Contents

• Name and Acronym:
• Coordinator(s):
• Purpose:
• Client(s):
• List of Classes:
• Requirements and Use Cases:

Name and Acronym:

Coordinator(s):

Purpose:

Client(s):

List of Classes:

• Per.
  The Per class has general utility data members and static methods for use by the persistency package.

• File management classes:
  • PerFileManager, PerFileMember.
    PerFileManager is a singleton file manager class used to open and close files. Together with its helper class PerFileMember, it keeps track of the files which are open, their access mode, and the number of clients of each file. A UML diagram showing PerFileManager and its helper class PerFileMember follows:
  A full class diagram of the PerFileManager and PerFileMember classes is shown here .

• Stream management classes:
  • PerStreamManager, PerInputStreamManager, PerOutputStreamManager.
    PerInputStreamManager and PerOutputStreamManager (each of which derive from PerStreamManager) are singleton input and output stream managers respectively. They manage the I/O from a set of PerStreams. They have the ability to enable or disable any PerStream in their set.
  • PerStream, PerInputStream, PerOutputStream.
    PerInputStream and PerOutputStream (each of which derive from PerStream) manages the I/O from a single ROOT TTree. They maintain a set of PerStreamBranches specific to that TTree. They have the ability to enable to disable any PerStreamBranch in their set.
  • PerStreamBranch.
    PerStreamBranch manages the I/O from a single ROOT TBranch.
  A full class diagram of the Stream management classes is shown here .

Requirements and Use Cases:

• Requirements for stream (tree) I/O management (a stream in abstract terms is a collection of related objects. Its implementation is through a ROOT TTree data structure with a 1:1 relationship between TTree's and streams.) :
  • Provide support for managing random read and sequential read/write (provided by TTree data structure).(1)
  • Support partial I/O of entries in any one stream (tree branches can be disabled/enabled).(1)
  • Support methods by which users can enable/disable streams.(1)
  • Support synchronized I/O of entries spread out over multiple streams.(1)
  • Provide consistency check (via unique identification stamp) between different streams to check the validity of combining user-specified input data streams.(2)
• Requirements for stream (tree) structure and creation:
  • "Hard-wired" tree structures either for input or output streams should be avoided. (1)
  • Provide tools by which users can create their own tree to be used for output streams.(1)
    • Provide support for generic object branches to hold objects deriving from TObject (including TObjectArrays).(1)
    • Provide support for clonesarray branches to hold TClonesArray objects.(2)
  • Provide support for reconstructing the tree structure "on-the-fly" at input. Stream structure is rebuilt from information stored in the file about the number of branches, their type, and the class of objects stored on each branch.(1)
• Requirements for file management:
  • Provide support for n:1 relationships between streams (TTrees) and files, such that multiple streams may be stored in the same file or be spread out over multiple files. (1)
  • Provide access to remote and local files "transparently" (with minimal distinction to user). (1)
  • Provide the ability to open files "on-the-fly" during an analysis or reconstruction job. (2)
    Use Case: User may filter events according to an event summary data stream before deciding to access the full reconstruction data stream, stored in a separate file.

Last modified : Dec 14 2000
Path is http://www.hep.umn.edu/~schubert/persistency/packrat/per_packrat.html