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SEMI E125-0305 © SEMI 2003, 2005 18 10.4.11 Classifying Parameters Parameter isTransient ParameterClassification ReadWrite ReadOnly Configuration Control classification 1 1 affectedParameters 1 0..* Data AssociatedParame…

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10.4.9 Constraint Definition
10.4.9.1 Parameter constraints describe restrictions on the valid values of Parameters. A constraint is documented
as a propositional formula, which evaluates TRUE with valid parameter values. Relational algebra defines a rich
syntax for propositional formulas; however, this syntax is not commonly used for commercial applications.
Standard Query Language (SQL) is a well-documented commercial application of relational algebra well suited to
this application. Specifically, the syntax of the WHERE clause (of the SQL SELECT statement) is suitable for
describing constraints on Parameter values. The WHERE clause of the SQL SELECT statement is a propositional-
expression that consists of one or more comparisons of values with constants. It has the following form.
WHERE propositional-expression [nested-propositional-expression];
For the purposes of this specification, a subset of the SQL WHERE syntax (the complete syntax is discussed in
Related Information, Section R2-1) shall be used to define constraints. Specifically, the IN, BETWEEN, and IS
operators are not supported in constraint definitions.
10.4.9.2 For example, a Parameter named “TemperatureSetpoint” that represents a temperature set point that may
not be less than 100 or greater than 200 may be described using the following SQL WHERE clause.
WHERE TemperatureSetpoint > 100 AND TemperatureSetpoint < 200;
10.4.9.3 Describing Reporting Frequency Constraints
10.4.9.3.1 To describe the rates at which a given Parameter can be reported for data acquisition, a specific
convention using the subset of the SQL WHERE clause described in Section 10.4.9.1 shall be used. For Parameters
where this is a consideration, a constraint must be provided named “ReportingPeriod”. The definition of the
ReportingPeriod constraint shall take the following form:
WHERE parameterName.ReportingPeriod comparison;
10.4.9.3.2 Here, parameterName is the name of the Parameter to which the constraint applies, and comparison is
any legal combination of terms, operators, or constants necessary to describe the constraint on valid reporting
periods for the Parameter. The time division for any constants that refer to the reporting period shall be in seconds.
If the constraint definition is used to express an integer multiple of a fundamental reporting period, the variable ‘n’
shall be used to represent the multiplier.
10.4.9.3.3 For example, the constraint definition below specifies that the supported reporting period for
“Temperature” is any continuous value between 0.01 seconds and 60 seconds. Additional examples are provided in
Related Information, Section R4-1.
WHERE Temperature.ReportingPeriod >.01 AND Temperature.ReportingPeriod < 60;
10.4.10 Describing SEMI Standard Variables and/or Attributes
10.4.10.1 If the supplier is using a Parameter to represent variables or attributes that have been defined in a SEMI
standard, the name attribute of the Parameter class shall be equal to the name of the variable or attribute exactly as it
is spelled, using the same case convention as found in the corresponding standard. The type mapping described in
Section 10.5.4 shall determine the type assigned to the Parameter.
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10.4.11 Classifying Parameters
Parameter
isTransient
ParameterClassification
ReadWrite ReadOnly
Configuration
Control
classification1
1
affectedParameters
1
0..*
Data
AssociatedParameter
1
associatedParameters0..*
Figure 10
Parameter Classifications
10.4.11.1 Figure 10 shows the classification scheme used to describe the characteristics of a Parameter. There are
two primary classifications, read-only and read-write, that specify whether or not the parameter’s value can be set by
an external entity. If read-only, the Parameter is classified as data. If read-write, there are several subclasses that
can be used to further refine the description of the Parameter’s function.
10.4.11.2 ParameterClassification — This class is the abstract base class for all Parameter classifications.
10.4.11.3 ParameterClassification Attribute Definition Table
Table 28 ParameterClassification Attribute Definition
Attribute Name Definition Form
isTransient Whether or not the Parameter’s value is only
accessible or meaningful under certain
conditions.
Boolean. See Section 10.4.11.3.1.
10.4.11.3.1 isTransient
10.4.11.3.1.1 If false, the Parameter’s value is guaranteed to be accessible and meaningful at all times that the
equipment is available and in a state in which it is possible to communicate with external entities. Parameters that
correspond to SEMI E30 equipment constants and status variables, for example, are non-transient.
10.4.11.3.1.2 If true, the Parameter is said to be “transient”. The value of a transient Parameter is not guaranteed to
be accessible or meaningful except under certain conditions. For example, Parameters that correspond to SEMI E30
“data values” are transient. Additionally, a Parameter may represent an attribute of a transient SEMI E39 ObjType,
in which case its accessibility is determined by the lifecycle of the ObjType. The Parameter may provide data that is
only available when the equipment (or SEMI E39 ObjType) is in a specific state or states. If a transient Parameter is
available for reporting with a specific event, its value may only be meaningful while the equipment is in the target
state for which the event was reported. Or, the Parameter’s value may only be meaningful at the time the event
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occurs. Providing a mechanism to describe the lifecycle for transient Parameters using metadata is beyond the scope
of this specification.
10.4.11.4 ReadWrite — This abstract class identifies a Parameter as being settable by an external entity. The
settings for such Parameters may influence the values or dynamics of other Parameters. For example, Parameters
corresponding to E30 “equipment constants” may be set by an external entity, and so would be classified as
ReadWrite. Parameters corresponding to E30 “status variables” or “data values” cannot be set by external entities,
so would not be classified as ReadWrite.
10.4.11.5 ReadWrite Association Definition Table
Table 29 ReadWrite Association Definition
Association Role Name Definition Comments
affectedParameters A list of associated Parameters that are affected
by the settings of this Parameter.
Unordered list of structured data, of type
AssociatedParameter.
10.4.11.5.1 affectedParameters
10.4.11.5.1.1 If the Parameter’s settings directly affect the values or dynamics of other Parameters elsewhere in the
metadata, an AssociatedParameter instance must be provided and described for each such relationship for the
Parameter being defined. Other generic associations may exist for the Parameter, but the specific associations that
arise from the settings of the Parameter’s value must be accessible through the affectedParameters association
provided by this base class unless otherwise specified in this document.
10.4.11.6 ReadOnly — This abstract class identifies a Parameter as being un-settable by an external entity. Its
value, however, is accessible to external entities. This class has no attributes or associations. For example,
Parameters corresponding to E30 “status variables” or “data values” cannot be set by an external entity, and so
would be classified as ReadOnly. Parameters corresponding to E30 “equipment constants” can be set by external
entities, so could not be classified as ReadOnly.
10.4.11.7 Data — This class is derived from ReadOnly, and identifies a Parameter as providing data values. If non-
transient, (for example, Parameters corresponding to E30 “status values”), the data values are accessible and
meaningful at all times. If transient, (for example, Parameters corresponding to E30 “data values”), the data values
are not guaranteed to be meaningful except when they are explicitly provided with the occurrence of specific events
or, if they represent attributes of an SEMI E39 ObjType, when the corresponding ObjType has at least one active
instance. This class defines no attributes or associations.
10.4.11.8 Control — This is derived from ReadWrite, and identifies a Parameter as being settable by an external
entity (for example, Parameters corresponding to recipe settings). Changes in the values of a Control Parameter
affect the way in which the equipment processes, measures, or tests material and may affect the values of other
Parameters. This class defines no attributes or associations.
10.4.11.8.1 If other Parameters are affected by this Parameter’s settings, all such affected Parameters shall have a
corresponding AssociatedParameter instance provided with the Control Parameter’s definition. Each such
AssociatedParameter instance shall be accessible via the “affectedParameters” association of this class (inherited
from ReadWrite).
10.4.11.8.2 If non-transient, the values of this Parameter are accessible and meaningful at all times, and can be set
by an external entity under conditions determined by the equipment.
10.4.11.8.3 If transient, the values of this Parameter are not guaranteed to be meaningful or settable at all times. If
the Parameter represents an attribute of an SEMI E39 ObjType, the Parameter will only be settable when the
corresponding ObjType has at least one active instance.
10.4.11.9 Configuration — This class is derived from ReadWrite, and identifies a Parameter as being settable by an
external entity, and in some way influencing equipment behavior and/or the values of other Parameters, but is not
considered a control Parameter (for example, E30 “equipment constants” used for configuring equipment
communication timeouts, etc.). This class defines no attributes or associations.