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Update wikipage Persistence, storage, and retrieval. (Signed-off-by:tqa7ve2mnbntqnfca3i6rk7arhc2kxr8).

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@@ -29,7 +29,7 @@ Different variants of the store operation are available: '''session''', '''basic
Historically, the persistence mechanism was offered via the helper class [[ref:libraries/base/reference/storable_chart|STORABLE]] which you could use as an ancestor whenever you wanted to store and retrieve objects. Via this class you would have access to <eiffel>basic_store</eiffel> and <eiffel>independent_store</eiffel> to store an object, and <eiffel>retrieved</eiffel> to retrieve one. However this was not necessary and the persistence mechanism could be used directly from any descendants of the [[ref:libraries/base/reference/io_medium_chart|IO_MEDIUM]] using routines with the same names. This manner of storing and retrieving objects is called the '''C''' persistence mechanism since it was completely written in C and is included as part of the Eiffel runtime. Historically, the persistence mechanism was offered via the helper class [[ref:libraries/base/reference/storable_chart|STORABLE]] which you could use as an ancestor whenever you wanted to store and retrieve objects. Via this class you would have access to <eiffel>basic_store</eiffel> and <eiffel>independent_store</eiffel> to store an object, and <eiffel>retrieved</eiffel> to retrieve one. However this was not necessary and the persistence mechanism could be used directly from any descendants of the [[ref:libraries/base/reference/io_medium_chart|IO_MEDIUM]] using routines with the same names. This manner of storing and retrieving objects is called the '''C''' persistence mechanism since it was completely written in C and is included as part of the Eiffel runtime.
Today, we recommend using the '''SED''' ('''SE'''rialization '''D'''eserialization) persistence mechanism, entirely written in Eiffel. It is very flexible, sinceit lets you control the format of the stored structure, but in most cases it suffices to rely on the simple helper class [[ref:libraries/base/reference/sed_storable_facilities_chart|SED_STORABLE_FACILITIES]]. This class offers <eiffel>session_store</eiffel>, <eiffel>basic_store</eiffel>, and <eiffel>store</eiffel> (the de-facto independent store), as well as <eiffel>retrieved</eiffel>. Today, we recommend using the '''SED''' ('''SE'''rialization '''D'''eserialization) persistence mechanism, entirely written in Eiffel. It is very flexible, since it lets you control the format of the stored structure, but in most cases it suffices to rely on the simple helper class [[ref:libraries/base/reference/sed_storable_facilities_chart|SED_STORABLE_FACILITIES]]. This class offers <eiffel>session_store</eiffel>, <eiffel>basic_store</eiffel>, and <eiffel>store</eiffel> (the de-facto independent store), as well as <eiffel>retrieved</eiffel>.
In both cases, you only need to be aware of the difference between the various storing mechanism (session, basic and independent) at storage time. The stored structure will always be available through feature retrieved; this feature will figure out, from the format of the stored structure how it was stored and will decode it accordingly. In both cases, you only need to be aware of the difference between the various storing mechanism (session, basic and independent) at storage time. The stored structure will always be available through feature retrieved; this feature will figure out, from the format of the stored structure how it was stored and will decode it accordingly.