Change:
5.2.3. <del> This boolean property specifies whether an application considers it useful to indicate its reliability requirements on a per-Message basis.  This property applies to Connections and Connection Groups. This is not a strict requirement.  The default is to not have this option. </del> <ins> Type: Preference This property specifies whether an application considers it useful to indicate its reliability requirements on a per-Message basis.  This property applies to Connections and Connection Groups.  This is not a strict requirement.  The default is to not have this option. </ins> 5.2.4. <del> This boolean property specifies whether an application would like to supply a Message to the transport protocol before Connection establishment, which will then be reliably transferred to the other side before or during Connection establishment, potentially multiple times.  See also send-idempotent.  This is a strict requirement.  The default is to not have this option. </del> <ins> Type: Preference This property specifies whether an application would like to supply a Message to the transport protocol before Connection establishment, which will then be reliably transferred to the other side before or during Connection establishment, potentially multiple times.  See also send-idempotent.  This is a strict requirement.  The default is to not have this option. </ins> 5.2.5. <del> This boolean property specifies that the application would prefer multiple Connections within a Connection Group to be provided by streams of a single underlying transport connection where possible. This is not a strict requirement.  The default is to not have this option. </del> <ins> Type: Preference This property specifies that the application would prefer multiple Connections within a Connection Group to be provided by streams of a single underlying transport connection where possible.  This is not a strict requirement.  The default is to not have this option. </ins> 5.2.6. <del> This boolean property specifies whether an application considers it useful to be informed in case sent data was retransmitted more often than a certain threshold.  This property applies to Connections and Connection Groups.  This is not a strict requirement.  The default is to have this option. </del> <ins> Type: Boolean This property specifies whether an application considers it useful to be informed in case sent data was retransmitted more often than a certain threshold.  When set to true, the effect is twofold: The application may receive events in case excessive retransmissions.  In addition, the transport system considers this as a preference to use transports stacks that can provide this notification.  This is not a strict requirement.  If set to false, no notification of excessive retransmissions will be sent and this transport feature is ignored for protocol selection. This property applies to Connections and Connection Groups.  The default is to have this option. </ins> 5.2.7. <del> This boolean property specifies whether an application considers it useful to be informed when an ICMP error message arrives that does not force termination of a connection.  This property applies to Connections and Connection Groups.  Received ICMP errors will be available as SoftErrors.  Note that even if a protocol supporting this property is selected, not all ICMP errors will necessarily be delivered, so applications cannot rely on receiving them.  This is not a strict requirement.  The default is not to have this option. </del> <ins> Type: Boolean This property specifies whether an application considers it useful to be informed when an ICMP error message arrives that does not force termination of a connection.  When set to true, received ICMP errors will be available as SoftErrors.  Note that even if a protocol supporting this property is selected, not all ICMP errors will necessarily be delivered, so applications cannot rely on receiving them.  Setting this option also implies a preference to prefer transports stacks that can provide this notification.  If not set, no events will be sent for ICMP soft error message and this transport feature is ignored for protocol selection. This property applies to Connections and Connection Groups.  The default is not to have this option. </ins> 5.2.8. <del> This boolean property specifies whether the application considers it useful to enable / disable / configure a checksum when sending data, or decide whether to require a checksum or not when receiving data. </del> <ins> Type: Preference This property specifies whether the application considers it useful to enable / disable / configure a checksum when sending data, or decide whether to require a checksum or not when receiving data. </ins> This property applies to Connections and Connection Groups.  This is not a strict requirement, as it signifies a reduction in reliability. The default is full checksum coverage without being able to change

Discussion:
This commit fixes bug by making transport parameter types explicit. It also fixes Path- and Protocol Selection Properties from "binary + preference" to preferences type. With the old boolean properties, one could do things like "prohibit Reliable Transport false" - is that the same as "prefer Reliable Transport true"?
To the questions in NAME review summary: For the general case: I believe there will be boolean properties (that are not preferences). The way I understand "Excessive Retransmit Notifications" and "ICMP soft error message", I think booleans are the more appropriate type. Not for -00, but for -01: I want to define all types more rigorously in -01 --- we have Boolean, Enumeration, Boolean in the Transport Parameters right now, we also have some Integers in the Send Parameters. I am not sure that the frontmatter of this section is the right place to do so.
General clarification: This pull request changed "preference" to a data type a value can have rather than being something weakly defined that can be specified along with every Transport Parameter. So we go from a Key / Preference / Value tripel where Preference or Value is pointless for (n-1) cases to a Key / Value pair with typed values. The only Transport Parameter (including the Intents in the Appendix) that uses a parameter and a preference is the "Interface Type". I would like to land this for -00 as this is good enough for discussion while the old state is confusing. ToDos for -01: Explain types clearly make "Interface Type" easier in -01 discuss extendability
If we're doing booleans, the document needs to define a concise and generally applicable rule for how booleans interact with preferences. ISTM that boolean True == preference Prefer and boolean False == preference Avoid (in which case, why not just say Prefer and Avoid instead of True and False?) I might be wrong here though. Will defer to NAME
also NAME Please file everything in the comments on this PR that should be addressed in -01 as an issue (if you haven't already)... thanks!
Ok - now I got your point. These properties (Notification of excessive retransmissions and Notification of ICMP soft error message arrival) are actually doing two things: Enable sending these events Indicate that we prefer protocols stacks that can send these events The question is which one is more important.

As I think the former is more important, I leave it boolean an add remarks to the individual properties that this implies preferring protocols that can provide these events for now. As this does not hide things, this should provide the better feedback for -00
This should be ready for landing. – NAME please merge if you agree Open Issues for Milestone itef-01: Restructure Transport Parameters Section Explain data types explicitly Rewrite Interface Types to be useful and implementable
Transport and Send Parameter have different data types. These types are used in the document in a more or less intuitive way but are never defined explicitly. May need a new section next to the pseudocode definition.
This has been addressed in PR
This is a fork of Issue – The part of it that does not need discussion. Annotate "data type" for each Transport Parameter Change "boolean" Protocol and Path Selection Parameters to type "Preference" Remove editing artifacts
still not convinced by the boolean argument, but it's time to ship it.