= Schema

:Notice: Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE file distributed with this work for additional information regarding copyright ownership. The ASF licenses this file to you under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at. http://www.apache.org/licenses/LICENSE-2.0 . Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR  CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.


Most applications need to integrate with other apps in the enterprise.
To facilitate such integration scenarios, Apache Isis defines a number of standard XSD schemas:


* the xref:refguide:schema:mml.adoc[metamodel] schema, which allows the internal metamodel to be exported in a canonical fashion

* the xref:refguide:schema:cmd.adoc[command] schema, which captures the __intention__ of a user to invoke an action or edit a property

* the xref:refguide:schema:ixn.adoc[interaction execution] schema, which captures the actual execution of an action invocation/property edit

* the xref:refguide:schema:chg.adoc[changes] schema, which captures which objects have been created, updated or deleted as the result of an execution of an action invocation/property edit

These each use XSD types defined by the xref:refguide:schema:common.adoc[common schema] (most notably the `oidDto` complex type which identifies a domain object).

The xref:userguide:commandlog:about.adoc[Command Log] extension, xref:userguide:executionlog:about.adoc[Execution Log] and xref:userguide:executionoutbox:about.adoc[Execution Outbox] extensions all persist these objects, eg for auditing or integration purposes.

The sections below discuss these schemas in more detail.


