<h1 id="rules-engine">Rules Engine<a aria-hidden="true" class="anchor-heading icon-link" href="#rules-engine"></a></h1>
<p>A rules engine can be visualized as a set of if-then-else statements to implement some business logic of our application.</p>
<p>Example: determining car insurance premiums</p>
<pre><code>if car.owner.hasCellPhone then premium += 100;
if car.model.theftRating > 4 then premium += 200;
if car.owner.livesInDodgyArea &#x26;&#x26; car.model.theftRating > 2 then premium += 300;
</code></pre>
<p>A rules engine is a tool that makes it easier to program using this computational model</p>
<p>An important property of rule engines is chaining - where the action part of one rule changes the state of the system in such a way that it alters the value of the condition part of other rules.</p>
<ul>
<li>Chaining sounds appealing, since it supports more complex behaviors, but can easily end up being very hard to reason about and debug.
<ul>
<li>Often, it is easy to set up a rules system, but very hard to maintain it because nobody can understand this implicit program flow; a consequence of leaving the imperative computational model</li>
</ul>
</li>
</ul>
<h1 id="e-resources">E Resources<a aria-hidden="true" class="anchor-heading icon-link" href="#e-resources"></a></h1>
<ul>
<li><a href="https://martinfowler.com/bliki/RulesEngine.html">Martin Fowler thoughts on why to avoid a rules engine</a></li>
<li><a href="https://github.com/cachecontrol/json-rules-engine">JSON rules engine repo</a></li>
</ul>
<hr>
<strong>Backlinks</strong>
<ul>
<li><a href="/notes/7n3tUhrwbvz8nNu0bTlWz">EventBridge</a></li>
</ul>

Rules Engine

tech

This Dendron vault of tech knowledge is organized according to domains and their sub-domains, along with specific implementation of those domains.

For instance, Git itself is a domain. Sub-domains of Git would include topics like `commit`,
`tags`, `reflog` etc., while implementations of each of those could be `cli`, `strat`
(strategies), `inner` (inner workings), and so on.

The goal of the wiki is to present data in a manner that is from the perspective
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from a specific domain. For instance, if a user wants to use postgres functions
and hasn't done them in a while, they should be able to query
`postgres.functions` to see basic implementations, as well as common patterns
that have been employed in the past.

This wiki has been written with myself in mind. While learning each of these
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insights as they arose. I have refrained from capturing information that I
considered obvious or otherwise non-beneficial to my own understanding.

As a result, I have allowed myself to use potentially arcane concepts to help
explain others. For example, in my note on [[unit testing|testing.method.unit]],
I have made reference to the [[microservices|general.arch.microservice]] note.
The ability to analogize between different concepts captured in different notes
allows an opportunity to build strong generalized understandings. Given that
you'd have to understand microservices to be able to draw that same parallel
that I've already drawn, these links won't work for everyone. Since these notes
are written for myself, I have been fine with taking these liberties and leaning
on them heavily.

What I hope to gain from this wiki is the ability to step away from any
given domain for a long period of time, and be able to be passably useful for
whatever my goals are within a short period of time. Of course this is all
vague sounding, and really depends on the domain along with the ends I am
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To achieve this, the system should be steadfast to:
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This Dendron notebook is the sister vault to the general [Second Brain](https://tech.kyletycholiz.com).

## Tags
Throughout the garden, I have made use of tags, which give semantic meaning to the pieces of information.

- `ex.` - Denotes an *example* of the preceding piece of information
- `spec:` - Specifies that the preceding information has some degree of *speculation* to it, and may not be 100% factual. Ideally this gets clarified over time as my understanding develops. I try to go back after I have better understood the topic and clear out the notes of `spec:` tags
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- `mn:` - Denotes a *mnemonic*
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## Resources
### UE (Unexamined) Resources
Often, I come across sources of information that I believe to be high-quality. They may be recommendations or found in some other way. No matter their origin, I may be in a position where I don't have the time to fully examine them (and properly extract notes), or I may not require the information at that moment in time. In cases like these, I will add reference to a section of the note called **UE Resources**. The idea is that in the future when I am ready to examine them, I have a list of resources that I can start with. This is an alternative strategy to compiling browser bookmarks, which I've found can quickly become untenable.

### E (Examined) Resources
Once a resource has been thoroughly examined and has been mined for notes, it will be moved from *UE Resources* to *E Resources*. This is to indicate that (in my own estimation), there is nothing more to be gained from the resource that is not already in the note.

### Resources
This heading is for inexhaustible resources. 
- A prime example would be a quality website that continually posts articles.  - Another example would be a tool, such as software that measures frequencies in a room to help acoustically treat it.
