Meta Model

meta-model is a model that describes models.

The name

If the name was analogous to other models it would be called model-model, just like a model for animals would be called animal-model.

General

The main entity type is GmMetaModel which denotes a model.

Note this name is slightly misleading, the correct name would be GmModel, but because of the type's importance it would be hard to change it.

A model instance reflects the types the model declares and what other models it depends on.

In this article, we will explore its structure and inspect its elements.

For general information about models, see Models.

Basic Structure

Below you can find an overview of the meta-model's basic structure, depicting its most relevant elements.

Important Elements

Type	Abstract	Purpose	Properties
`GmMetaModel` extends: `GmModelElement`	false	Depicts models and the meta-model itself	name: `string` version: `string` types: `set<GmType>`
`GmModelElement` extends: `StandardIdentifiable`	true	Super type for meta-model elements
`GmType` extends: `GmModelElement`	true	Super type for all types	typeSignature: `string` declaringModel: `GmMetaModel`
`GmEntityType` extends: `GmCustomType`	false	Custom GM-types	superTypes: `set<GmEntityType>` properties: `set<GmProperty>` evaluatesTo: `GmType` isAbstract: `boolean`
`GmProperty` extends: `GmPropertyInfo`	false	Custom GM-model element to depict details of an entity type	name: `string` isAbstract: `boolean` type: `GmType` declaringType: `GmEntityType`
`GmMapType` extends: `GmCollectionType`	false	GM-collection type allowing to hold elements depicted by key-type and value-type	keyType: `GmType` valueType: `GmType`
`GmLinearCollectionType` extends: `GmCollectionType`	true	Super type for linear collection types	elementType: `GmType`
`GmListType` extends: `GmLinearCollectionType`	false	Linear GM-collection type allowing to hold a number of ordered elements depicted by elementType
`GmSetType` extends: `GmLinearCollectionType`	false	Linear GM-collection type allowing to hold a number of un-ordered elements depicted by elementType
`GmBaseType` extends: `GmType`	false	`GmType` of properties with the type `object`
`GmSimpleType` extends: `GmScalarType`	true	Super type for simple scalar types
`GmBooleanType` extends: `GmSimpleType`	false	`GmType` of properties with the type `boolean`
`GmDateType` extends: `GmSimpleType`	false	`GmType` of properties with the type `date`
`GmDecimalType` extends: `GmSimpleType`	false	`GmType` of properties with the type `decimal`
`GmFloatType` extends: `GmSimpleType`	false	`GmType` of properties with the type `float`
`GmIntegerType` extends: `GmSimpleType`	false	`GmType` of properties with the type `integer`
`GmLongType` extends: `GmSimpleType`	false	`GmType` of properties with the type `long`
`GmStringType` extends: `GmSimpleType`	false	`GmType` of properties with the type `string`
`GmDoubleType` extends: `GmSimpleType`	false	`GmType` of properties with the type `double`

GmProperty

Allows to instantiate properties, which depict the details of an entity type.

Important Elements

Type	Abstract	Purpose	Properties
`GmProperty` extends: `GmPropertyInfo`	false	Custom GM-model element to depict details of an entity type	name: `string` nullable: `boolean` type: `GmType` declaringType: `GmEntityType` typeRestriction: `GmTypeRestriction`
`GmTypeRestriction` extends: `GmModelElement`	false	Allows to restrict which type a property can have	types: `list<GmType>` Definition of allowed types keyTypes: `list<GmType>` Used for restriction on map-keys allowVd: `boolean` Allow the use of value descriptors, e.g. `now()` for date-values keyAllowVd: `boolean` Similar to `allowVd`, but for map-keys
`QualifiedProperty` extends: `StandardIdentifiable`	false	Used to reference a property along with a given entity	property: `GmProperty` entityType: `GmEntityType`
`PropertyPath` extends: `StandardIdentifiable`	false	Standard representation of property path, e.g. `Company.ceo.companyCar.brand`	properties: `list<GmProperty>`

Info Types

Info-Types allow to enrich model elements to make them more specific to their nature.

Important Elements

Type	Abstract	Purpose	Properties
`GmCustomModelElement` extends: `GmModelElement`	true	Super-type for all info-types
`GmCustomTypeInfo` extends: `GmCustomModelElement` `HasMetadata`	true	Provides the properties `metadata` and `declaringModel` to its sub-types.	declaringModel: `GmMetaModel`
`GmEntityTypeInfo` extends: `GmCustomTypeInfo`	true	Enriching of entity types.	See Overrides and Metadata
`GmEnumTypeInfo` extends: `GmCustomTypeInfo`	true	Enriching of enum types.	See Overrides and Metadata
`GmEnumConstantInfo` extends: `GmCustomModelElement`, `HasMetadata`	true	Enriching of enum constants.	See Overrides and Metadata
`GmPropertyInfo` extends: `GmCustomModelElement`, `HasMetadata`	true	Enriching of properties.	initializer: `object` See Overrides and Metadata

Overrides

Overrides allow to apply metadata without changing the original entity. Without an override a metadata configuration on a type from model dependency will apply on that model globally. With an override this can be avoided - the configuration will only apply to your local model.

In addition, metadata allows you to change the declaringTypeInfo, i.e. although a property might be inherited, its origin can be mimicked such, that the sub-type seems to be the declaring type. Further, overrides allow to specify initial values on inherited properties without changing them at the origin.

See the Metadata section for a use-case.

Important Elements

Type	Abstract	Purpose	Properties
`GmCustomTypeOverride` extends: `GmCustomTypeInfo`	false	Abstract super-type for GmEntityOverride and GmEnumTypeOverride. Referenced from `GmMetaModel` via `typeOverrides`
`GmEntityTypeOverride` extends: `GmCustomTypeInfo`	false	Specific override for entity types	propertyOverrides: `list<GmPropertyOverride>` entityType: `GmEntityType`
`GmEnumTypeOverride` extends: `GmCustomTypeInfo`	false	Specific override for enum types	constantOverrides: `list<GmEnumConstantOverride>` enumType: `GmEnumType`
`GmEnumConstantOverride` extends: `GmEnumConstantInfo`	false	Overrides enum constants	declaringTypeOverride: `GmEnumOverride` enumConstant: `GmEnumConstant`
`GmPropertyOverride` extends: `GmCustomModelElement`	false	Overrides properties	declaringTypeInfo: `GmEntityTypeInfo` property: `GmProperty`

Metadata

Metadata are used to configure models specifically to use cases. To enable this, the meta-model has a dependency to the basic meta-data-model.

For more information, see Metadata.

Important Elements

Type	Abstract	Purpose	Properties	Overrides
`HasMetadata` extends: `GenericEntity`	true	Abstract type from meta-data-model. Has property `metadata` to be inherited by custom types, properties and enum constants	metadata: `Metadata`
`Metadata` extends: `StandardIdentifiable`	true	Abstract type from meta-data-model. Provides the actual metadata configuration.	conflictPriority: `double` important: `boolean` inherited: `boolean` selector: `MetaDataSelector`
`GmEntityTypeInfo` extends: `GmCustomTypeInfo`	true	Enriching of entity types. Makes use of overriding.	propertyMetadata: `set<Metadata>`	propertyOverride:`TypeRestriction` types:`PropertyMetaData` `UniversalMetaData`
`GmEnumTypeInfo` extends: `GmCustomTypeInfo`	true	Enriching of entity types. Makes use of overriding.	enumConstantMetadata: `set<Metadata>`	propertyOverride:`TypeRestriction` types: `EnumConstantMetaData` `UniversalMetaData` propertyOverride: `metadata` declaringTypeInfo: `GmEntityTypeInfo`
`GmPropertyInfo` extends: `GmCustomModelElement`, `HasMetadata`	true	Enriching of properties. Makes use of overriding.	initializer: `object`	propertyOverride:`metadata` declaringTypeInfo: `GmPropertyInfo`
`GmEnumConstantInfo` extends: `GmCustomModelElement`, `HasMetadata`	true	Enriching of enum constants. Makes use of overriding.	initializer: `object`	propertyOverride:`metadata` declaringTypeInfo: `GmEnumConstantInfo`

Meta Model

On this page

The name

General

Basic Structure

Important Elements

GmProperty

Important Elements

Info Types

Important Elements

Overrides

Important Elements

Metadata

Important Elements