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LocalParameter_t Class Reference

Detailed Description

Implementation of SBML Level 3's LocalParameter construct.

LocalParameter has been introduced in SBML Level 3 to serve as the object class for parameter definitions that are intended to be local to a Reaction. Objects of class LocalParameter never appear at the Model level; they are always contained within ListOfLocalParameters lists which are in turn contained within KineticLaw objects.

Like its global Parameter counterpart, the LocalParameter object class is used to define a symbol associated with a value; this symbol can then be used in a model's mathematical formulas (and specifically, for LocalParameter, reaction rate formulas). Unlike Parameter, the LocalParameter class does not have a "constant" attribute: local parameters within reactions are always constant.

LocalParameter has one required attribute, "id", to give the parameter a unique identifier by which other parts of an SBML model definition can refer to it. A parameter can also have an optional "name" attribute of type string. Identifiers and names must be used according to the guidelines described in the SBML specifications.

The optional attribute "value" determines the value (of type double) assigned to the parameter. A missing value for "value" implies that the value either is unknown, or to be obtained from an external source, or determined by an initial assignment. The unit of measurement associated with the value of the parameter can be specified using the optional attribute "units". Here we only mention briefly some notable points about the possible unit choices, but readers are urged to consult the SBML specification documents for more information:

  • In SBML Level 3, there are no constraints on the units that can be assigned to parameters in a model; there are also no units to inherit from the enclosing Model object.

  • In SBML Level 2, the value assigned to the parameter's "units" attribute must be chosen from one of the following possibilities: one of the base unit identifiers defined in SBML; one of the built-in unit identifiers "substance", "time", "volume", "area" or "length"; or the identifier of a new unit defined in the list of unit definitions in the enclosing Model structure. There are no constraints on the units that can be chosen from these sets. There are no default units for local parameters.

As with all other major SBML components, LocalParameter is derived from SBase, and the methods defined on SBase are available on LocalParameter.

Warning
LibSBML derives LocalParameter from Parameter; however, this does not precisely match the object hierarchy defined by SBML Level 3, where LocalParameter is derived directly from SBase and not Parameter. We believe this arrangement makes it easier for libSBML users to program applications that work with both SBML Level 2 and SBML Level 3, but programmers should also keep in mind this difference exists. A side-effect of libSBML's scheme is that certain methods on LocalParameter that are inherited from Parameter do not actually have relevance to LocalParameter objects. An example of this is the methods pertaining to Parameter's attribute "constant" (i.e., isSetConstant(), setConstant(), and getConstant()).
See Also
ListOfLocalParameters
KineticLaw