FAQ

Underneath you can find a list of frequently asked questions and their answers. Should you have a question which is not answered on this page, feel free to contact the RailTopoModel Expert Group at any time.

Should each NetworkResource be assigned to one (and only one) network level?

Question

"Standard interpretation of the currently modeled relationship between NetworkResource and LevelNetwork suggests, that each NetworkResource should be assigned to one (and only one) network level.
Is this really the way it is meant to be? is that also true e.g. with operating points? (independently from the concrete question, I would advise to explicitly model all cardinalities in order to avoid misinterpretation)"

Answer

  • Corrected in current version of RTM, to be published asap on web site as update of IRS.
  • NetworkResources can be related to multiple levels."
  • For a clear understanding of the model and to avoid questions for all relations the cardinality shall be added (nothing was used in the meaning of many (*)). Alternatively a footnote can be added if this interpretation corresponds to the UML standard. Andreas checks the standard and proposes a solution.
What do I need the non-linear net elements for?

Question

Is (unambiguous) navigability meant to be represented as relation between two linear net elements (as I understand it a navigability including non-linear net elements is not unambiguous)? but if so, what do I need the non-linear net elements for?

Answer

  • Navigability through NetElement (no matter if linear or non-linear) and Relations.
  • Adaptation of generalizations between terminal classes and linear/non-linear elements.
Why do we have a „double“ relationship modeled between NetElement and Relation as well as between PositionedRelation and PositioningNetElement?

Question

Maybe related to this topic: why do we have a „double“ relationship modeled between NetElement and Relation as well as between PositionedRelation and PositioningNetElement? does this way of modeling results from question 2 (representation of navigability)?

Answer

The model is designed such a way that you can navigate on the graph, starting from a node or an edge (in the graph theory point of view). Therefore a NetElement (as a topology resource, or a node in connexity graph) knows all its related resources through "Relation" (an edge in the connexity graph). Same for PositionnedRelation which knows the two Positioning NetElement it links.

Do elements of an inferior network level need to be unambiguously assigned to one element of the superior network level?

Question

Do elements of an inferior network level (e.g. tracks/trails) need to be unambiguously assigned to one (and only one) element of the superior network level (e.g. section of line)? At SBB, we do have tracks belonging to multiple sections of line as well as consecutive switches sharing one switch point.

Answer

  • No, as a matter of fact, a section of track may belong to multiple sections of lines.
  • Comment Nicolas: Disagree. Assignment between different levels needs to be unambiguously.
  • Follow-up discussion with Nicolas in the following face-to-face meeting. > still open issue
Should the generalization between PositioningNetElement and CompositionNetElement not rather point to the NetElement?

Question

Should the generalization between PositioningNetElement and CompositionNetElement not rather point to the NetElement (instead of the CompositionNetElement)? does such a way of modeling allow for a positioning of all elements even of the most inferior level (you may call them “atomic” elements)?

Answer

  • A PositioningNetElement should behave as any other agregation of lower level. Therefore, PositioningNetElement is a derivation of CompositionNetElement.
  • Allows for aggregation and disaggregation of NetElements between different levels.
Can I use LinearAnchorPoint to solve the problem of ambiguous kilometrage?

Question

Understanding LinearAnchorPoint as calibration points for linear referencing systems, can I use them to solve the problem of ambiguous kilometrage (e.g. in case of prolongation of section of lines)?

Answer

Yes.

Are the relations between SpotLocation and SpotLocationIntrinsic/Coordinate really generalizations or rather compositions?

Question

Are the relations between SpotLocation and SpotLocationIntrinsic/Coordinate really generalizations or rather compositions?

Answer

Yes, it is a generalization.

What do the values of LinearPositioningSystem mean?

Question

The class LinearPositioningSystem features 3 values (absolute, relative, interpolation) for the LrsMethod — what is their exact meaning?

Answer

The distinction for LrsMethod with the possible values of "absolute", "relative" and "interpolation" was taken out of ISO ISO 19148:2012(E) (Geographic information - Linear referencing) Chapter 6.1.1.3. That seems to be an issue for the Wiki.

How is postioning/localization within buildings handled within RTM?

Question

Not sure whether other railway infrastructure companies are facing the same problem, but should and – if yes – how is postioning/localization within buildings handled within RTM (e.g. for telecom assets)?

Answer

  • "This topic is not adressed currently in RTM. The referencing system being totally generic, can be used. But there is a need for clarification of the need and best/standard practices in the domain of building."
  • This should rather be a topic for the upcoming discussion of integrating RTM and BIM modelling approaches.
For the forum

Question

From the forum: I would point to you an ""issue"" about some generalizations & composite association used in the Location Package. In the previous picture, Area and Linear Location and their generalizations are presented, along with their associated elements of Topological Package. Now let's try to create a Linear Location:Create a Linear Location - Create an OrderedAssociatedNetElement (Mandatory due to composite multiplicity) - Create an AssociatedNetElement (Suggested by the generalization) - Create an AreaLocation (Mandatory due to composite multiplicity) So we will have a ""free"" AreaLocation created, but the problems come from the fact that This object is weakly linked to the LinearLocation created at first (only a common generalization ...no even mandatory realized by the same instance). A solution might be to make the LinearLocation to be a specialization of a AreaLocation, and

  • Create a Linear Location
  • Create an OrderedAssociatedNetElement (Mandatory due to composite multiplicity)
  • Create an AssociatedNetElement (Suggested by the generalization)
  • Create an AreaLocation (Mandatory due to composite multiplicity)

So we will have a ""free"" AreaLocation created, but the problems come from the fact that This object is weakly linked to the LinearLocation created at first (only a common generalization ...no even mandatory realized by the same instance). A solution might be to make the LinearLocation to be a specialization of a AreaLocation, and tu explain that the composition of LinearLocation is a redefinition of the one of AreaLocation.

Answer

  • I don't remeber if we had update of the model on Location, but on the attached model (see picture embedded), thereis no relation between Linear Location and AreaLocation. Therefore, youi just nned to creat Linear Location andOrderedAssociatedNetElement . No need to Create an AssociatedNetElement, neither an AreaLocation
  • "Add comment to the forum > Gilles, Alain
  • Create instantiation of the class model (instantiated objects) to better understand the issue > Andreas for next meeting"