NAME

       md_doc_help_elektra-classes - elektra classes(7) -- introduction in Elektra's classes This overview
       complements the introduction in the API documentation.

       A Key consists of a name, a value and metadata. It is the atomic unit in the key database. Its main
       purpose is that it can be serialised to be written out to permanent storage. It can be added to several
       aggregates using reference counting. Putting Key objects into other data structures of supported
       programming languages presents no problem.

   KeySet
       The central data structure in Elektra is a KeySet. It aggregates Key objects in order to describe
       configuration in an easy but complete way. As the name ''set'' already implies every Key in a KeySet has
       a unique name. A user can iterate over the Key objects of a KeySet. KeySet sorts the keys by their names.
       This yields a deterministic order advantage. So, independent of the appending sequence and, in
       particular, the number of fetches and updates, KeySet guarantees the same order of the Key objects. Some
       configuration storage systems need this property, because they cannot remember a specific order. On the
       other hand, any particular order can easily be introduced (See order).

       On the one side backends generate or store a KeySet object and, on the other side, elektrified
       applications receive and send a KeySet object. Both sides, as well as the core in between, have the
       possibility to iterate, update, modify, extend and reduce the key set. Appending of new or existing Key
       objects extends the key set. Otherwise it can be reduced if keys are popped out. The Key object becomes
       independent from the KeySet afterwards. The user can still change such a key or append it into another
       key set. The affiliation to a key set is not exclusive.

       Every key in a KeySet object has a unique name. Appending Key objects with the same name will override
       the already existing Key object.

   KDB
       While objects of Key and KeySet only reside in memory, Elektra's third class KDB actually provides access
       to the global key database. KDB, an abbreviation of key database, is responsible for actually storing and
       receiving configuration. KeySet represents the configuration when communicating with KDB. The typical
       elektrified application collects its configuration by one or many calls of kdbGet(). As soon as the
       program finishes its work with the KeySet, kdbSet() is in charge of writing all changes back to the key
       database.

       This technique has some advantages. First, applications have full control over modifying Key and KeySet
       objects without touching the key database. Second, the decision how many KeySet objects the application
       administrates is left to the application. It can choose how to split up the KeySet objects. The main
       reason for this technique is that for backend development the same data structure is used, and as we will
       see, the borderline between application and backend development becomes blurred.

       The application adapts the configuration between kdbGet() and kdbSet() in memory. The modifications are
       not only faster, they also allow large atomic configuration upgrades, robust merging of settings and
       handling of complicated inter-relationships between keys without problematic interstages. Elektrified
       applications, however, should be aware of conflicts. It can happen that the key database is changed while
       working with a KeySet. Then, attempts to use kdbSet() lead to a conflict. KDB detects such situations
       gracefully and lets the application decide which configuration should be used.

       For details and background read more about elektra data structures. For further information see the API
       documentation.

Version 0.8.14                                   Tue Dec 15 2015           md_doc_help_elektra-classes(3elektra)