CdmCL Language - Syntax

Transcription

1 CdmCL Language - Syntax This documents illustrates the language syntax to express constraints September, 2014 Version 1.0 by Ahmed AHMED, Jean Philippe BABAU

2 CdmCL language In the following, the different concepts and syntactical constructs of the CdmCL language are explained. Main Structure Each CdmCL grammar starts with a name of the standard to be written, e.g. OceanSITES. Then, some optional comments can be added using the key symbol -- and proceeding this symbol by comment text enclosed by double quotes. The keyword group gives a name of group constraint such as OceanSITESConstraints. Then, the group constraints are added between two braces { }. These are the minimal requirement to create a CdmCL model. After the group context, named lists of names can be added by the keyword namelist followed by two braces { } that hold the lists definition. Each list has a name followed by two parenthesis including a comma separated list of items (,, ). It should end by a semi colon except for the last one. In the same way, after defining the named list of names, the named lists of values can be declared. The keyword valuelist is followed by two braces { }. Inside these braces, the lists can be declared in the same way for namelist. The figure below illustrates an example. 2

3 In this version, the group is followed by the named lists and finally the value lists. The named lists and value lists cannot be commented. Group context constraints The constraints expressed in the group context are written in the following order. Dimensions constraints Dimensions format Dimensions repetition Global Attributes constraints Global Attributes format constraint Global Attributes repetition constraints Variable constraints Variable format constraint Variable repetition constraints User defined constraints Now the grammar for each constraint category is presented. Dimensions Constraints Dimensions constraints start by the keyword dimensions followed by two open and close braces { }. Inside this braces, a list of dimensions constraints are defined. Each dimension constraint begins by the optional keyword IsMandatory to indicate a mandatory dimension. It is followed by the optional keyword IsUnlimited to indicate an unlimited length dimension. After that, the dimension name must be specified. However, several naming scenarios exists. But for the moment, lets us suppose a single dimension name. After specifying the dimension name, an open parenthesis must be written ( followed by an optional min length of the dimension, a mandatory comma,, an optional max length value and a close parenthesis ). Then, a list of optional comments can be added using -- sign. And finally an optional example can be added using the keyword example followed by the example text as shown below 3

4 Each dimension item end by a semi colon except for the last one. This expression defines the constraints to be applied on a single dimension name. In fact, constraints ca also be applied to dimensions matching a regular expression or a list of dimensions names. The syntax always remain the same, the only part that changes, is the name part. To match with regular expression, a smaller than < symbol followed by a name for the regular expression and the greater than sign > are written. Next the keyword matches followed by the regular expression between double quotes. Finally, the constraints are expressed as explained previously. An example is shown below If the constraint is specified on a list of items. Instead of the dimension name, a smaller than symbol < is used followed by a name for the list and ends with a greater than symbol >. Next, the keyword from is added. Here there are two possibilities, if the list is already added in the namelist, then the keyword namelist followed by the name of the list is added. Otherwise, if the list is not specified in the name list, the items of the list are added directly by the keyword from followed with the keyword names, an open parenthesis, a list of comma separated items and a close parenthesis (,, ). An optional keyword or can be added for the lists. It is only helpful for the mandatory constraints that indicate that one item of the list is only mandatory and not all the items. Note: For all cases, the syntax is summarized as shown in the figure below. As the naming convention used for dimensions is similar to global attributes, variables and attributes, these three scenario will be referred as name in general in the next sections. 4

5 Name format It is used to express format constraints optionally on the names of the dimensions, global attributes, variables and variable attributes. The keyword dimensionformat defines format constraints on the dimension. The format can be specified to match a regular expression by the keyword RegEx followed by the regular expression between parentheses ( ). The example below indicate that the dimensions name are upper case letters only. The dimension format can be specified to be either upper case or lower case. The keyword dimensionformat is followed by the keyword StringFormat and two parenthesis ( ). Inside this parenthesis the string format must be specified either LowerCase or UpperCase. Similarly, the format for the Global Attributes, Variables and Attributes can be defined by replacing the keyword dimensionformat by globalattributesformat, variablesformat and variablesattributeformat respectively. However, the order indicated previously must be respected. Name Repetition The optional repetition constraint assures that the dimensions, variables and attributes name are not repeated. For dimensions name, the keywords NoRepetitionDimensionNames is followed by notrepeated. Similarly, repetition verification for global attributes, variables and attributes can be done by replacing the keyword NoRepetitionDimensionNames by NoRepetitionGlobalAttributeNames, NoRepetitionVariableNames and NoRepetitionVariableAttributeNames respectively. Global Attributes Constraints Global attributes constraints start using the keyword globalattributes followed by two open and close braces { }. Inside this braces, a list of global attributes are defined. Each global attribute should end with a semi colon ; except for the last one. Each global attribute, can begin with the keyword, IsMandatory, followed by a name of the global attribute. After that, a list of data types can be added in a separated list of possible data types between parentheses ( ). Next, a value concept must be added. Value concepts will be introduced later in this section. And finally after the value concept, optional comments and an optional example can be added using the double dash symbol -- and the keyword example respectively as shown in figure 5

6 Different ways exists to express value constraints, according to the following scenarios. The square in blue can be replaced according to one of the following concepts. For all cases to define a value constraint, the keyword value is used. Unique value concept: an equal sign = is followed by a value between double quotes. Regular Expression: the keyword matches, an open parenthesis (, a regular expression to match between two quotes and finally the closing parenthesis ). Range: the keyword in, an open square bracket [, a min value, a comma, a max value and finally a close square bracket ]. List: the keyword in valuelist, a name of a predefined value list. Standard: the keyword isstandarizedby, and the name of predefined Standard between two parentheses. If no value constraint, the keyword AnyValue is used, as shown below Variable Constraints Its constraints start using the keyword variables followed by two open and close braces { }. These two braces include a list of variable constraints that end by a semi colon except for the last one. Each variable constraint begins with the keyword ismandatory, followed by the variable name and a comma separated list of data types between parentheses (,, ). After that, the shapes should be specified. Here, similar shape constraint or predefined list of shapes can be specified. For similar shape constraint, the keyword SimilarDimensionConstraint is added. Otherwise, for a list of predefined sets of shapes, two braces { } are required holding a semi colon separated sets { ; ; }. Each set hold a list of comma separated dimensions defined between two parentheses (,, ). The idea is 6

7 clarified in the example below, the names in the named list named ParameterNames can have the shapes from the list having 2 sets, either TIME, DEPTH or TIME, DEPTH, LONGITUDE, LATITUDE. As the global attributes are defined in the group context, variable attributes can be defined in the variable context. After defining the shapes, variable attributes can be defined by the keyword attributes and two braces { }. Inside these braces, a list of attributes are defined in the same way as the list of global attributes. User defined constraints The user defined list of constraints are defined by the keyword userconstraints followed by two braces { }. Each constraint begins with an open parenthesis (, followed by a constraint title, a comma, a constraint body and a close parenthesis ). Each user constraint should end with a semi colon ; except for the last one. 7