The BABAR Event Query Tag User's Guide
Version Information
Draft: 15th June 1998
This document is still under development. If you have any questions or comments, please address them to the author.
The BABAR Event Query Tag is a mechanism for rapid selection of events having
desirable characteristics from an input event collection. It allows an output collection to be created that contains just those events of interest from an input collection.
Note that the event selection tag is likely to be redesigned following Mock Data Challenge II (MDC-II) and this document describes only the tag and acess for the tag for MDC-II.
Description
The AbsEventTag class is the abstract transient event query tag.
Inheritance Tree
AbsEventTag
Interface
#include "AbsEventTag/AbsEventTag.hh"
Constructors
None.
Selectors
bool getBool ( bool& value, const char* const key ) = 0
bool getInt ( int& value, const char* const key ) = 0
bool getFloat( float& value, const char* const key ) = 0
Get an attribute of the specified type and having the specified name. The function value indicates whether an attribute exists of the specified type and with the specified name. These functions are abstract.
Modifiers
bool putBool ( bool value, const char* const key ) = 0
bool putInt ( int value, const char* const key ) = 0
bool putFloat( float value, const char* const key ) = 0
Insert an attribute of the specified type and having the specified name into the transient event query tag, replacing any previous value that might have already have been inserted within this type and name. The function
value indicates whether the insertion was successful. These functions are abstract.
Operations
None.
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Description
The TagTransient class is the transient event query tag. It inherits from the AbsEventTag abstract parent class.
Inheritance Tree
TagTransient > AbsEventTag
Interface
#include "TagData/TagTransient.hh"
Constructors
TagTransient( )
Create a transient event query tag.
Selectors
bool getBool ( bool& value, const char* const key )
bool getInt ( int& value, const char* const key )
bool getFloat( float& value, const char* const key )
Get an attribute of the specified type and having the specified name. The function value indicates whether an attribute exists of the specified type and with the specified name.
Modifiers
bool putBool ( bool value, const char* const key )
bool putInt ( int value, const char* const key )
bool putFloat( float value, const char* const key )
Insert an attribute of the specified type and having the specified name into the transient event query tag, replacing any previous value that might have already have been inserted within this type and name. The function
value indicates whether the insertion was successful. A failure indicates that an attribute already exists with the specified name but which has a different type.
Operations
None.
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Description
The BdbEventTag class is the persistent event query tag. The user interface to this class is provided by the TagAttribute<T> templated tag attribute class. The
BdbEventTag class itself is described in the BABAR Event Store Reference Manual.
Return to Table of Contents.
Description
The templated TagAttribute<T> class provides the primary user interface to the persistent event query tag. Instances of such templated attributes may be created and bound via a
TagAttributeManager object. Thereafter they may be treated as variables of conventional basic data types. A suitable TagAttributeManager object is provided by the TagFastFilterModule
framework module.
Inheritance Tree
TagAttribute<T> > TagAttributeBase
Interface
#include "TagDataP/TagAttribute.hh"
Constructors
TagAttribute( const char* const theName, TagAttributeManager& theManager )
Create a templated.
Selectors
None.
Modifiers
None.
Operations
None.
Operators
const TagAttribute<T>& operator = ( T value )
const TagAttribute<T>& operator = ( const TagAttribute<T>& theOther )
Assign a value to the tag attribute.
operator T( ) const
Return tag attribute value.
Return to Table of Contents.
The following BABAR software packages contain classes that manage the event
query tag.
- BdbEvent. This package contains the persistent event query tag class.
- TagData. This package contains the transient event query class.
- TagDataP. This package contains the tag attribute classes and converters classes etc.
- TagModules. This package contains framework modules that create, fill or perform event selections based on the event query tag.
The following modules deal with the event query tag within the BABAR
Framework.
- TagBdbLoad. This module performs reading and writing to the event store. In the case of reading, it creates the transient event query tag from the persistent one, and in the case of writing it
creates the persistent event query tag from the transient one.
- TagCreateModule. This module creates an empty transient event query tag object and associates it with the transient event.
- TagFillExample. This is an example of a module that locates the transient event query tag within the transient event and fills entries into it.
- TagFilterModule. This is a Framework filter module that is designed to act as a base class for user-level event query tag filter modules. Such modules access the transient tag within the transient
event and perform filtering based on the transient attributes. The FagFilterExample module is an example of such a filter module.
- TagFilterExample. This is an example of a module that locates the transient event query tag within the transient event and filters events having particular characteristics.
- TagFastFilterModule. This is a Framework filter module that is designed to act as a base class for user-level fast filter modules. Such modules declare templated tag attributes that bind to the
underlying persistent event query tag and perform filtering based on these attribute objects. They therefore have smaller overhead than modules based on the TagFilterModule module. The
TagFastFilterExample module is an example of such a filter module.
- TagFastFilerExample. This is an example of a module that declares several templated tag attributes and filters events having particular characteristics.
Return to Table of Contents
A framework application wishing to create and fill the transient tag, adding this to the information output to the event store after all event processing is completed, must setup a processing path that includes the following
modules:
path create TagPath BdbCreateCM TagBdbLoad TagCreateModule <theTagFillModule>
Although other modules may appear in the processing path, those that that must appear in the specified relative sequence are:
- BdbCreateCM. This module creates the Converter Managers for the event and associates them with the transient event. It is required by all paths that access the event store either for input or
output.
- TagBdbLoad. This module controls whether the event query tag will be read from the event store or written to it. In this case it must appear in order to cause the the tag information to be written
to the event store.
- TagCreateModule. This module creates an empty transient event query tag object and associates it with the transient event so that it is available for downstream modules.
- <theTagFillModule>. This is the module that fills the transient tag. An example of such a module is the TagFillExample module which is used for the remainder of this
example. It should be replaced by the actual desired module.
In order that these modules be linked into the application, the AppUserBuild.cc file should include the following code fragments:
#include "BdbConverters/BdbCreateCM.hh"
#include "TagModules/TagBdbLoad.hh"
#include "TagModules/TagCreateModule.hh"
// Replace the following by the actual module. This is just an example
#include "TagModules/TagFillExample.hh"
[....]
add( new BdbCreateCM ( "BdbCreateCM" , "Create Converter Manager Module" );
add( new TagBdbLoad ( "TagBdbLoad" , "Tag Loader Module" );
add( new TagCreateModule( "TagCreateModule", "Tag Creator Module" );
// Replace the following by the actual tag filling module.
add( new TagFillExample ( "TagFillExample" , "Tag Fill Example Module" );
In order for the tag information to be written to the event store along with any other event-related information, the TagBdbLoad module must be setup to output the information by using the following
Tcl fragment:
module talk TagBdbLoad
writeTag set true
exit
The relevant code fragments from the TagFillExample module code that locates the transient tag within the transient event, and creates some transient attributes is:
TagFillExample.cc
#include "AbsEventTag/AbsEventTag.hh"
[....]
AbsEvent*
TagFillExample::event( AbsEvent* ev, int mode )
{
bool status;
AbsEventTag* theTag = Ifd<AbsEventTag>::get( ev );
if ( 0 != theTag ) {
status = theTag->putBool ( true, "aBoolValue" );
assert( status );
thetag->putInt ( 10, "anIntValue" );
theTag->putFloat( 100.0, "aFloatValue" );
[....]
}
return ev;
}
Note that the transient event tag is declared to be of type AbsEventTag, the abstract parent class, rather than of type TagTransient.
Return to Table of Contents.
A framework application wishing to input the tag information from the event store and filter based on tag attribute values, must setup a processing path that includes the following modules:
path create TagPath BdbCreateCM TagBdbLoad BdbEventUpdate <theTagFilterModule>
Although other modules may appear in the processing path, those that that must appear in the specified relative sequence are:
- BdbCreateCM. This module creates the Converter Managers for the event and associates them with the transient event. It is required by all paths that access the event store either for input or
output.
- TagBdbLoad. This module controls whether the event query tag will be read from the event store or written to it. In this case it must appear in order to cause the the tag information to be written
to the event store.
- BdbEventUpdate. This module actually performs the input of information from the event store based on prior setting of the various loader modules (in this case just
TagBdbLoad) that appear upstream in the path..
- <theTagFilterExample>. This is the module that locates the transient tag and filters using it. It must inherit from the TagFilterModule class. An example of such a
module is the TagFilterExample module which is used for the remainder of this example. It should be replaced by the actual desired module.
In order that these modules be linked into the application, the AppUserBuild.cc file should include the following code fragments:
#include "BdbConverters/BdbCreateCM.hh"
#include "TagConverters/BdbEventUpdate.hh"
#include "TagModules/TagBdbLoad.hh"
// Replace the following by the actual module. This is just an example
#include "TagModules/TagFilterExample.hh"
[....]
add( new BdbCreateCM ( "BdbCreateCM" , "Create Converter Manager Module" );
add( new BdbEventUpdate ( "BdbEventUpdate" , "Event Store Update Module" );
add( new TagBdbLoad ( "TagBdbLoad" , "Tag Loader Module" );
// Replace the following by the actual tag filtering module.
add( new TagFilterExample( "TagFilterExample", "Tag Filter Example Module" );
In order for the tag information to be read to the event store along with any other event-related information, the TagBdbLoad module must be setup to input the information by using the following Tcl
fragment:
module talk TagBdbLoad
readTag set true
exit
The relevant code fragments from the TagFilterExample module code that locates the transient tag within the transient event, and creates some transient attributes is:
TagFilterExample.hh
#include "TagModules/TagFilterModule.hh"
[....]
class TagFilterExample : public TagFilterModule {
[....]
};
TagFilterExample.cc
#include "TagModules/TagFilterExample.hh"
#include "AbsEventTag/AbsEventTag.hh"
[....]
AbsEvent*
TagFilterExample::event( AnsEvent* ev, int mode )
{
bool aBool;
float aFloat;
int anInt;
bool status;
bool passed = false;
TagFilterModule::event( ev, mode );
if ( 0 != tag( ) ) {
status = tag( )->getBool ( aBool, "aBoolValue" );
status = tag( )->getInt ( anInt, "anIntValue" );
status = tag( )->getFloat( aFloat, "aFloatValue" );
[....]
// Decide whether this event passes the event selection criteria
passed = true;
}
[....]
// Mark the event for further processing depending on the "passed" flag
setPassed( passed );
return ev;
}
Note that the transient event tag is declared to be of type AbsEventTag, the abstract parent class, rather than of type TagTransient.
Return to Table of Contents.
A framework application wishing to input the tag information from the event store and perform fast filtering filter based on templated tag attribute values, must setup a processing path that includes the following
modules:
path create TagPath <theTagFastFilterModule>
Although other modules may appear in the processing path, those that that must appear in the specified relative sequence are:
- <theTagFastFilterExample>. This is the module that declares templated tag attributes and binds them using a TagAttributeManager object. It must inherit from the
TagFastFilterModule class. An example of such a module is the TagFastFilterExample module which is used for the remainder of this example. It should be replaced by the actual desired module.
In order that these modules be linked into the application, the AppUserBuild.cc file should include the following code fragments:
// Replace the following by the actual module. This is just an example
#include "TagModules/TagFastFilterExample.hh"
[....]
// Replace the following by the actual tag fast filtering module.
add( new TagFastFilterExample( "TagFast FilterExample", "Tag Fast Filter Example Module" );
The relevant code fragments from the TagFastFilterExample module code that declares templated tag attributes and binds them using a TagAttributeManager object
is:
TagFastFilterExample.hh
#include "TagModules/TagFastFilterModule.hh"
[....]
class TagFastFilterExample : public TagFastFilterModule {
[....]
private:
// Declare several templated tag attributes
TagAttribute<bool> _aBool;
TagAttribute<float> _aFloat;
TagAttribute<int> _anInt;
};
TagFastFilterExample.cc
#include "TagModules/TagFastFilterExample.hh"
[....]
// Constructor
TagFastFilterExample::TagFastFilterExample( const char* const theName,
const char* const theDescription )
: TagFastFilterModule( theName, the Description ),
// Name and bind the tag attributes to the tag manager
_aBool ( "aBoolValue" , _tagManager ),
_aFloat( "aFloatValue", _tagManager ),
_anInt ( "anIntValue" , _tagManager )
{
}
[....]
AbsEvent*
TagFastFilterExample::event( AnsEvent* ev, int mode )
{
bool aBool;
float aFloat;
int anInt;
bool status;
bool passed = false;
// Setup for this event
if ( setup( ev ) ) {
// Access tag information
if ( _aBool ) {
[....]
}
float myData = 10.0 * _aFloat;
[....]
// Decide whether this event passes the event selection criteria
passed = true;
}
[....]
// Mark the event for further processing depending on the "passed" flag
setPassed( passed );
return ev;
}
Note that the transient event tag is declared to be of type AbsEventTag, the abstract parent class, rather than of type TagTransient.
Return to Table of Contents.
References
None.
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