JSL Syntax
This section describes the common elements of JSL syntax.
Conventions
The following conventions are used in the syntax description: angle brackets (< and >) indicate variable parts, brackets ([ and ]) indicate optional parts. Vertical lines (|) indicate that you must choose one alternative. Dots (…) mean that the preceding element can be repeated.
All symbols (keywords, parentheses, dots, brackets, etc.) in bold purple must be taken literally.
For example, a simplified version of the well-known copy command looks like this with these conventions.
cp [-a|-l|-r]... <source>... <directory>
Overall structure
Domain models are defined by a sequence of JSL statements. Each domain model is in a text file. The extension of the model text files shall be "jsl". E.g. CRM.jsl file contains the model definition of the customer relationship management (CRM) model.
Domain models may refer to each other. References between models allow to partition domain models into multiple (sub)domains.
Statements
JSL statements are composed from:
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JSL keywords
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Expressions
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Element names (entities, fields, enumerations etc.)
JSL statements are terminated by a semicolon (;). A semicolon is optional at the end of block declarations ({ … }). However, extra ; tokens after statements have no effect.
A statement can be broken into several lines.
The following example is syntactically valid.
Example:
model shop;
type string String min-size:0 max-size:128;
entity Person {
field required String firstName default:"";
field required String lastName default:"";;;;;
field String fullName <=
self.firstName + " " + self.lastName;
};Keywords
Keywords are predefined, reserved words used in JSL that have special meanings in the language. JSL keywords are always lowercase.
Most keywords can also be used as element names. However, there are reserved keywords that cannot be used directly as an element name. If you still want to use these reserved keywords as element names, the words must be enclosed in back-tick (`) characters as shown in the example below.
field String `void`;
This is the list of reserved keywords in the JSL.
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Element names
The names of JSL domain elements must conform to the following rules:
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Names are case-sensitive.
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Name of elements must be unique within their scope in a case-insensitive manner.
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A name can be a sequence of uppercase and lowercase English letters (A-Z, a-z) and digits (0-9).
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The first character of a name must be a letter.
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A name must have at least one character.
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A name must not be longer than 128 characters.
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Even though element names (e.g. entity names, field names, enumeration literals, etc.) are case-sensitive, it is not allowed to have two elements in the same scope (e.g. two fields within an entity) whose names differ only in upper and lower case. |