siena::Constraint Class Reference

interface of a generic constraint in the attribute-based data model. More...

#include <attributes.h>

Inheritance diagram for siena::Constraint:

Collaboration diagram for siena::Constraint:

Public Member Functions
virtual	~Constraint ()
	virtual destructor
virtual OperatorId	op () const =0
	returns the operator defined for this constraint.
virtual bool	covers (const Attribute &a) const
	applies this constraint to an attribute. More...
Public Member Functions inherited from siena::Attribute
virtual	~Attribute ()
	virtual destructor
virtual String	name () const =0
	returns the name of this attribute.
Public Member Functions inherited from siena::Value
virtual	~Value ()
	virtual destructor
virtual TypeId	type () const =0
	returns the actual type of this value.
virtual Int	int_value () const =0
	returns this value as an integer. More...
virtual String	string_value () const =0
	returns this value as a string. More...
virtual Bool	bool_value () const =0
	returns this value as a boolean. More...
virtual Double	double_value () const =0
	returns this value as a double. More...

Detailed Description

interface of a generic constraint in the attribute-based data model.

A constraint is defined by a name, an operator, and a value. A constraint expresses the condition that must be matched by a message. Specifically, a constraint defined by name N, operator Op, and value V is matched by a message M if M contains an attribute named N and value X and any of the following conditions applies:

1. Op == ANY and V.type() == ANYTYPE

2. Op == ANY and V.type() == X.type()

3. value X and value V (in this order) are in the relation defined by operator Op. In general, this happens in the following cases:

   • same type, matching values: X.type() == V.type() and the two values satisfy the semantics of the Op condition as defined intuitively. For example, if Op is LT and X.type() == V.type() == STRING, then the constraint is satisfied if X.string_value() is less than V.string_value(), which means that X.string_value() precedes V.string_value() in lexicographical order.

   • compatible types, matching values: X.type() == INT and V.type() == DOUBLE (or vice versa) and X.int_value() Op V.double_value().

   Notice that some operators are type-specific (e.g., SF, PF, SS are defined for strings only).

See Also

OperatorId, Attribute, Value

Member Function Documentation

virtual bool siena::Constraint::covers ( const Attribute &  a) const

virtual

applies this constraint to an attribute.

Returns

true iff this constraint matches (i.e., covers) the given attribute.