---
path: "absolute-sev"
date: 2021-03-27
title: "Absolute Site Event Score"
hidden: true
---

Given a Site Event (SEV) number `USERS.CLIENTS.INTERNAL`, the number:

1. `USERS` is defined as the _per deci_ of users affected.
2. `CLIENTS` is defined as the _per deci_ of clients affected.
3. `INTERNAL` is defined as the _per deci_ of the internal system affected.

Where _per deci_ is defined as a percent divided by ten and rounded up.
Additional labels for noteworthy "named" events are available as extensions to
the `USERS.CLIENT.INTERNAL` format.

## Introduction

explain problem here.

As a solution to this problem, I propose a similar set of rules heavily inspired
by the [Semantic Versioning 2.0.0] document. Engineers and administration may
use this number as way to signal and convey priority and importance to each
event without necessarily knowing the specifics of each event. This permits
ordering for review and provides a short-code for engineers to quickly
acknowledge the scope of the situation.

This system, despite being closely modeled after Semver, intends to provide an
absolute metric to compare site events, regardless of scale of the site. As a
result, I call this system "Absolute SEV Score".

[Semantic Versioning 2.0.0]: https://semver.org/spec/v2.0.0.HTML

## Absolute Site Event Score (ASEV)

The key words `MUST`, `MUST NOT`, `REQUIRED`, `SHALL`, `SHALL NOT`, `SHOULD`,
`SHOULD NOT`, `RECOMMENDED`, `MAY`, and `OPTIONAL` in this document are to be
interpreted as described in [RFC 2119].

The term _per deci_ is defined as the percent of the affected element divided by
ten and rounded to the nearest integer. For example, if 1%, 3.643%, 10%, and
so forth of users are affected, then the _per deci_ value is defined as 1. If
50.000001% of internal systems are affected, then the _per deci_ value is 6.

1. A normal ASEV number `MUST` take the form A.B.C, where A, B, and C are in
either in the range of 0-10, inclusive and `MUST` NOT contain leading zeros, or
of the values `U`, `IP`, or `X`. A is the `USERS` number, B is the `CLIENTS`
number, and C is the `INTERNAL` number.
2. The `USERS` number `MUST` represent the _per deci_ of people (e.g. end users)
affected by the ASEV.
3. The `CLIENTS` number `MUST` represent the _per deci_ of clients that this
ASEV affects. This value `MUST` be defined as an unweighted total _per deci_ of
clients affected.
4. The `INTERNAL` number `MUST` represent the _per deci_ of internal systems
that this ASEV affects. The value `MUST` be defined as an unweighted total
_per deci_ of internal systems affected.
5. Elements with the value `U` `MUST` transition to the value `IP`, `X`, or a
numeric value. Elements with the value `IP` `MUST` transition to the value `X`
or a numeric value. Numeric values `SHOULD` represent the live _per deci_ value
of the target affected. It is `RECOMMENDED` that an additional ASEV number be
kept that the maximum numeric values of every element is recorded.
6. Elements with the value `U`, `IP`, and `X` represent the state of "Unknown",
"In Progress", and "No data", respectively. These values denote that the true
impact of the ASEV has not been evaluated yet, or in the case of `X`, cannot be
evaluted.
7. ASEV numbers `MAY` be marked with a label by appending a hyphen and a series
of dot separated identifiers following the `INTERNAL` number. Identifiers `MUST`
comprise only ASCII alphanumerics and hyphens `[0-9A-Za-z-]`. Identifiers
`MUST NOT` be empty. Numeric identifiers `MAY` include leading zeros. It is
`RECOMMENDED` to give high impact ASEVs. It is `RECOMMENDED` to have a unique
identifier as a machine identification string. Examples: `3.2.5-spinlock.2314`,
`5.3.9-4.20.2021`, `5.4.3-911-called.4fajh5z`.
8. ASEV numbers in the format `A.B.C-name.id` are in "Named Normal form"
and numbers in the format `A.B.C-id` are known in "Normal form" if the `id`
identifier is unique within the organization, and all ASEV values within the
organization are in either Named Normal or Normal form. It is `RECOMMENDED`
organizations use a combination of Named Normal or Normal form ASEV numbers.
9. The precedence order for element values are as followed: `X`, `IP`, `U`, and
followed by 10 to 0, and is determined by the first left-to-right difference.
It is `RECOMMENDED` that if all ASEVs are in either Normal or in Named Normal
forms that Named Normal numbers have precedence over Normal numbers.


[RFC 2119]: https://tools.ietf.org/html/rfc2119

## Backus-Naur Form Grammer for Valid Absolute Site Event Scores

todo

## Why use Absolute Site Event Scores?

#### Why can any value decrease over time?

The ASEV value is intended to represent the impact of a dynamically changing
situation. Values

#### Why can't a numerical value return to an alphabetical value?

The alphabetical values are to convey the ability to monitor the situation.
During a site event, new events with unknown impact may be denoted as `U.U.U`,
indicating that personnel are needed to evaluate the situation. Likewise, an
`X.X.X` score represents an event with no way to measure the impact. Once these
values can be measured, they should be promoted to values that represent the
estimated impact. If a metric was incorrect, then the value can be reflected
with the new value.

#### Why do alphabetical values have higher values over numbered values?

The inability to measure impact in due time or at all is a serious concern for
long term stability of a service or platform. As a result, these values take
higher precedence than other events with known measured values for two reasons.
One, it is possible that the impact may be as severe or more severe than
previous cases, so it is best to perform analysis as soon as possible. Two, the
inability to detect and measure this data implies a systematic failure to
prevent this incident from occurring in the future.

## License

[Creative Commons—CC BY 3.0](https://creativecommons.org/licenses/by/3.0/)
