Modal Forms

Requirements can be written on five modal forms:

shall-form
present tense form
will-form
should-form
must-form

A Requirements Specification can often contain different forms without consideration. It is recommended that only one form is consistently used throughout the whole Specification.

Shall-form not allowed.

The requirement uses the shall-form, which is not allowed according to a rule.

An example of the shall-form is:

The DHCP server shall distribute DHCP addresses to clients in the network.

Present tense form not allowed.

The requirement uses the present tense form, which is not allowed according to a rule.

An example of the present tense is:

The DHCP server distributes DHCP addresses to clients in the network.

Will-form not allowed.

The requirement uses the will-form, which is not allowed according to a rule.

An example of the will-form is:

The DHCP server will distribute DHCP addresses to clients in the network.

Should-form not allowed.

The requirement uses the should-form, which is not allowed according to a rule.

An example of the should-form is:

The DHCP server should distribute DHCP addresses to clients in the network.

Must-form not allowed.

The requirement uses the must-form, which is not allowed according to a rule.

An example of the must-form is:

The DHCP server must distribute DHCP addresses to the clients in the network.

Past tense form not allowed.

The requirement uses the past tense, which is not allowed according to a rule.

An example of the past tense is:

The DHCP server has distributed DHCP addresses to the clients in the network.

Authors cannot select to use the past tense modal form. The past tense modal form will always result in an Issue, unless the Do not check modal rule is activated.

The requirement is not on any allowed forms.

None of the allowed modal forms for writing requirements are used for the particular requirement.