Difference between revisions of "Transient Attributes"
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== Validity Rule == | == Validity Rule == | ||
− | An attribute can be marked `volatile' if and only if its type has a default value and | + | An attribute can be marked `volatile' if and only if its type has a default value and is not a user defined expanded type. |
== Rationale of validity rule == | == Rationale of validity rule == |
Revision as of 14:46, 23 June 2009
For storable purposes, it makes sense that some attributes of objects are not stored to disk. We call them volatile attribute and currently are specified using a note clause:
field: detachable X note option: volatile attribute end
Validity Rule
An attribute can be marked `volatile' if and only if its type has a default value and is not a user defined expanded type.
Rationale of validity rule
If the type did not have a default value (which is the case for attached types), then upon retrieval the volatile attribute would be Void which is against void-safety.
For simplicity and backward compatibility of `basic_store' which does a memory copy of the object to disk, it would be quite complicated to implement when expanded are involved. We prefer our users to use SED once it supports expanded.