> ## Documentation Index
> Fetch the complete documentation index at: https://honeydew.ai/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Apache Ossie (OSI)

[Apache Ossie](https://ossie.apache.org/) (OSI), formerly the Open Semantic Interchange,
is a vendor-neutral, open-source specification for portable semantic
model definitions. It gives BI tools, AI agents, and warehouses a
shared YAML/JSON format for datasets, relationships, fields, and metrics,
so the same definitions can travel across tools without manual
reconciliation. It is now an incubating project at the Apache Software Foundation.

Honeydew is one of the founding partners of Apache Ossie (OSI), alongside
Snowflake, Salesforce, and dbt. Portable semantics are
core to how Honeydew approaches a semantic layer: the same metric or
attribute definition should mean the same thing in every tool that
consumes it. See the
[announcement post](https://honeydew.ai/blog/osi-is-cool-why-honeydew-joined-open-semantic-interchange/)
for context on why Honeydew joined.

<Note>
  Apache Ossie is an early specification under active development (current draft
  `0.2.0.dev0`). Concepts, field names, and mappings may change before the
  specification stabilizes.
</Note>

## Concept Mapping

Apache Ossie (OSI) and Honeydew model the same problem space, but the
granularity differs. The table below maps each Apache Ossie concept to its
Honeydew equivalent.

| Apache Ossie Concept                 | Honeydew Equivalent                                                              |
| ------------------------------------ | -------------------------------------------------------------------------------- |
| `semantic_model`                     | A Honeydew [workspace](/docs/architecture)                                            |
| `dataset`                            | An [Entity](/docs/modeling/entities) with its [Source Data](/docs/modeling/source-data)    |
| `dataset.source`                     | Entity [Source Data](/docs/modeling/source-data)                                      |
| `dataset.primary_key`, `unique_keys` | Entity granularity and [unique keys](/docs/modeling/entities)                         |
| `relationship`                       | A [Relation](/docs/modeling/relations) between entities                               |
| `field` (column reference)           | A [Source Attribute](/docs/modeling/source-data#columns)                              |
| `field` (computed expression)        | A [Calculated Attribute](/docs/calculations/attributes)                               |
| `field.dimension.is_time`            | A time attribute, often backed by a [time spine](/docs/advanced-modeling/time-spines) |
| `metric`                             | A [Metric](/docs/calculations/metrics)                                                |
| `expression.dialects`                | Compiled to the target warehouse dialect (Snowflake, Databricks, BigQuery)       |
| `ai_context`                         | [AI Metadata](/docs/integration/context-layer/ai-metadata) on the object              |
| `custom_extensions`                  | Honeydew-specific properties in the [YAML schema](/docs/yaml-schema)                  |

### Concepts Honeydew Adds Beyond Apache Ossie (OSI)

Apache Ossie defines the portable metadata layer. Honeydew implements that layer
and adds the operational machinery a semantic layer needs in production:

* **Query compiler and BI integration** — metrics and attributes compile
  to warehouse SQL exposed through
  [SQL](/docs/integration/sql-interface), [XMLA](/docs/integration/xmla-interface),
  [GraphQL](/docs/integration/graphql-api), and [MCP](/docs/integration/mcp)
  interfaces, with native integrations on top of those interfaces into
  [Power BI](/docs/integration/bi-tools/powerbi),
  [Tableau](/docs/integration/bi-tools/tableau),
  [Excel](/docs/integration/bi-tools/excel), and
  [other BI tools](/docs/integration/bi-tools/supported-tools).
* **AI Context Layer** — Apache Ossie carries `ai_context` metadata on
  individual objects; Honeydew adds a full
  [context layer](/docs/integration/context-layer/context-management) above
  the semantic layer (instructions, analytical skills, external
  business knowledge, and historical memory) and an agentic AI
  analysis engine that combines context retrieval with semantic
  compilation — [deep analysis](/docs/integration/context-layer/deep-analysis),
  [agents](/docs/integration/context-layer/agents),
  [Slack](/docs/integration/context-layer/slack-app), and
  [Teams](/docs/integration/context-layer/teams-app) apps.
* **Domains** — [hierarchical projections](/docs/domains) of the same
  semantic model for different audiences (finance vs. marketing,
  regional sales, an AI agent's scope). A domain selects entities and
  fields, applies mandatory filters, and overrides parameters; domains
  extend and compose other domains, so one model serves many
  perspectives without duplication.
* **Aggregate awareness** — semantic-aware query rewriting to
  [pre-aggregated tables](/docs/performance/aggregate-awareness), alongside
  [incremental aggregate updates](/docs/performance/aggregate-incremental-updates)
  and [entity caching](/docs/performance/entity-caching) for further
  performance.
* **Security and access control** —
  [row-level security](/docs/security/row-level-security) and
  [access control](/docs/access-control/user-access-control), enforced from
  the query interface down to the warehouse.
* **Workflow, environments, and deployment** — the semantic model is
  YAML and inherently git-native; Honeydew adds the workflow around it:
  [workspaces](/docs/governance/workspaces),
  [environments](/docs/governance/environments), and promotion paths for
  dev/staging/prod.

## Converting To and From Apache Ossie (OSI)

Honeydew provides a bidirectional converter between Apache Ossie and the
Honeydew workspace format, maintained in the Apache Ossie repository under
[`converters/honeydew`](https://github.com/apache/ossie/tree/main/converters/honeydew):

* **Apache Ossie → Honeydew** — import an Apache Ossie semantic model and
  produce a Honeydew workspace (entities, relations, attributes, metrics, AI
  metadata). See [Import Tools](/docs/migration/import-tools#apache-ossie-osi).
* **Honeydew → Apache Ossie** — export a Honeydew workspace as an Apache Ossie
  semantic model for consumption by other tools that support it.

Because Apache Ossie is still evolving, the converter tracks the current draft
of the specification and may change as the specification stabilizes.

## Stay Updated

The Apache Ossie (OSI) specification is evolving. Track progress on the
[Apache Ossie GitHub repository](https://github.com/apache/ossie)
and [working groups](https://github.com/apache/ossie/blob/main/docs/working_groups.md).