Abstract Syntax Tree
The DSL compiles into an abstract syntax tree describing the following:
Periodic Vesting Cadence
The fundamental component of a vesting schedule is a periodic sequence of vesting installments. This periodic sequence one is described by a number of installments and the duration of the step between each installment.
The duration of the step between each installment is given by EVERY <duration> in the grammar.
In order to target natural language in the DSL, we derive the number of installments from the overall length of the periodic sequence, which is given by OVER <duration> in the grammar.
The grammar enforces that OVER and EVERY appear together. Neither can be provided without the other. If both are omitted, a duration of 0 days with 1 occurrence is injected, indicating automatic vesting on the resolved vesting start date.
Years are converted to months and weeks are converted to days in the normalized AST. OVER and EVERY must have the same base unit (months or days).
Example: Periodic Vesting Cadence With Year -> Month Conversion
DSL
VEST
OVER 48 months EVERY 1 months
AST
{
"expr": {
"periodicity": {
"type": "MONTHS",
"length": 1,
"occurrences": 48
}
}
}
Example: Omitted OVER/EVERY
DSL
VEST
AST
{
"expr": {
"periodicity": {
"type": "DAYS",
"length": 0,
"occurrences": 1
}
}
}
Vesting start
Each periodic sequence of vesting installments requires a vesting start date from which to calculate the series of installments.
The vesting-start is given by FROM <vesting-expr> in the grammar. The vesting start may be omitted, in which case it is assumed to be the grant date of the security.
EVENT vestingStart is a system event that is derived during the normalization process. This is necessary so that the cliff can refer back to the resolved vesting start.
However, this means that EVENT vestingStart may not be used in the FROM <vesting-expr, and doing so will throw an error.
Example: Omitted Vesting Start
DSL
VEST
AST
{
"expr": {
"type": "SINGLETON",
"vesting_start": {
"type": "SINGLETON",
"base": {
"type": "EVENT",
"value": "grantDate"
},
"offsets": []
},
"periodicity": {
"type": "DAYS",
"length": 0,
"occurrences": 1
}
}
}
Example: Vesting Start with Event
DSL
VEST FROM EVENT milestone
AST
{
"expr": {
"type": "SINGLETON",
"vesting_start": {
"type": "SINGLETON",
"base": {
"type": "EVENT",
"value": "milestone"
},
"offsets": []
},
"periodicity": {
"type": "DAYS",
"length": 0,
"occurrences": 1
}
}
}
Cliff accrual
Another common feature of vesting schedules is the concept of a "cliff". When a cliff applies, all vesting installments prior to the cliff are accrued and accumulated until the cliff occurs.
A cliff only applies in the context of a periodic sequence of vesting installments.
By convention, a CLIFF <duration> is understood to refer to the resolved vesting start.
Example: Simple Cliff
DSL
VEST
OVER 48 months EVERY 1 months
CLIFF 12 months
AST
{
"expr": {
"type": "SINGLETON",
"vesting_start": {
"type": "SINGLETON",
"base": {
"type": "EVENT",
"value": "grantDate"
},
"offsets": []
},
"periodicity": {
"type": "MONTHS",
"length": 1,
"occurrences": 48,
"cliff": {
"type": "SINGLETON",
"base": {
"type": "EVENT",
"value": "vestingStart"
},
"offsets": [
{
"type": "DURATION",
"value": 12,
"unit": "MONTHS",
"sign": "PLUS"
}
]
}
}
}
}
Selectors
Selectors select between alternative expressions.
Given the temporal aspect of vesting schedules, a selector can be thought of as either choosing the EARLIER OF or LATER OF given items. In the case of an EARLIER OF selector, the first item to occur is selected. In the case of a LATER OF selector, both items must occur, and the later of the items is selected.
Note that in this way EARLIER OF acts as an OR logical operator and LATER OF acts as an AND logical operator. However, we have purposefully limited ourselves to the EARLIER OF and LATER OF nomenclature in order to distinguish selectors from conditions, described below.
Example: Vesting Start With Selector
DSL
VEST FROM EARLIER OF( DATE 2025-01-01, EVENT milestone )
AST
{
"expr": {
"type": "SINGLETON",
"vesting_start": {
"type": "EARLIER_OF",
"items": [
{
"type": "SINGLETON",
"base": {
"type": "DATE",
"value": "2025-01-01"
},
"offsets": []
},
{
"type": "SINGLETON",
"base": {
"type": "EVENT",
"value": "milestone"
},
"offsets": []
}
]
},
"periodicity": {
"type": "DAYS",
"length": 0,
"occurrences": 1
}
}
}
Selector over schedules
In the case of a selector in FROM <vesting-expr>, the selection is determined based on the resolved vesting start, regardless of the cadence of the vesting installments that folllow
DSL
VEST EARLIER OF(
FROM DATE 2025-01-01
OVER 12 months EVERY 1 months,
FROM DATE 2026-01-01
)
AST
{
"expr": {
"type": "EARLIER_OF",
"items": [
{
"type": "SINGLETON",
"vesting_start": {
"type": "SINGLETON",
"base": {
"type": "DATE",
"value": "2026-01-01"
},
"offsets": []
},
"periodicity": {
"type": "DAYS",
"length": 0,
"occurrences": 1
}
},
{
"type": "SINGLETON",
"vesting_start": {
"type": "SINGLETON",
"base": {
"type": "DATE",
"value": "2025-01-01"
},
"offsets": []
},
"periodicity": {
"type": "MONTHS",
"length": 1,
"occurrences": 12
}
}
]
}
}
Example: Cliff with Selector
DSL
VEST
OVER 48 months EVERY 1 months
CLIFF EARLIER OF(
+12 months,
EVENT ipo
)
AST
{
"expr": {
"type": "SINGLETON",
"vesting_start": {
"type": "SINGLETON",
"base": {
"type": "EVENT",
"value": "grantDate"
},
"offsets": []
},
"periodicity": {
"type": "MONTHS",
"length": 1,
"occurrences": 48,
"cliff": {
"type": "EARLIER_OF",
"items": [
{
"type": "SINGLETON",
"base": {
"type": "EVENT",
"value": "ipo"
},
"offsets": []
},
{
"type": "SINGLETON",
"base": {
"type": "EVENT",
"value": "vestingStart"
},
"offsets": [
{
"type": "DURATION",
"value": 12,
"unit": "MONTHS",
"sign": "PLUS"
}
]
}
]
}
}
}
}
Conditions
Conditons condition one vesting expression on the occurrence of another.
We again leverage the temporal aspect of vesting schedules in order to limit ourselves to BEFORE and AFTER nomenclature. Any condition can optionally utilize the STRICTLY keyword to indicate < or >, respectively.
In addition, conditions can be combined with AND and OR operators. We follow SQL like precedence (AND binds tighter than OR, and parentheses override precedence).
DSL
VEST FROM EVENT milestone
STRICTLY BEFORE DATE 2025-01-01 AND
AFTER EVENT threshold
AST
{
"expr": {
"type": "SINGLETON",
"vesting_start": {
"type": "SINGLETON",
"base": {
"type": "EVENT",
"value": "milestone"
},
"offsets": [],
"constraints": {
"type": "AND",
"items": [
{
"type": "ATOM",
"constraint": {
"type": "BEFORE",
"base": {
"type": "SINGLETON",
"base": {
"type": "DATE",
"value": "2025-01-01"
},
"offsets": []
},
"strict": true
}
},
{
"type": "ATOM",
"constraint": {
"type": "AFTER",
"base": {
"type": "SINGLETON",
"base": {
"type": "EVENT",
"value": "threshold"
},
"offsets": []
},
"strict": false
}
}
]
}
},
"periodicity": {
"type": "DAYS",
"length": 0,
"occurrences": 1
}
}
}
Amounts
In vestlang the thing that the vesting schedule applies to is left ambiguous. For purposes of this documentation we have discussed vesting schedules in terms of equity-based compensation awards, but in practice it could apply to anything.
Amounts specify how much of the grant a statement applies to. Integers imply absolute amounts, decimals in [0, 1] imply a percentage, and fractions imply a portion of total statement amount, supplied downstream. If amount is omitted, the default is 100% (1.0)
Example: Omitted Amount
DSL
VEST
AST
{
"amount": {
"type": "PORTION",
"numerator": 1,
"denominator": 1
}
}
Example: Integer Amount
DSL
100 VEST
AST
{
"amount": {
"type": "QUANTITY",
"value": 100
}
}
Example: Decimal Amount
DSL
0.5 VEST
AST
{
"amount": {
"type": "PORTION",
"numerator": 1,
"denominator": 2
}
}
Example: Fraction Amount
DSL
1/2 VEST
AST
{
"amount": {
"type": "PORTION",
"numerator": 1,
"denominator": 2
}
}
Two-Tier Vesting Example
We can demonstrate the expressiveness of the vestlang DSL and AST by constructing a statement which describes a two-tier vesting schedule.
Two-tier vesting refers to a periodic vesting cadence with a standard time-based cliff, as well as one or more event-based cliffs with expiration dates.
The standard two-tier vesting schedule seen in the wild is a 4-year monthly vesting schedule with a 1-year cliff, as well as a cliff on the earlier of an IPO or change in control, so long as the IPO or change in control occurs on prior to the 7th anniversary of the grant date.
This is expressed in vestlang DSL as follows. Note that the 12 months duration in the cliff statement refers to the resolved vesting start, and we use the EVENT grantDAte system event to provide the expiration dates for the cliffs.
DSL
VEST
OVER 48 months EVERY 1 months
CLIFF LATER OF(
+12 months,
EARLIER OF(
EVENT ipo
BEFORE EVENT grantDate +84 months,
EVENT cic
BEFORE EVENT grantDate +84 months
)
)
AST
{
"expr": {
"type": "SINGLETON",
"vesting_start": {
"type": "SINGLETON",
"base": {
"type": "EVENT",
"value": "grantDate"
},
"offsets": []
},
"periodicity": {
"type": "MONTHS",
"length": 1,
"occurrences": 48,
"cliff": {
"type": "LATER_OF",
"items": [
{
"type": "SINGLETON",
"base": {
"type": "EVENT",
"value": "vestingStart"
},
"offsets": [
{
"type": "DURATION",
"value": 12,
"unit": "MONTHS",
"sign": "PLUS"
}
]
},
{
"type": "EARLIER_OF",
"items": [
{
"type": "SINGLETON",
"base": {
"type": "EVENT",
"value": "CIC"
},
"offsets": [],
"constraints": {
"type": "ATOM",
"constraint": {
"type": "BEFORE",
"base": {
"type": "SINGLETON",
"base": {
"type": "EVENT",
"value": "grantDate"
},
"offsets": [
{
"type": "DURATION",
"value": 84,
"unit": "MONTHS",
"sign": "PLUS"
}
]
},
"strict": false
}
}
},
{
"type": "SINGLETON",
"base": {
"type": "EVENT",
"value": "ipo"
},
"offsets": [],
"constraints": {
"type": "ATOM",
"constraint": {
"type": "BEFORE",
"base": {
"type": "SINGLETON",
"base": {
"type": "EVENT",
"value": "grantDate"
},
"offsets": [
{
"type": "DURATION",
"value": 84,
"unit": "MONTHS",
"sign": "PLUS"
}
]
},
"strict": false
}
}
}
]
}
]
}
}
}
}