18.104.22.168.3 Temporal data completeness constraints
A temporal data completeness constraint needs that the time periods specified in a collection of documents be contiguous and also between them totally span some various other time period: for example,R375.
You are watching: The completeness constraint can be partial or total.
within the employed staff period
specified in every employee record
must be within the moment period
specified in precisely one employee grade record
for the same employee.
Rule statements for this type of rule can be produced from the adhering to template:T38.
Each duration term 1>
within the time period term 2>
specified in the subform hatchet 1> (if any)
must be within the time period term 3>
specified for the subform ax 2>
Much the very same conditions use to the usage of each choice or placeholder as in theme T27 described in section 22.214.171.124.1. In addition note that day is the most common term to be substituted in location of time duration term 1> although any type of term signifying a time duration may be supplied as required.
The adhering to fact varieties should be present in the fact model (either explicitly stated, or acquired as defined in ar 6.3.3 in chapter 6):1.
fact species of the form
‘time period term 1> is within time duration term 2>’, and
‘time period term 1> is within time period term 3>’: because that example, F297 and F299;2.
if subform term 1> is not included, a fact form of the form
‘ specifies time duration term 2>’: because that example, F298;3.
if subform hatchet 1> is included, a fact kind of the form
‘ specifies time period term 2>
for subform hatchet 1>’;4.
if subform ax 2> is no included, a fact kind of the form
‘ specifies time period term 3>’: because that example, F300;5.
if subform term 2> is included, a fact form of the form
‘ specifies time period term 3>
for subform hatchet 2>’;6.
at least one fact type for every qualifying clause (if any), including any type of within either transaction signifier, as described in ar 7.4.1 in thing 7: because that example, F301;7.
at least one fact type for the conditional clause (if any), as also described in section 7.4.1.F297.
day is within employed periodF298.
employee document specifies employed staff periodF299.
day is within time periodF300.
employee grade record specifies time periodF301.
employee grade document is for employee
Thom Frühwirth, ... Christian Schulte, in structures of man-made Intelligence, 2006
13.3.2 Constraint Solvers
We introduce some constraint solvers written in CHR, for details and more solvers see <38, 42>. We will usage the concrete ASCII syntax the CHR implementations in Prolog: conjunction ∧ is composed as comma ‘,’. Disjunction ∨ is composed as semi-colon ‘;’. Let ‘=Boolean constraint solver
Boolean algebra (propositional logic) constraints have the right to be resolved by different techniques <68>. The reasonable connectives are stood for as Boolean constraints, i.e., in relational form. Because that example, conjunction is composed as the constraint and (X, Y, Z), whereby Z is the result of anding X and Y. In the complying with terminating and also confluent Boolean constraint solver <42>, a regional consistency algorithm is used. It simplifies one Boolean constraint at a time right into one or much more syntactic equalities whenever possible. The rules for propositional conjunction space as follows.
The over rules are based upon the idea that, offered a worth for one of the variables in a constraint, we shot to determine values for various other variables. However, the Boolean solver goes past propagating values, due to the fact that it likewise propagates equalities between variables. Because that example, and also (1, Y, Z), neg (Y, Z) will alleviate to false, and also this cannot be completed by value propagation alone.Search.
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The above solver is incomplete. Because that example, the solver can not detect inconsistency of and also (X, Y, Z), and (X, Y, W), neg (Z, W). For completeness, constraint solving needs to be interleaved v search. For Boolean constraints, search deserve to be excellent by do the efforts the values 0 or 1 because that a variable. The generic labeling procedure enum traverses a perform of variables.