Origin emf/engineering.yml 1:1
Uri engineering://nasdanika/modules/core/modules/emf

Nasdanika EMF module contains classes for working with Ecore models. These classes can be categorized as follows:

  • General purpose - helper classes such as EMFUtil.
  • Adapters and adapter factories - base classes for building (reflective) adapters and composite adapter factories in order to adapt Ecore models to required functionality.
  • Model execution - base classes for “wiring” Ecore models into the Nasdanika Execution Model, i.e. making the models executable including command line execution.
  • Persistence - classes for loading Ecore models from key-value data sources with special support of YAML.


Adapters mechanism allows to adapt a model element to another type. Adapters are used by, say HTML Flow to adapt Core Flow to org.nasdanika.html.model.app.util.ActionProviders in order to generate an action model and then generate a web site from the action model.

Adapters allow to separate concerns and to have multiple adapters and adapter factories for the same model. For example, an action model can be transformed to a static web site or Eclipse help using different adapters.

Adapters are created by adapter factories which are registered with a resource set.

Below is a code snippet demonstrating the process of transforming a flow model to an action model by adapting the root model element to ActionProvider and then creating an Action instance:

// Create a resource set and load a model
ResourceSet instanceModelsResourceSet = createResourceSet();
Resource instanceModelResource = instanceModelsResourceSet.getResource(URI.createURI("mymodel.xml"), true);

// Add an adapter factory
instanceModelsResourceSet.getAdapterFactories().add(new EngineeringActionProviderAdapterFactory(context)); {

// Resource set for a target (action) model		
ResourceSet actionModelsResourceSet = createResourceSet();
actionModelsResourceSet.getResourceFactoryRegistry().getExtensionToFactoryMap().put(org.eclipse.emf.ecore.resource.Resource.Factory.Registry.DEFAULT_EXTENSION, new XMIResourceFactoryImpl());
org.eclipse.emf.ecore.resource.Resource actionModelResource = actionModelsResourceSet.createResource(URI.createURI("myactions.xml"));

// Getting the root object of the source model		
EObject instance = instanceModelResource.getContents().get(0);

// Adapting the root to ActionProvider and calling execute() to obtain an action
Action rootAction = EObjectAdaptable.adaptTo(instance, ActionProvider.class).execute(...);

// Adding the root action to a resource and then saving to a file

Adapter factories

Below is a summary of Nasdanika EMF adapters:

See JavaDoc for more details.

Model execution

Nasdanika EMF provides the following CLI command classes:


Nasdanika EMF persistence allows to load Ecore models from key-value sources such as:

  • java.util.Function<String,Object>.apply(String key)
  • JSON
  • YAML

Loading from YAML and JSON can be used to implement <problem doman>-as-code:

  • DEefine models in YAML or JSON,
  • Edit in a text editor or in a web browser using version control system Web UI,
  • Store in a version control system,
  • Keep track of model element definition source - file (URI), line, number, origin and commit (see Marker below),
  • Diff and merge as code.

The persistence framework uses EAnnotation with urn:org.nasdanika source to customize loading. This annotation is referred further as “Nasdanika annotation”

The persistence framework loads EObject structural features which are:

  • Changeable
  • Not changeable with computed key of Nasdanika annotation set to true - in this case the feature value is loaded from the source, but not injected into the object - it is available via load tracking for custom handling - see below.
  • Load key (see below) is not null.

Load keys


EObject features are loaded using load keys. By default load keys are derived from feature names by converting camel case to kebab case. E.g. firstName becomes first-name.

Load key can be customized using the Nasdanika annotation:

  • load-key detail key at the feature level. The value shall be a string.
  • load-keys detail key at the class level. The value shall be a YAML map of feature names to load keys. This approach allows to override feature load key in subclasses.
  • loadable detail key at the feature level - set it to false to suppress loading of features even if they are changeable. Please note that it is different from computed - computed forces loading of values of non-changeable features, and loadable suppresses loading of changeable features.
  • feature-key detail key at the feature level. The value shall be a string. Feature key is used as a fallback value for a load key and also for computing containment path.
  • feature-keys detail key at the class level. The value shall be a YAML map. This annotation can be defined on a subclass of the class defining the feature, which allows to override the default (kebab case) feature key.

The above process of resolving load keys is used by the default load key provider. Load keys can be customized by passing a non-default load key provider to org.nasdanika.emf.persistence.EObjectLoader constructor.

Classes and packages

Default load keys for classes and packages are computed in the same way as for features by converting class or package name from came to kebab case.

Default behavior can be customized using the load-key Nasdanika annotation detail key with the load key as value. It is also possible to suppress loading of a class or a package by setting loadable Nasdanika annotation detail key to false.

As with features, it is possible to provide a custom key loader to EObjectLoader constructor to change the default behavior if annotations are not enough. A custom key loader may fall-back/chain/delegate to the default key loader.

In the below example of loading of Exec Text

   description: Full text definition
   interpolate: false
   content: Hello ${token}.
  • content - Package name converted to kebab case.
  • text - Class name converted to kebab case.
  • description, interpolate, content - object features.

Default feature

A feature can be defined as a default feature by setting default-feature Nasdanika annotation to true at the feature level or to the feature name at the class level. Default features are used when object configuration value is not a map, e.g. a String.

For example, Exec Text defines content as its default feature. It allows to load text from the following YAML specifications:

Full definition
   description: Full text definition
   interpolate: false
   content: Hello ${token}.
Short definition

Just content (default feature):

Single line
content-text: World
content-text: |+2
  Line 1.
  Line 2.

Loading references

By default configuration values of reference elements shall be single-entry maps with the type as a key and a value as configuration. The loading process instantiates an EObject by its key and then injects features from the value.

For example,

    - engineering-product:
        path: core
        name: Core
        owners: engineering://nasdanika/engineers/joe-doe
        experts: engineering://nasdanika/engineers/joe-doe
        action-prototype: "ncore.genmodel.xml#/"
            name: "0.1"
            increment: engineering://nasdanika/increments/2021/children/Q4            
            name: "1.0"
  • modules - is an interited reference of Organization (see All > References)
  • engineering-product is the element type - engineering package, product type.
  • path, name, … are object features

In many cases reference values are either of the same type or their type can be derived from their configuration keys. In this case explicitly specifying the type is unnecessary and may lead to configuration errors. For example, in the above code snippet releases reference can contain only instances of its reference type - Release.

To specify that the type of refernce elements shall be derived from the reference type or annotations instead of being supplied explicitly set homogenous Nasdanika annotation details key to true on the reference.

In some situations the type of reference element can be derived from the type of its configuration - string, integer, map, list, boolean, date. In such cases add reference-type Nasdanika annotation key with a value containing a YAML map of configuration value types to element types.

For example:

map: MapProperty
list: ListProperty
string: StringProperty
integer: IntegerProperty

Map values can be strings for types in the same EPackage or maps with the following keys:

  • ns-uri - Namespace URI of the EPackage.
  • name - EClass name.

In situations when it is necessary to override reference type in a subclass add reference-types Nasdanika annotation to the subclass. The value shall be a YAML map of reference names to element types. Element types can be strings for the types in the same package or maps with ns-uri and name keys as explained above.

By default, if an element value of a homogenous reference is a string then it is treated as a relative URI of a resource from which the element shall be loaded. In this case that resource has to contain type definition. For elements with a default feature this behavior can be modified by setting strict-containment Nasdanika annotation detail to true to treat the string value in configuration as the value of the default feature. In this case it is not possible to load reference elements from external resources.

Reference keys (EKeys)

References may specify attributes of their types as EKeys. References which specify EKeys can be loaded from maps. Currently only a single EKey is supported. Support of multiple EKeys will be added when needed.

When a reference with EKeys is loaded from a map, map entry key is injected into the element object’s EKey attributes. The map entry value is used to either set up element features or “value feature”.

Value feature

When using EKeys you may want to use map entry value to set a specific feature of the reference element instead of using it to configure the element itself. In this case set value-feature Nasdanika annotation on the reference to the name of the feature which shall be configured with the map entry value.

File sets

It is possible to load zero or more objects into a reference using fileset: URI schema followed by the file set specification.

The specification can be a string, a YAML array, or a YAML map.

In some cases if a patterns starts with * it is treated as a YAML alias which would lead to a ScannerException being thrown. To solve it add ./ in front of * e.g. ./*/engineering.yml.


If it is a string, then it is treated as an Ant path pattern.

Example: fileset:issues/*.yml


If it is an array, then elements are treated as Ant path patterns.

Example: fileset:[issues/*.yml]


If it is a map, the following keys are supported:

  • include - a string or an array of strings with Ant path patterns to include into the result.
  • exclude - a string or an array of strings with Ant path patterns to exclude from the matched include result.
  • base - Base directory resolved relative to the context URI.


Single line: fileset:{include:*.yml;exclude:done_*.yml;base:issues}


    - |+2
          - *.yml
          - *.yaml
        exclude: done_*.*
        base: issues

Mutually exclusive features

Features may have exclusive-with Nasdanika annotation details containing a space-separated list of feature keys which are exclusive with the annotated feature. It is not necessary to declare exclusivity on both features, just on one of them.

If object configuration contains keys for mutually exclusive features, loading will fail.

Load tracker

During load a org.nasdanika.common.persistence.LoadTracker adapter is added to objects being loaded. This adapter allows, for example, to compute derived values for features unless they were already loaded. It also allows to access values of computed features - these values are stored in the adapter, but not injected into the target object because these features are not changeable.

An example of using a computed feature - the feature type is an object which is loaded from an external system, e.g. an issue tracker. Feature configuration value is a string, e.g. an issue ID. During load issue ID is stored in the load tracker adapter and then is used to contact the issue tracker system, retrieve issue details and create an issue object to be returned from the feature getter.


When objects are loaded from YAML information about source file line and number is injected into the objects as follows:

  • An adapter of type org.nasdanika.common.persistence.Marked is added to the object.
  • If the object extends Marked, then Marker is added to the object.

It is possible to customize marker type by calling EObjectLoader.setMarkerFactory(). For example, GitMarker can be created with org.nasdanika.emf.persistence.GitMarkerFactory.


For examples see Exec tests.

MS Excel resources

Loading models from MS Excel resources can be done with org.nasdanika.emf.persistence.ExcelResourceFactory class. This class takes care of reading and updating the workbook on save. Loading of model elements from sheets and rows shall be implemented by subclasses.

You can find an example/test case in TestExcel.