The article in the source (cognitect) is really great. > [!quote] > Agile methods are not opposed to documentation, only to valueless documentation. Documents that assist the team itself can have value, but only if they are kept up to date. Large documents are never kept up to date. Small, modular documents have at least a chance at being updated. > > Nobody ever reads large documents, either. Most developers have been on at least one project where the specification document was larger (in bytes) than the total source code size. Those documents are too large to open, read, or update. Bite sized pieces are easier for for all stakeholders to consume. > > One of the hardest things to track during the life of a project is the motivation behind certain decisions. A new person coming on to a project may be perplexed, baffled, delighted, or infuriated by some past decision. Without understanding the rationale or consequences, this person has only two choices: > > 1. **Blindly accept the decision.** > 2. **Blindly change it.** # Technique The technique is to record in **small, terse documents** [[Atomic Notes]] about each important architectural decision. Using a template to enable [[Standard Processes|standardization]], typically using [[Markdown]], using one file per decision, and co-locating these decisions with your source code in [[Version Control]] in a dedicated folder (e.g. `docs/adrs/`). There is no **one** standard for how to format and build ADRs, many different suggestions are abound. Just pick one and be consistent with it within any one system documentation set. After having done ~half a dozen of them, I've settled on [[My Approach to ADRs]]. Some recommended practices (from sources): - Each ADR is its own file, titled in a numeric incrementally increasing sequence like `adr-001.md` (I would probably also include the title of the decision in the file name), put in a directory like `docs/adrs/`. - If an ADR decision is reversed, it's not deleted. It's `status` is changed to superseded & a link to the new decision is placed there. ## Template(s): Note - later on you made & wrote [[My Approach to ADRs]]. See that. There's the original one, and a new one that looks like it's trying to become "the standard". There is no "the standard", though. Unless you adopt some form of tooling that has a suggested format, just pick one from below and roll with it. ### Originally Discovered Template The "this section describes" text would be replaced with what it describes. ```plaintext # Title These documents have names that are short noun phrases. For example, "ADR 1: Deployment on Ruby on Rails 3.0.10" or "ADR 9: LDAP for Multitenant Integration" ## Context This section describes the forces at play, including technological, political, social, and project local. These forces are probably in tension, and should be called out as such. The language in this section is value-neutral. It is simply describing facts. ## Decision This section describes our response to these forces. It is stated in full sentences, with active voice. "We will …" ## Status A decision may be "proposed" if the project stakeholders haven't agreed with it yet, or "accepted" once it is agreed. If a later ADR changes or reverses a decision, it may be marked as "deprecated" or "superseded" with a reference to its replacement. ## Consequences This section describes the resulting context, after applying the decision. All consequences should be listed here, not just the "positive" ones. A particular decision may have positive, negative, and neutral consequences, but all of them affect the team and project in the future. ``` ### MADR - a newer alternative to the above From the GitHub ADR Organization - looks like they are trying to standardize "MADR" as "Markdown Architectural Decision Record", using a select-your-level-of-detail set of templates. This is a medium-sized version of their suggested template. There's a [full-blown version](https://raw.githubusercontent.com/adr/madr/develop/template/adr-template.md) and a [minimal version](https://raw.githubusercontent.com/adr/madr/develop/template/adr-template-bare-minimal.md), too. ```markdown --- status: date: decision-makers: consulted: informed: --- # <!-- short title, representative of solved problem and found solution --> ## Context and Problem Statement ## Decision Drivers * <!-- decision driver --> ## Considered Options * <!-- option --> ## Decision Outcome Chosen option: "", because ### Consequences * Good, because * Bad, because ### Confirmation ## Pros and Cons of the Options ### <!-- title of option --> * Good, because * Neutral, because * Bad, because ## More Information ``` ### There's also [[ISO 42010]] Appendix A - "_Architecture decisions and rationale_" From the template: > [!cite] > When recording decisions, the following information items should be considered: > • unique identifier for the decision > • statement of the decision > • correspondences or linkages concerns to which it pertains • owner of the decision > • correspondences or linkages to affected AD elements > • rationale linked to the decision > • forces and constraints on the decision > • assumptions influencing the decision > • considered alternatives and their potential consequences ## Example - using the first proposed template ```plaintext # Use Radix-36 Strings for timestamps Date: 2024-08-21 ## Context Elements in the PDW need to be timestamped with absolute references to *when* they were created & updated, to enable data merging and general maintenance. Also PDW is meant to be uncoupled from and not bound to any **one** data tool. Different data tools approach timestamps differenty from one-another, and often are in conflict. Notably, Microsoft Excel causes problems with both storing timestamps as human-readable text dates and storing them as large numbers. A solution is needed to ensure a consistent canonical data model can be maintained without interpretation errors. The timestamp needs to be alphabetically sortable and relatively short. Also there is a desire for a lightweight solution that does not necessitate including large chunks of code for handling timestamping. ## Status Accepted ## Decision The canonical data model will use a custom `EpochStr` approach, where timestamps are recorded as "milliseconds since the epoch", then translated to a number in base-36. ## Consequences Timestamps in the canoncial data structure are not human-readable, but are sufficiently small, alphabetically sortable, and not likely to change via type inferencing by any particular tool (e.g. Excel). ``` # Misc - There's a [GitHub ADR Organization](https://github.com/adr) that is trying to promote the use of ADRs and provide templates & tooling - The term `Decision Log` may refer to the collection of ADRs. **** ## Source - Originally found & cited article: https://docs.structurizr.com/ui/decisions/ - https://cognitect.com/blog/2011/11/15/documenting-architecture-decisions - Subsequent reading: https://adr.github.io - Google's Page on them: https://cloud.google.com/architecture/architecture-decision-records ## Related - My current rewrite of the [[PDW]] is incorporating ADRs