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Each metadata template represents a change in the RTS, where a change is typically something that happens to a template. We currently recognize three major changes that happen to in an RTS: insertion of a template : insertion into the RTS (essentially creation), invalidation of an existing template, and re-validation of a template (that was previously invalidated). We describe these changes below. Also, assignment of an instance unique identifier (IUI) is something that happens in the RTS. Currently, these changes are captured in A templates. At this time, we do not propose to change how IUI assignments are captured as A templates.
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We propose to remove the E parameter from metadata template specification, and replace it with two parameters: the CV CT parameter for change type and the EC parameter for error code.
The
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CT parameter
The CV CT parameter may take 3 values, defined as follows. It is a required field in the metadata template.
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One disadvantage to this approach is that to query "good" data in the RTS, the query must check disjunctively for the values I and R in the CV CT parameter. Alternatively, we could add a flag to the templates themselves that determines whether they are valid. This flag would be set to true upon insertion and revalidation, and to false upon invalidation. The disadvantage to that approach is keeping the flag in synchronization with the information in the metadata templates in the RTS.
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The EC parameter takes the same values as the original E parameter except for the value I (insertion). It is not a required field in the case of template insertion or revalidation. It would be required for any metadata template with an CV CT parameter with value X.
The C parameter
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Consider an incorrect PtoU template template asserting that a particular chair is an instance of Table. The error was in asserting this PtoU template, not in inserting it into the RTS. Thus, the error was made on the part of the entity designated by by iuia (in the PtoU template). Now either this entity (1) really believed that the chair was a table for some reason or (2) made a mistake in picking out a reference to the type type Chair (e.g., said "table" when she meant to say "chair" or selected "table" from the dropdown list when she meant to select "chair").
Now, if the entity correcting the error is the same entity as the the iuia of the template with the error, then there is the possibility of both change in belief (really believed it was a table when she made the PtoU assertion) and recognition of error (never believed it was a table but just picked the wrong reference somehow).
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We cannot assume either. The remaining question is whether it is worth making the distinction? It would certainly be helpful in the grand scheme of things to capture both, so we could differentiate erroneous beliefs from errors in recording those beliefs, so that we could study them.
The allowed values for C are therefore the following:
| Parameter | Definition |
|---|---|
| CE | The change in the RTS occurred to reflect a change in reality. |
| CB | The change in the RTS occurred to reflect a change in belief. |
| CR | The change in the RTS occurred to reflect a change in relevance. |
| XR | The change in the RTS occurred to reflect a recognition of error. It is different from a change in belief, because the entity making the change never believed what the RTS said, but instead recognized that the statement in the RTS was wrong. It could be, for example, that s/he meant to select the universal Liver from a pick list, but accidentally picked Lung and only later after recording data in the RTS realized the mistake. |
Implications for Remainder of
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Metadata Template
| Parameter | Implication | iuid
|---|---|
| iuid | Now refers to the entity that is initiating the change/event in the RTS. |
| td | Now refers to the time at which the change occurs. |
| iuit | Still refers to the A, PtoU, PtoP, etc. template, but now the implication is that this template has participated in a change to the RTS (e.g., its insertion is a change to the RTS) |
| S | Now refers to a list of templates that correct the error in the template denoted by iuit (formerly referred to templates that "replaced" template denoted by iuit but we do not recognize replacement of templates, just invalidation and revalidation). |
Possible Combinations of Parameter Values
| CT | C | EC | S |
|---|---|---|---|
| I | <any> | <null> | <null> |
| X | XR or CB | <any> | <any> |
| R | XR or CB | <null> | <null> |