approaches to role modeling” document.

Example diagram:

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Example instance level:
An Organisation should be at first a Tenderer in order to become a Winner.

Counter-example instance level:

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But a Tenderer could be made up of several organisations.

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Diagram example:

Example instance level:

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Winner is a subclass of Tenderer which is a subclass of Role.

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Example roles as subclass role to role - instance level:

We can not take the URi from the Tenderer and move it to Winner. We need to create another one.

The identity of the Role comes from the Organisation.

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In UML we can not say that it is the same Organisation, but we can add a joint dependency “sameSource”, like in the diagram below:

Therefore we can not instantiate the following example:

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Such inter-roles dependency needs to be expressed in the model without reusing the properties of the prior role.
For example:
The properties of an Organisation with several roles should be instantiated only once.
Counter-example:

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Using specialisation relation is not a solution. (e.g. Winner is not a more specific type of a Tenderer)

Principles presented:

  • Instance immutability - once published, an instance shall not be conceptualised as changeable.

  • Non-redundancy - properties of an entity must be instantiated only once.

Role features

The following Features are relevant to ePO:

  • A role comes with its own properties and behaviour

  • Roles depende on relationships

  • An object may play different roles simultaneously

  • The sequence in which roles may be acquired and relinquished can be subject to restrictions.

  • Objects of unrelated types can play the same role. (Evaluator role can be played by an organisation, a system or a person)

  • Roles can play roles (is this the case?!) We should fall back on role dependency whenever possible. The “group lead” is modeled as a named place and not a class in ePO.

  • The state of an object can be role-specific.

  • Different roles may share structure and behaviour. (we have proper role hierarchies: for example CentralPurchasingBody is split into two classes: Awarding and Acquiring)

  • An object and its roles have different identities. (An organisation may be tenderer in different procedures/lots. So the # of tenderers may be greater than the number of organisations.)

Decisions

  • Include “Review Requester” role in eProcurement Ontology