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Summarization combines objects with attributes in common by means of a hierarchy structure you define yourself. The controlling area is always the top node in the hierarchy. Examples of summarization criteria include:
For more information, read
Summarization Hierarchies .
Project summarization occurs by master data fields. The advantage of project summarization by master data fields is that you carry out the inheritance run of master data fields separately from the actual project summarization. This significantly improves performance.

If you were using summarization before Release 4.5, your projects are summarized by classification.
We recommend that you convert to summarization by master data fields. Support for summarization by classification is likely to be withdrawn in the medium-term. For more information, see Information System
For more information about summarization by master data fields, see
Project Summarization.
For more information about summarization by classification, see
Project Summarization Using Classification.
See also:
Marking a Project for Summarization