First, read OAL introduction.
Here is the official scrips is the generated-analysis-x.y.z.jar/official_analysis.oal file in distribution, also the official_analysis.oal in source code repository.
Notice, this file doesn't effect anything in runtime, although included in distribution. You need to use OAL tool code generator to build the real analysis codes from it. All generated codes are under oal folder in oap-server/generated-analysis/target/generated-sources.
All metrics named in this script could be used in alarm and UI query. Of course, you can change this scripts and re-generate the analysis process and metrics, such as adding filter condition.
If you try to add or remove some metrics, UI may break, we only recommend you to do this when you plan to build your own UI based on the customization analysis core.