Open Metadata Repository Services (OMRS) Metadata Meta-Model

Figure 1: Overview of OMRS's metamodel

Figure 1: Overview of OMRS’s metadata metamodel

OMRS’s metamodel defines the structures used to represent metadata, and can be broadly divided into the following two areas:

Type Definitions (TypeDefs and AttributeTypeDefs)
Instances

Type Definitions (TypeDefs and AttributeTypeDefs)

TypeDefs define the general characteristics that are used to describe any general type – whether native or not – and typically fit into one of the following three general types (TypeDefCategory):

EntityDef: the definition of a type of entity
RelationshipDef: the definition of a type of relationship
ClassificationDef: the definition of a type of classification

TypeDefs are implemented as Java classes in Egeria (those in italics are abstract).

Figure 2: Type Definitions

Figure 2: Type Definitions

Examples

For example, the native OpenMetadataTypes that Egeria defines include:

a generic Referenceable entity type,
a GlossaryCategory entity type,
a GlossaryTerm entity type,
(and many others!)

Rather than being another set of classes that inherit from the general TypeDef classes (EntityDef, RelationshipDef, ClassificationDef), these open types are instantiated objects of one of those TypeDef classes (in the above examples, of the EntityDef class).

A set of TypeDefAttributes within the TypeDef defines the list of additional characteristics (properties) that each of these entity types can possess – things like names, descriptions, etc – which may naturally vary from one entity type to another. (These property-level definitions are AttributeTypeDefs.)

An example of a RelationshipDef is the linkage between GlossaryTerm and GlossaryCategory known as a TermCategorization, which is further defined to allow any number of linkages between the two, in either direction. Again, the TermCategorization will be an instantiated object of the class RelationshipDef, with various properties configured on it to define the endpoints of the relationship.

An example ClassificationDef is Confidentiality: that can apply to any Referenceable entity (hence including both GlossaryTerm and GlossaryCategory, as both of these extend the Referenceable entity type).

Figure 3: Example Type Definitions (from OpenMetadataTypes)

Figure 3: Example Type Definitions (from OpenMetadataTypes)

For example, the Referenceable is defined as follows as part of the OpenMetadataTypes:

final String guid            = "a32316b8-dc8c-48c5-b12b-71c1b2a080bf";
final String name            = "Referenceable";
final String description     = "An open metadata entity that has a unique identifier.";
final String descriptionGUID = null;

// The EntityDef object itself
EntityDef entityDef = archiveHelper.getDefaultEntityDef(guid,
                                                        name,
                                                        null,
                                                        description,
                                                        descriptionGUID);

List<TypeDefAttribute> properties = new ArrayList<>();
TypeDefAttribute       property;

final String attribute1Name            = "qualifiedName";
final String attribute1Description     = "Unique identifier for the entity.";
final String attribute1DescriptionGUID = null;
final String attribute2Name            = "additionalProperties";
final String attribute2Description     = "Additional properties for the element.";
final String attribute2DescriptionGUID = null;

// The TypeDefAttributes that define the properties of the Referenceable (EntityDef) object
property = archiveHelper.getStringTypeDefAttribute(attribute1Name,
                                                   attribute1Description,
                                                   attribute1DescriptionGUID);
property.setUnique(true);
properties.add(property);
property = archiveHelper.getMapStringStringTypeDefAttribute(attribute2Name,
                                                            attribute2Description,
                                                            attribute2DescriptionGUID);
properties.add(property);

entityDef.setPropertiesDefinition(properties);

And this results in a JSON structure like the following:

{
  "class": "EntityDef",
  "guid": "a32316b8-dc8c-48c5-b12b-71c1b2a080bf",
  "name": "Referenceable",
  "version": 1,
  "versionName": "1.0",
  "category": "ENTITY_DEF",
  "description": "An open metadata entity that has a unique identifier.",
  "origin": "bce3b0a0-662a-4f87-b8dc-844078a11a6e",
  "createdBy": "ODPi Egeria (OMRS)",
  "createTime": 1516313040008,
  "validInstanceStatusList": [
    "ACTIVE",
    "DELETED"
  ],
  "initialStatus": "ACTIVE",
  "propertiesDefinition": [
    {
      "attributeName": "qualifiedName",
      "attributeType": {
        "class": "PrimitiveDef",
        "version": 1,
        "versionName": "1.0",
        "category": "PRIMITIVE",
        "guid": "b34a64b9-554a-42b1-8f8a-7d5c2339f9c4",
        "name": "string",
        "primitiveDefCategory": "OM_PRIMITIVE_TYPE_STRING"
      },
      "attributeDescription": "Unique identifier for the entity.",
      "valuesMinCount": 0,
      "valuesMaxCount": 1,
      "indexable": true,
      "attributeCardinality": "AT_MOST_ONE",
      "unique": true
    },
    {
      "attributeName": "additionalProperties",
      "attributeType": {
        "class": "CollectionDef",
        "version": 1,
        "versionName": "1.0",
        "category": "COLLECTION",
        "guid": "005c7c14-ac84-4136-beed-959401b041f8",
        "name": "map<string,string>",
        "description": "A map from String to String.",
        "collectionDefCategory": "OM_COLLECTION_MAP",
        "argumentCount": 2,
        "argumentTypes": [
          "OM_PRIMITIVE_TYPE_STRING",
          "OM_PRIMITIVE_TYPE_STRING"
        ]
      },
      "attributeDescription": "Additional properties for the element.",
      "valuesMinCount": 0,
      "valuesMaxCount": 1,
      "indexable": true,
      "attributeCardinality": "AT_MOST_ONE",
      "unique": false
    }
  ]
}

Figure 4: Example JSON structure for a type definition (Referenceable)

Instances

Instances define individual instantiations of the TypeDefs: for example, individual GlossaryTerm entities (like “Address Line 1”) or GlossaryCategory entities (like “Coco Pharmaceuticals”), Confidentiality classifications (like “Sensitive”), etc.

Implemented instances will generally be objects of one of the following classes:

EntitySummary / EntityProxy / EntityDetail : information about one specific instance of an entity, at varying levels of detail
Relationship: information about a relationship between entities; the endpoints of the relationship are specified as EntityProxy objects
Classification: information that provides additional contextual information about a given entity, and is included in both the EntitySummary and EntityDetail views of an entity

Each of these will typically be further described by an InstanceProperties object that instantiates one or more properties used to describe the entity, classification or relationship.

Instances as a concept are implemented as generic Java classes in Egeria (those in italics are abstract).

Figure 5: Instances

Figure 5: Instances

Examples

Like TypeDefs, instances are managed as instantiated objects of the classes above (not as new classes that inherit from those above).

For example, to represent an “Address Line 1” GlossaryTerm, there can be:

an instantiated EntitySummary object providing a headline set of information about “Address Line 1” (ie. its classifications),
an instantiated EntityDetail object providing the full details of “Address Line 1” (all of its classifications and properties),
an instantiated EntityProxy object defining the unique properties of “Address Line 1” (ie. a qualifiedName property inherited from Referenceable which must be unique across all instances of the object)

The InstanceProperties associated with the EntityDetail, Relationship and Classification objects give the further detail on the object (ie. its name, summary, etc).

To represent a “Sensitive Confidentiality” concept that can be used to classify other information (like “Address Line 1”), we could have a “Confidentiality” Classification defined with a specific level (“Sensitive”) through its InstanceProperties
To represent the linkage between “Address Line 1” and a specific category location (like “Coco Pharmaceuticals/Terms”) we could have a Relationship representing the TermCategorization with one end pointing to an EntityProxy for “Address Line 1” and one end pointing to an EntityProxy for “Coco Pharmaceuticals/Terms”

Figure 6: Example instances (using open metadata types)

Figure 6: Example instances (using open metadata types)

As code, this example could be implemented using something like the following:

// ENTITIES

// Summary-level entity information (see end of CLASSIFICATION section for adding Classifications)
EntitySummary summary = new EntitySummary();
summary.setGUID(guid);
summary.setCreatedBy("...user...");
summary.setCreateTime(new Date(...));
summary.setUpdatedBy("...user...");
summary.setUpdateTime(new Date(...));

// Detailed-level entity information (see end of CLASSIFICATION section for adding Classifications)
EntityDetail detail = igcomrsRepositoryConnector.getRepositoryHelper().getSkeletonEntity(
        sourceName,
        omrsRepositoryConnector.getMetadataCollectionId(),
        InstanceProvenanceType.LOCAL_COHORT,
        userId,
        "GlossaryTerm"
);

detail.setStatus(InstanceStatus.ACTIVE);
detail.setGUID(guid);
detail.setCreatedBy("...user...");
detail.setCreateTime(new Date(...));
detail.setUpdatedBy("...user...");
detail.setUpdateTime(new Date(...));

InstanceProperties instanceProperties = new InstanceProperties();
PrimitivePropertyValue propertyValue = new PrimitivePropertyValue();
PrimitiveDef primitiveDef = new PrimitiveDef();
primitiveDef.setPrimitiveDefCategory(PrimitiveDefCategory.OM_PRIMITIVE_TYPE_STRING);
propertyValue.setPrimitiveValue("Address Line 1");
propertyValue.setPrimitiveDefCategory(primitiveDef.getPrimitiveDefCategory());
propertyValue.setTypeGUID(primitiveDef.getGUID());
propertyValue.setTypeName(primitiveDef.getName());

instanceProperties.setProperty("qualifiedName", propertyValue);

propertyValue.setPrimitiveValue("Street and street number");
instanceProperties.setProperty("summary", propertyValue);

detail.setProperties(instanceProperties);

// CLASSIFICATION

InstanceProperties properties = new InstanceProperties();

// The "Sensitive" level for the classification
EnumPropertyValue level = new EnumPropertyValue();
level.setSymbolicName("Sensitive");
properties.setProperty("level", level);

// Creating a new classification, of "Confidentiality", applying to "Referenceable", with
// the "Sensitive" level defined above
Classification classification = omrsRepositoryConnector.getRepositoryHelper().getNewClassification(
        sourceName,
        userId,
        "Confidentiality",
        "Referenceable",
        ClassificationOrigin.ASSIGNED,
        null,
        properties
);

ArrayList<Classificaton> classifications = new ArrayList<>();
classifications.add(classification);

// ... adding the Classification(s) to the Entity(Summary|Detail)
summary.setClassifications(classifications);
detail.setClassifications(classifications);

// RELATIONSHIP

// Define the qualifiedName property with the unique name for the first end of the relationship
// (the GlossaryCategory end of the relationship)
InstanceProperties uniqueProperties1 = new InstanceProperties();
PrimitivePropertyValue propertyValue = new PrimitivePropertyValue();
PrimitiveDef primitiveDef = new PrimitiveDef();
primitiveDef.setPrimitiveDefCategory(PrimitiveDefCategory.OM_PRIMITIVE_TYPE_STRING);
propertyValue.setPrimitiveValue("Coco Pharmaceuticals/Terms");
propertyValue.setPrimitiveDefCategory(primitiveDef.getPrimitiveDefCategory());
propertyValue.setTypeGUID(primitiveDef.getGUID());
propertyValue.setTypeName(primitiveDef.getName());
uniqueProperties1.setProperty("qualifiedName", propertyValue);

EntityProxy entityProxy1 = omrsRepositoryConnector.getRepositoryHelper().getNewEntityProxy(
        sourceName,
        omrsRepositoryConnector.getMetadataCollectionId(),
        InstanceProvenanceType.LOCAL_COHORT,
        userId,
        "GlossaryCategory",
        uniqueProperties1,
        null
);

// Define the qualifiedName property with the unique name of the second end of the relationship
// (the GlossaryTerm end of the relationship)
InstanceProperties uniqueProperties2 = new InstanceProperties();
primitiveDef.setPrimitiveDefCategory(PrimitiveDefCategory.OM_PRIMITIVE_TYPE_STRING);
propertyValue.setPrimitiveValue("Address Line 1");
propertyValue.setPrimitiveDefCategory(primitiveDef.getPrimitiveDefCategory());
propertyValue.setTypeGUID(primitiveDef.getGUID());
propertyValue.setTypeName(primitiveDef.getName());
uniqueProperties2.setProperty("qualifiedName", propertyValue);

EntityProxy entityProxy2 = omrsRepositoryConnector.getRepositoryHelper().getNewEntityProxy(
        sourceName,
        omrsRepositoryConnector.getMetadataCollectionId(),
        InstanceProvenanceType.LOCAL_COHORT,
        userId,
        "GlossaryTerm",
        uniqueProperties2,
        null
);

// Define the relationship between the two EntityProxy objects instantiated above
Relationship omrsRelationship = new Relationship();
InstanceProperties relationshipProperties = new InstanceProperties();
PrimitivePropertyValue relationProperty = new PrimitivePropertyValue();

relationProperty.setTypeGUID("...");
relationProperty.setTypeName("???");
relationshipProperties.setProperty("TermCategorization", relationProperty);
omrsRelationship.setProperties(relationshipProperties);
omrsRelationship.setEntityOneProxy(entityProxy1);
omrsRelationship.setEntityTwoProxy(entityProxy2);
omrsRelationship.setGUID("...");

More information on types

For more information on the OpenMetadataTypes that are covered by and included with Egeria, see the open metadata type system.

License: CC BY 4.0, Copyright Contributors to the ODPi Egeria project.