Merge branch 'readme-update' into 'master'

Updating release cadence verbage on main README.md

See merge request big-bang/bigbang!2701

README.md

@@ -24,15 +24,15 @@ Additional information can be found at [Big Bang Docs](https://docs-bigbang.dso.
 
 ## Getting Started
 
-- You will need to instantiate a Big Bang environment tailored to your needs.  [The Big Bang customer template](https://repo1.dso.mil/platform-one/big-bang/customers/template/) is provided for you to copy into your own Git repository and begin modifications.
+- You will need to instantiate a Big Bang environment tailored to your needs. [The Big Bang customer template](https://repo1.dso.mil/big-bang/customers/template/) is provided for you to copy into your own Git repository and begin modifications.
 
 ## Contributing to Big Bang
 
 There are 3 main ways to contribute to Big Bang:
 
-- [Contribute to the Big Bang Team's Backlog](https://repo1.dso.mil/platform-one/big-bang/bigbang/-/issues)
-- [Contribute to open-source projects under the Big Bang Technical Oversight Committee (BBTOC)](https://repo1.dso.mil/platform-one/bbtoc/-/blob/master/CONTRIBUTING.md)
-- [Submit new package proposals](https://repo1.dso.mil/platform-one/bbtoc/-/issues/new?issue%5Bmilestone_id%5D=)
+- [Contribute to the Big Bang Team's Backlog](https://repo1.dso.mil/big-bang/bigbang/-/issues)
+- [Contribute to open-source projects under the Big Bang Technical Oversight Committee (BBTOC)](https://repo1.dso.mil/big-bang/product/bbtoc/-/blob/master/CONTRIBUTING.md)
+- [Submit new package proposals](https://repo1.dso.mil/big-bang/product/bbtoc/-/issues/new?issue%5Bmilestone_id%5D=)
   - Please review the [package integration guide](./docs/developer/package-integration/README.md) if you are interested in submitting a new package
   - A shepherd will be assigned to the project to create a repo in the [BB sandbox](https://repo1.dso.mil/platform-one/big-bang/apps/sandbox)
 
@@ -40,8 +40,43 @@ Additional information can be found in the [contributing guide](./CONTRIBUTING.m
 
 ## Release Schedule
 
-- Big Bang releases every 2 weeks with a minor release number. In order to stay current with all features and security updates ensure you are no more than `n-2` releases behind.
-  - To see what is on the roadmap please see our [project milestones](https://repo1.dso.mil/groups/platform-one/big-bang/-/milestones)
+- Big Bang releases adopt a standardized versioning based on and loosely following the [Semantic Versioning 2.0.0 guidelines](https://semver.org/spec/v2.0.0.html) (major.minor.patch). These releases aren't based on a fixed schedule and instead the specifics in the scheme are as follows:
+
+  ### Patch Version
+
+  A patch version increment is performed when there is a change in the tag (version number) of a Big Bang core package or a
+  bug fix for a Big Bang template or values files.
+  A change in the patch version number should be backwards compatible
+  with previous patch changes within a minor version.  If there is a significant functionality change in the
+  a core package that requires adjustments to Big Bang templates, this would require a change in the minor or major version
+  depending on the impact to the values and secrets used to integrated the package with Big Bang.
+  
+  NOTE: Patch versions would not typically be created for addon package updates, rather customers would be expected to be 
+  updating those packages via `git.tag`/`helmRepo.tag` changes directly, or "inheriting" those updates through another version.
+  
+  ### Minor Version
+  
+  A minor version increment is required when there is a change in the integration of Big Bang with core or addon packages.
+  As examples the following changes warrant a Minor version change:
+  
+  - Change in the umbrella values.yaml (except for changes to package version keys)
+  - Change in any Big Bang templates (non bug fix changes)
+  
+  Minor version changes should be backwards compatible.
+  
+  ### Major Version
+  
+  A major version increment indicates a release that has significant changes, which could potentially break
+  compatibility with previous versions. A major change is required when there are changes to the architecture of Big Bang or
+  critical values file keys.  For example removing a core package or changing significant values that propagate to all core
+  and add-on packages are considered major version changes. As examples of major version changes:
+  
+  - Removal or renaming of Big Bang values.yaml top level keys (e.g., istio, git repository values, etc.)
+  - Change to the structure of chart/templates files or key values.
+  - Additional integration between core/add-on packages that require change to the charts of all packages.
+  - Modification of Big Bang GitOps engine (i.e. switching from FluxCD -> ArgoCD)
+
+- To see what is on the roadmap or included in a given release you can still review our [project milestones](https://repo1.dso.mil/groups/big-bang/-/milestones)
 
 ## Community