A game system's "syntactic elements" are defined as the parts of a game that give it a structure and define the "grammar" by which the game is played. The type of randomizer used, for instance, is a syntactic element. The System X Specification deals mostly with syntactic elements at varying degrees of detail. The "semantic elements" are the parts of a game that define specific elements of the universe and provide the "vocabulary" of the game. The specific names of skill value components, or the particular abilities of characters, are examples of semantic elements.
Rules in System X are divided into three categories. The first category is the core resolution mechanic rules, which provide the basic means by which success or failure are determined. The core resolution mechanic is designed to be setting-independent. The second category is the interpretation rules, which use the degree of success of failure to determine whether or not an abstract task is successful. Interpretation rules may be, but are not necessary, setting-independent. The final category is the world rules, which provide setting-dependent interpretations and descriptions for particular tasks. Collectively, the interpretation and world rules are generally considered to be "game semantics."
Three terms are used in this manual to define particular degrees of compliancy to the Reference Manual. They are:
Uses System X – A game is defined as using System X (and is therefore eligible to use the trademark "Uses System X") if it implements at least the basic randomizer syntax, also known as the core resolution mechanic.
System X compatible – A game is defined as being System X compatible (and is therefore eligible to use that trademark) if it implements the basic randomizer syntax as well as the syntactic elements of Attributes and Skills.
System X compliant – A game is defined as being System X compliant (and is therefore eligible to use that trademark) if it implements all requirements stated in this Manual.
By default, any game that is System X compatible or System X compliant must implement all aspects of a game that Uses System X. A game that is System X compliant must also implement all aspects of a game that is System X compatible.
Games that use the above trademarks to claim a degree of compliancy to the specification must also state to which version(s) of the specification they are compliant. Such games must state at least the most recent version of the specification to which they are compliant, and may list all versions of the specification to which they are compliant. Games may also list any sources that have independently judged the game's level of compliance, but if they do so, they must list the judgments in a clear, unambiguous fashion complete with the date and place of publication (if any) of the judgment.
The terms "must" and "required" are used to denote a particular requirement that must be satisfied by a game at a particular degree of compliancy. A failure to satisfy the requirement prevents certification of the game at that degree of compliancy. The terms "may" and "optional" are used to denote a particular requirement that may be satisfied by a game at a particular degree of compliancy; failure to satisfy the requirement does not prevent certification of the game at that degree of compliancy. Many "optional" requirements are "recommended;" such requirements still need not be satisfied, but for various reasons, it is strongly suggested that they be satisfied.
Any possible rule that is not discussed is considered to be ignored by this specification and may be placed legitimately in any System X game. By default, anything not restricted or otherwise defined is permitted.
This specification only addresses tabletop rules. LARP rules may be addressed in a future version of this specification or in another, related specification.