Create unique naming spec (apache#31)

* crate unique naming spec

spec/Naming.md

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+# Naming
+
+We define the unique name strategy per datasource to ensure it is followed uniformly independently from the type of job consuming and producing data.
+The namespace for a dataset is the unique name for its datasource.
+For jobs it is the scheduler.
+
+## Datasets:
+The namespace and name of a datasource can be combined to form a URI (scheme:[//authority]path)
+* Namespace = scheme:[//authority] (the datasource)
+* Name = path (the datasets)
+
+### Data warehouses/data bases.
+Datasets are called tables. Tables are organised in databases and schemas.
+#### Postgres:
+Datasource hierarchy:
+ * Host
+ * Port
+
+Naming hierarchy:
+ * Database
+ * Schema
+ * Table
+
+Identifier:
+ * Namespace: postgres://{host}:{port} of the service instance.
+   * Scheme = postgres
+   * Authority = {host}:{port}
+ * Unique name: {database}.{schema}.{table}
+   * URI =  postgres://{host}:{port}/{database}.{schema}.{table}
+
+#### Snowflake
+See: [Object Identifiers — Snowflake Documentation](https://docs.snowflake.com/en/sql-reference/identifiers.html)
+
+Datasource hierarchy:
+ * account name
+
+Naming hierarchy:
+ * Database: {database name} => unique across the account
+ * Schema: {schema name} => unique within the database
+ * Table: {table name} => unique within the schema
+
+Identifier:
+ * Namespace: snowflake://{account name}
+   * Scheme = snowflake
+   * Authority = {account name}
+ * Name: {database}.{schema}.{table}
+   * URI =   snowflake://{account name}/{database}.{schema}.{table}
+
+#### BigQuery
+See: 
+[Creating and managing projects | Resource Manager Documentation](https://cloud.google.com/resource-manager/docs/creating-managing-projects)
+[Introduction to datasets | BigQuery](https://cloud.google.com/bigquery/docs/datasets-intro)
+[Introduction to tables | BigQuery](https://cloud.google.com/bigquery/docs/tables-intro)
+
+Datasource hierarchy:
+ * bigquery
+
+Naming hierarchy:
+ * Project Name: {project name} => is not unique
+ * Project number: {project number} => numeric: is unique across google cloud
+ * Project ID: {project id} => readable: is unique across google cloud
+ * dataset: {dataset name} => is unique within a project
+ * table: {table name} => is unique within a dataset
+
+Identifier :
+ * Namespace: bigquery
+   * Scheme = bigquery
+   * Authority = 
+ * Unique name: {project id}.{dataset name}.{table name}
+   * URI =   bigquery:{project id}.{schema}.{table}
+
+### Distributed file systems/blob stores
+#### GCS
+Datasource hierarchy: none, naming is global
+
+Naming hierarchy:
+ * bucket name => globally unique
+ * Path 
+
+Identifier :
+ * Namespace: gs://{bucket name}
+   * Scheme = gs
+   * Authority = {bucket name}
+ * Unique name: {path}
+   * URI =   gs://{bucket name}{path}
+
+#### S3
+Naming hierarchy:
+ * bucket name => globally unique
+ * Path 
+
+Identifier :
+ * Namespace: s3://{bucket name}
+   * Scheme = s3
+   * Authority = {bucket name}
+ * Unique name: {path}
+   * URI =   s3://{bucket name}{path}
+
+#### HDFS
+Naming hierarchy:
+ * Namenode: host + port
+ * Path
+
+Identifier :
+ * Namespace: hdfs://{namenode host}:{namenode port}
+   * Scheme = hdfs
+   * Authority = {namenode host}:{namenode port}
+ * Unique name: {path}
+   * URI =   hdfs://{namenode host}:{namenode port}{path}
+
+## Schedulers
+### Airflow
+
+Naming hierarchy:
+ * job => workspace/DAG
+ * Task => unique within the job
+
+Identifier :
+ * Namespace: {scheduler namespace}
+ * Unique name: {job}.{task}