Domain model#

This page introduces core concepts in the Katalyst domain model and how they relate to each other.

Bases#

The most central concept in Katalyst is a base: a storage system that holds content (data) and supports a specific set of operations. Katalyst is compatible with several different types of backend: filesystems, key-value stores, relational databases, etc.

An operation is something a base lets you do with data: read, list, aggregate, write, and eventually query. Which operations a base supports, and what structural commitments those operations require, is the subject of progressive operations.

In addition to natively-supported operations for various backends, Katalyst provides two very useful kinds of operation.

A check makes an assertion about content and reports a violation if the condition fails. See Checks.
An inspector is the descriptive dual of a check: it gathers and reports the state of content. See Inspectors.

Domain model diagram showing project containing base, collection, item, and attribute, with checks and inspectors operating on the data model.

Raw vs collection-configured bases#

When configuring a base, the most important division is between raw content and collectionized content. A base configured only for raw content supports only a limited set of operations: checks, inspections and a small set of fixes. Most operations that require writes are not permitted, because the system would not have the context necessary to guarantee that the new content is correct.

When a base is configured with collections, it can guarantee correctness and consistency for more operations. Check and inspect operations can be more specific and context-aware. Far more write operations are available, since the system now has more context to enable correctness and consistency.

Within a given base, collection configs do not replace raw configs. Instead, they stack on top. Similarly, operations that require a collection stack on top of those available when the base was only configured for raw access to content.

Projects#

A project is the whole workspace Katalyst operates over: a configured root that includes one or more bases, plus some additional metadata.