Java Tooling for Working with Aspect Models

General Considerations

In this section, the Java APIs for working with Aspect Models are described. All of the components described in the following subsections can either be included in your project using a dedicated dependency (as described in the respective subsection), or you can use the aspect-model-starter artifact that aggregates all necessary dependencies:

Maven

<dependency>
    <groupId>io.openmanufacturing</groupId>
    <artifactId>sds-aspect-model-starter</artifactId>
    <version>2.1.0</version>
</dependency>

Gradle Groovy DSL

implementation 'io.openmanufacturing:sds-aspect-model-starter:2.1.0'

Gradle Kotlin DSL

implementation("io.openmanufacturing:sds-aspect-model-starter:2.1.0")

The error handling in many APIs is done using the Try type provided by the Java library Vavr. This is similar to a java.lang.Optional in that a successful result can be processed using .map() or .flatMap(), but if an error occurs, the object can also provide the original exception. Compared with throwing exceptions, using a Try<T> as a return type instead has the advantage of enabling composable and better readable code. Please see the Vavr User Guide for more information.

Getting the right version

The tooling can be made available in two different versions: release and milestone. The release version represents a stable version of the product and can be referenced in your projects in the usual way from the Maven Central repository. There is also the possibility to have the intermediate builds made available, these are called milestone builds. Instead of Maven Central, these are released via GitHub Packages mechanism.
To be able to use the artifacts released in this way in your projects, first the right repository has to be added to your pom.xml file:

<repositories>
  <repository>
	 <id>github</id>
	 <name>OpenManufacturingPlatform SDS-SDK</name>
	 <url>https://maven.pkg.github.com/OpenManufacturingPlatform/sds-sdk</url>
	 <releases><enabled>true</enabled></releases>
	 <snapshots><enabled>true</enabled></snapshots>
  </repository>
</repositories>

Then the desired dependencies can be referenced in the usual way. For an example, please refer to Github - Installing a package.

JDK requirements

The sds-sdk components are built with Java 17 and require a JDK >= 17 such as Adoptium Temurin.

The sds-sdk can also be used with a Java 17-compatible GraalVM JDK. With GraalVM you need to make the Graal JavaScript component available, as parts of the SDK such as the Aspect Model validation component require embedded JavaScript execution:

For using the sds-sdk in the GraalVM itself, install the JS component using the GraalVM Updater: gu install js
For using the sds-sdk with GraalVM native-image, be sure to use the --language:js option when building the native image; for more information see polyglot programming.

Parsing Aspect Model URNs

The aspect-model-urn artifact provides a way to parse and validate Aspect model element URNs as described in the specification.

import io.openmanufacturing.sds.aspectmodel.urn.AspectModelUrn;

final AspectModelUrn urn = AspectModelUrn.fromUrn( "urn:bamm:com.example:1.0.0#Example" );

System.out.println( urn.getNamespace() ); // com.example
System.out.println( urn.getName() );      // Example
System.out.println( urn.getVersion() );   // 1.0.0
System.out.println( urn.getUrnPrefix() ); // urn:bamm:com.example:1.0.0#

To include the artifact, use the following dependencies:

Maven

<dependency>
    <groupId>io.openmanufacturing</groupId>
    <artifactId>sds-aspect-model-urn</artifactId>
    <version>2.1.0</version>
</dependency>

Gradle Groovy DSL

implementation 'io.openmanufacturing:sds-aspect-model-urn:2.1.0'

Gradle Kotlin DSL

implementation("io.openmanufacturing:sds-aspect-model-urn:2.1.0")

Loading and Saving Aspect Models

Aspect models are, like their Meta Model, described using the Resource Description Format (RDF, [rdf11]) and the Terse RDF Triple Language syntax (TTL, [turtle]). There are two ways of working with Aspect models: Either the model is loaded as an RDF model where the abstraction level directly corresponds to the RDF/Turtle serialization, or the RDF is parsed into a native Java Aspect model representation where the abstraction level corresponds to the BAMM concepts. Both approaches have different use cases and advantages and both are supported by the Aspect model Java tooling:

Working on the RDF level Using the Java Aspect model

Working on the RDF level	Using the Java Aspect model
Low level, focus on power and flexibility Flexibly navigate and filter the model on the RDF statements level Work with models that are valid RDF, but incomplete Aspect models, e.g. in Aspect model editors Use SPARQL [sparql] to execute complex queries on Aspect models	High level, focus on convenience and type-safety Use Aspect-model specific interfaces for type-safe code Use Java-native data types (e.g. `java.math.BigInteger` for `xsd:integer`) Easily traverse the model on the abstraction level of Aspect model elements

Low level, focus on power and flexibility
Flexibly navigate and filter the model on the RDF statements level
Work with models that are valid RDF, but incomplete Aspect models, e.g. in Aspect model editors
Use SPARQL [sparql] to execute complex queries on Aspect models

High level, focus on convenience and type-safety
Use Aspect-model specific interfaces for type-safe code
Use Java-native data types (e.g. java.math.BigInteger for xsd:integer)
Easily traverse the model on the abstraction level of Aspect model elements

As a rule of thumb, if your use case mostly consists of consuming Aspect models, you should prefer the Java Aspect model, if you create or edit Aspect models, this is better done using the RDF API.

Understanding Model Resolution

Loading an Aspect model in either the RDF-based or the Java Aspect model-based APIs does not only comprise parsing the Turtle file, but also the resolution of elements on the RDF level:

An Aspect model refers to meta model elements (everything that starts with bamm:), and can refer to namespaces of shared elements (bamm-c, bamm-e and unit)
It can also refer to elements from other Aspect models or model elements defined in separate Turtle files

You use the model resolver to load an Aspect model, which takes care of the first point: The used meta model elements and elements from shared namespaces are automatically resolved and added to the loaded RDF model. For the second point, you need to provide the model resolver with the information on where to find other Aspect models: In memory, in a local file system, in a remote model repository etc. This is done using a resolution strategy, which is a function from some type T to a Try of a RDF model. Several commonly used resolution strategies are readily available:

The FileSystemStrategy resolves a java.nio.file.Path for a file relative to the models directory
The UrnFileSystemStrategy resolves a AspectModelUrn to a file in the models directory
The InMemoryStrategy resolves a model against an already loaded Apache Jena RDF model
The SequenceStrategy can be used to chain two different strategies of the same type
The EitherStrategy can be used to chain two different strategies of different types

To implement custom resolution strategies (e.g., to resolve models against a different blob storage API), you can base your implementation on the AbstractResolutionStrategy. Using the model resolver requires at least one resolution strategy that can resolve AspectModelUrns (because references in an Aspect model to external model elements use their respective URNs) and can use another resolution strategy, for example for file paths. The following sections show examples for the different variants.

Loading an Aspect Model to work on the RDF Level

Consider the following example:

import java.nio.file.Path;
import java.nio.file.Paths;

import org.apache.jena.rdf.model.Model;
import org.apache.jena.rdf.model.Property;
import org.apache.jena.rdf.model.RDFList;
import org.apache.jena.rdf.model.RDFNode;
import org.apache.jena.rdf.model.Resource;
import org.apache.jena.rdf.model.ResourceFactory;
import org.apache.jena.vocabulary.RDF;

import io.openmanufacturing.sds.aspectmodel.resolver.AspectModelResolver;
import io.openmanufacturing.sds.aspectmodel.resolver.FileSystemStrategy;
import io.openmanufacturing.sds.aspectmodel.resolver.ResolutionStrategy;
import io.openmanufacturing.sds.aspectmetamodel.KnownVersion;
import io.openmanufacturing.sds.aspectmodel.urn.AspectModelUrn;

import io.vavr.control.Either;

final Path modelsRoot = Paths.get( "/path/to/models-root" );
final ResolutionStrategy fileSystemStrategy = new FileSystemStrategy( modelsRoot ); (1)

new AspectModelResolver()
      .resolveAspectModel( fileSystemStrategy,
            AspectModelUrn.fromUrn( "urn:bamm:io.openmanufacturing.test:1.0.0#Example" ) )
      .forEach( versionedModel -> {
         final KnownVersion metaModelVersion = versionedModel.getVersion();
         final Model model = versionedModel.getModel();

         // Do something with the RDF model:
         // List the names of the Properties of the Aspect in the model
         final String bammPrefix = String.format( "urn:bamm:io.openmanufacturing:meta-model:%s#",
               metaModelVersion.toVersionString() );
         final Resource aspectClassResource = ResourceFactory.createResource( bammPrefix + "Aspect" );
         final Property propertiesResource = ResourceFactory.createProperty( bammPrefix + "properties" );
         final Resource aspectResource = model (2)
               .listStatements( null, RDF.type, aspectClassResource )
               .nextStatement()
               .getSubject();
         model.listStatements( aspectResource, propertiesResource, (RDFNode) null ) (3)
              .nextStatement()
              .getObject()
              .as( RDFList.class )
              .asJavaList()
              .stream()
              .map( RDFNode::asResource )
              .map( Resource::getLocalName )
              .forEach( System.out::println );
      } );

1	The example uses the `FileSystemStrategy` to refer to an Aspect model file in a local file system, following the models directory structure.
2	The RDF resource for the Aspect is retrieved from the RDF model, and
3	used to print the Aspect’s Properties.

To include the model resolver artifact, use the following dependencies:

Maven

<dependency>
    <groupId>io.openmanufacturing</groupId>
    <artifactId>sds-aspect-model-resolver</artifactId>
    <version>2.1.0</version>
</dependency>

Gradle Groovy DSL

implementation 'io.openmanufacturing:sds-aspect-model-resolver:2.1.0'

Gradle Kotlin DSL

implementation("io.openmanufacturing:sds-aspect-model-resolver:2.1.0")

Loading an Aspect Model to work on the Java Aspect Model Level

Consider the following example:

import java.nio.file.Path;
import java.nio.file.Paths;

import io.openmanufacturing.sds.aspectmodel.resolver.AspectModelResolver;
import io.openmanufacturing.sds.aspectmodel.resolver.FileSystemStrategy;
import io.openmanufacturing.sds.aspectmodel.resolver.ResolutionStrategy;
import io.openmanufacturing.sds.aspectmodel.urn.AspectModelUrn;
import io.openmanufacturing.sds.metamodel.IsDescribed;
import io.openmanufacturing.sds.metamodel.loader.AspectModelLoader;

final Path modelsRoot = Paths.get( "/path/to/models-root" );
final ResolutionStrategy fileSystemStrategy = new FileSystemStrategy( modelsRoot ); (1)

new AspectModelResolver()
      .resolveAspectModel( fileSystemStrategy,
            AspectModelUrn.fromUrn( "urn:bamm:io.openmanufacturing.test:1.0.0#Example" ) )
      .flatMap( AspectModelLoader::fromVersionedModel ) (2)
      .forEach( aspect -> (3)
            aspect.getProperties().stream()
                  .map( IsDescribed::getName )
                  .forEach( System.out::println ) );

1	The example uses the `FileSystemStrategy` to refer to an Aspect model file in a local file system, following the models directory structure.
2	The Aspect Loader turns the RDF model into the Java Aspect model representation.
3	The Java model is used to print the Aspect’s Properties.

To include the Java Aspect model artifact, use the following dependencies:

Maven

<dependency>
    <groupId>io.openmanufacturing</groupId>
    <artifactId>sds-aspect-meta-model-java</artifactId>
    <version>2.1.0</version>
</dependency>

Gradle Groovy DSL

implementation 'io.openmanufacturing:sds-aspect-meta-model-java:2.1.0'

Gradle Kotlin DSL

implementation("io.openmanufacturing:sds-aspect-meta-model-java:2.1.0")

Serializing a Java Aspect Model into a RDF/Turtle Aspect Model

There are two serialization components available: One to turn a Java Aspect model into a Jena RDF model (the reverse operation of what the AspectModelLoader does) and one to serialize the resulting Jena RDF model in Turtle syntax, formatted according to the guidelines described in the BAMM specification.

import java.io.PrintWriter;

import org.apache.jena.rdf.model.Model;

import io.openmanufacturing.sds.aspectmodel.resolver.services.VersionedModel;
import io.openmanufacturing.sds.aspectmodel.serializer.PrettyPrinter;
import io.openmanufacturing.sds.aspectmodel.serializer.RdfModelCreatorVisitor;
import io.openmanufacturing.sds.aspectmodel.urn.AspectModelUrn;
import io.openmanufacturing.sds.metamodel.Aspect;
import io.openmanufacturing.sds.metamodel.vocabulary.Namespace;

// Aspect as created by the AspectModelLoader
final Aspect aspect = ...

// First step: Turn Java Aspect model into a Jena RDF model
final Namespace aspectNamespace = () -> aspect.getAspectModelUrn().toString();
final RdfModelCreatorVisitor rdfCreator = new RdfModelCreatorVisitor(
      aspect.getMetaModelVersion(), aspectNamespace );
final Model model = rdfCreator.visit( aspect );

// At this point, you can manipulate the RDF model, if required

// Second step: Serialize RDF model into nicely formatted Turtle
final PrintWriter printWriter = new PrintWriter( System.out );
final PrettyPrinter prettyPrinter = new PrettyPrinter( new VersionedModel( model, aspect.getMetaModelVersion() ),
      aspectNamespace, printWriter );
prettyPrinter.print();

To include the serializer artifact, use the following dependencies:

Maven

<dependency>
    <groupId>io.openmanufacturing</groupId>
    <artifactId>sds-aspect-model-serializer</artifactId>
    <version>2.1.0</version>
</dependency>

Gradle Groovy DSL

implementation 'io.openmanufacturing:sds-aspect-model-serializer:2.1.0'

Gradle Kotlin DSL

implementation("io.openmanufacturing:sds-aspect-model-serializer:2.1.0")

Validating Aspect Models

Consider the following example:

import java.util.stream.Collectors;

import io.openmanufacturing.sds.aspectmodel.resolver.services.VersionedModel;
import io.openmanufacturing.sds.aspectmodel.validation.report.ValidationError;
import io.openmanufacturing.sds.aspectmodel.validation.report.ValidationReport;
import io.openmanufacturing.sds.aspectmodel.validation.services.AspectModelValidator;

import io.vavr.control.Try;

// Versioned model as returned by the AspectModelResolver
final Try<VersionedModel> versionedModel = ...;

final AspectModelValidator validator = new AspectModelValidator(); (1)
final ValidationReport validationReport = validator.validate( versionedModel );

if ( validationReport.conforms() ) { (2)
   System.out.println( "The model is valid" );
} else {
   // The Validation Report indicates that the validation has failed.

   // Variant 1: Call .toString() on the validationReport
   System.out.println( validationReport.toString() ); (3)

   // Variant 2: Custom processing of different types of validation errors
   final String customErrorMessage = validationReport.getValidationErrors().stream().<String> map(
         validationError -> validationError.accept( new ValidationError.Visitor<>() { (4)
            @Override
            public String visit( final ValidationError.Syntactic error ) {
               // Separately access line and column numbers of the syntax error
               return "...";
            }

            @Override
            public String visit( final ValidationError.Semantic error ) {
               // Separately access focus node, result path, validator message and value
               // of the error
               return "...";
            }

            @Override
            public String visit( final ValidationError.Processing error ) {
               // Access the processing error message and stack trace of the error
               return "...";
            }
         } ) ).collect( Collectors.joining( ", " ) );

   System.out.println( customErrorMessage );
}

1	An Aspect model validator is created and its validation is called on the Aspect model.
2	The `.conforms()` method can be used to checked if the model is valid or not.
3	To retrieve a preformatted error message in case the Aspect model is invalid, the validation report can be turned into a String.
4	If more flexibility is required, e.g. for creating error messages in different languages or formats such as JSON, the validation error can also accept an implementation of a `ValidationError.Visitor`, that distinguishes between the different types of validation failures: syntax errors, semantic errors (i.e., the input is valid RDF but violates the Aspect model contract) and processing errors (e.g., a file could not be accessed).

To include the model validator, use the following dependencies:

Maven

<dependency>
    <groupId>io.openmanufacturing</groupId>
    <artifactId>sds-aspect-model-validator</artifactId>
    <version>2.1.0</version>
</dependency>

Gradle Groovy DSL

implementation 'io.openmanufacturing:sds-aspect-model-validator:2.1.0'

Gradle Kotlin DSL

implementation("io.openmanufacturing:sds-aspect-model-validator:2.1.0")

Generating Documentation for Aspect Models

Different types of artifacts can be generated from an Aspect model. All corresponding generators are included in the following dependency:

Maven

<dependency>
    <groupId>io.openmanufacturing</groupId>
    <artifactId>sds-aspect-model-document-generators</artifactId>
    <version>2.1.0</version>
</dependency>

Gradle Groovy DSL

implementation 'io.openmanufacturing:sds-aspect-model-document-generators:2.1.0'

Gradle Kotlin DSL

implementation("io.openmanufacturing:sds-aspect-model-document-generators:2.1.0")

The documentation generation APIs provide methods that take as an argument a Function<String, java.io.OutputStream>. This is a mapping function that takes a file name as an input (which is determined by the respective generator) and returns a corresponding OutputStream, for example (but not necessarily) a FileOutputStream. By providing this function when calling the generator method, you can control where the output is written to, even when the generator creates multiple files. For the code examples in the following subsections, we assume that the following method is defined for calling the generators:

OutputStream outputStreamForName( final String aspectFileName ) {
   // Create an OutputStream for the file name, e.g. a FileOutputStream
   ...
}

Generating SVG or PNG Diagrams

Using the AspectModelDiagramGenerator, automatically layouted diagrams can be created for Aspect models in the formats PNG, SVG and Graphviz/DOT.

import java.io.FileOutputStream;
import java.io.OutputStream;
import java.util.Locale;
import java.util.Set;

import io.openmanufacturing.sds.aspectmodel.diagramgenerator.AspectModelDiagramGenerator;
import io.openmanufacturing.sds.aspectmodel.diagramgenerator.AspectModelDiagramGenerator.Format;
import io.openmanufacturing.sds.aspectmodel.resolver.services.VersionedModel;

// Versioned model as returned by the AspectModelResolver
final VersionedModel versionedModel = ...

final AspectModelDiagramGenerator generator = new AspectModelDiagramGenerator( versionedModel ); (1)

// Variant 1: Generate a diagram in SVG format using @en descriptions and preferredNames from the model
final OutputStream output = new FileOutputStream( "..." );
generator.generateDiagram( Format.SVG, Locale.ENGLISH, output ); (2)
output.close();

// Variant 2: Generate diagrams in multiple formats, for all languages that are present in the model.
generator.generateDiagrams( Set.of( Format.PNG, Format.SVG ), this::outputStreamForName ); (3)

1	The diagram generator is initialized with the loaded model.
2	The simple call for one output format and one language (i.e., descriptions and preferredNames of one locale) takes one output stream to write the image to.
3	It is also possible to generate multiple diagrams, one for each combination of output format and language. For that, the set of target formats is given as well as a mapping function.

Generating HTML Documentation

A HTML reference documentation for an Aspect model can be generated as shown in the following code sample. The documentation contains an overview diagram and describes the model elements as specified in the Aspect model. Preferred names and descriptions in the respective language from the Aspect model are shown in the resulting document as part of each model element.

import java.io.OutputStream;

import io.openmanufacturing.sds.aspectmodel.asciidoc.AspectModelDocumentationGenerator;
import io.openmanufacturing.sds.aspectmodel.resolver.services.VersionedModel;

// Versioned model as returned by the AspectModelResolver
final VersionedModel versionedModel = ...

final AspectModelDocumentationGenerator generator = new AspectModelDocumentationGenerator( versionedModel );
generator.generateHtml( this::outputStreamForName );

Generating Sample JSON Payload

The sample JSON payload generator is used to create a valid JSON payload for an Aspect model as it could be returned by an Aspect that implements that Aspect model. This follows the mapping rules as defined in the Meta Model specification. The generator uses bamm:exampleValues of Properties if present, otherwise random values corresponding to the respective data types are generated.

import io.openmanufacturing.sds.aspectmodel.generator.json.AspectModelJsonPayloadGenerator;

// Versioned model as returned by the AspectModelResolver
final VersionedModel versionedModel = ...

final AspectModelJsonPayloadGenerator generator = new AspectModelJsonPayloadGenerator( versionedModel );

// Variant 1: Direct generation into a String
final String jsonString = generator.generateJson();

// Variant 2: Generate using mapping function
generator.generateJson( this::outputStreamForName );

Generating JSON Schema

The JSON schema generator creates a JSON Schema that describes the payload for an Aspect model as it could be returned by an Aspect that implements that Aspect model. Currently, the generated schema corresponds to

import java.io.ByteArrayOutputStream;
import io.openmanufacturing.sds.aspectmodel.generator.jsonschema.AspectModelJsonSchemaGenerator;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;

// Aspect as created by the AspectModelLoader
final Aspect aspect = ...

// Generate the JSON Schema
final AspectModelJsonSchemaGenerator generator = new AspectModelJsonSchemaGenerator();
final JsonNode jsonSchema = generator.apply( aspect, Locale.ENGLISH );

// If needed, print or pretty print it into a string
final ByteArrayOutputStream out = new ByteArrayOutputStream();
final ObjectMapper objectMapper = new ObjectMapper();

objectMapper.writerWithDefaultPrettyPrinter().writeValue( out, jsonSchema );
final String result = out.toString();

Generating OpenAPI Specification

The OpenAPI specification generator creates either a JSON Schema or a Yaml Spec that specifies an Aspect regarding to the OpenApi specification. The currently used versions corresponds Draft 4 of the JSON Schema specification, and 3.0.1.

import java.util.Optional;
import java.io.ByteArrayOutputStream;
import io.openmanufacturing.sds.aspectmodel.generator.openapi.AspectModelOpenApiGenerator;
import io.openmanufacturing.sds.aspectmodel.generator.openapi.PagingOption;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;

// Aspect as created by the AspectModelLoader
final Aspect aspect = ...

//Server url i.e. http://www.example.com
final String baseUrl = ...

// The resource path which shall be added i.e. /testPath/{parameter}
final String resourcePath = ...

// A String containing all the information for in the resource path mentioned dynamic properties. The string must be syntactially valid YAML.
// A definition for a dynamic property is mandatory as you won't be able to define which sort of data have to be used.
// I.e for the above used path:
//parameter:
//  name: parameter
//  in: path
//  description: A parameter.
//  required: true
//  schema:
//    type: string
final Optional<String> yamlProperties = ...

//If the query api shall be added to the generated specification.
final boolean includeQueryApi = ...

// The paging Option to be chosen. In case paging is possible: default for a time related collection is time-based paging.
// Otherwise the default is offset-based paging.
final Optional<PagingOption> pagingOption = ...

// Generate pretty-printed YAML
final AspectModelOpenApiGenerator generator = new AspectModelOpenApiGenerator();
final String yaml = generator.applyForYaml( aspect, useSemanticVersion, baseUrl, resourcePath, yamlProperties, includeQueryApi, pagingOption );


//A JsonNode containing all the information for in the resource path mentioned variable properties.
final final Optional<JsonNode> jsonProperties = ...

// Generate the JSON
final AspectModelOpenApiGenerator generator = new AspectModelOpenApiGenerator();
final JsonNode json = generator.apply( aspect, useSemanticVersion, baseUrl, resourcePath, jsonProperties, includeQueryApi, pagingOption );

// If needed, print or pretty print it into a string
final ByteArrayOutputStream out = new ByteArrayOutputStream();
final ObjectMapper objectMapper = new ObjectMapper();

objectMapper.writerWithDefaultPrettyPrinter().writeValue( out, json );
final String result = out.toString();

For Enumerations with complex data types, the values are modelled as instances of the Entity defined as the Enumeration’s data type (see Declaring Enumerations for more information). In case the Entity instances contain Properties with a sorted collection as their data type, the order of the values of said collection in the Entity instances is not preserved in the generated OpenAPI specification. Preserving this order in OpenAPI is not possible at this point.

Generating Java Code for Aspect Models

Java code can be generated from an Aspect model in two ways:

The generated code represents the Aspect payload. Aspects and Entities become Java classes; their Properties become fields in the classes. Characteristics are not first-class elements, but are implicitly represented by the usage of corresponding data types (e.g. using java.util.Set as the type for the Set Characteristic of a Property) or javax.validation annotations. The generated classes can be used in a straightforward fashion, but they do not contain information about the underlying Aspect model such as its version number. Parts of the Aspect model that have no representation in its corresponding JSON payload are not part of those classes either, in particular descriptions and preferred names. These classes are called POJOs (Plain Old Java Objects), as they do not contain logic but serve mainly as data containers.
The generated code represents the Aspect model itself: It is a type-safe variant of the model and includes every information that is also present in the model such as Characteristics, descriptions including language tags and original XSD data types. It is however not intended to store payload corresponding to an Aspect. Theses classes are called static meta classes, because they are created at compile time (static) and talk about the structure of the information, not the information itself (meta).

Depending on the use case, you would either use one or both of the types simultaneously.

To include the Java generator, use the following dependencies:

Maven

<dependency>
    <groupId>io.openmanufacturing</groupId>
    <artifactId>sds-aspect-model-java-generator</artifactId>
    <version>2.1.0</version>
</dependency>

Gradle Groovy DSL

implementation 'io.openmanufacturing:sds-aspect-model-java-generator:2.1.0'

Gradle Kotlin DSL

implementation("io.openmanufacturing:sds-aspect-model-java-generator:2.1.0")

Type Mapping

In the Java code generated from an Aspect model, the scalar Aspect model data types are mapped to native Java types. The following table lists the correspondences.

Aspect model type Java native type

Aspect model type	Java native type
`xsd:string`	`java.lang.String`
`xsd:boolean`	`java.lang.Boolean`
`xsd:decimal`	`java.math.BigDecimal`
`xsd:integer`	`java.math.BigDecimal`
`xsd:double`	`java.lang.Double`
`xsd:float`	`java.lang.Float`
`xsd:date`	`javax.xml.datatype.XMLGregorianCalendar`
`xsd:time`	`javax.xml.datatype.XMLGregorianCalendar`
`xsd:dateTime`	`javax.xml.datatype.XMLGregorianCalendar`
`xsd:dateTimeStamp`	`javax.xml.datatype.XMLGregorianCalendar`
`xsd:gYear`	`javax.xml.datatype.XMLGregorianCalendar`
`xsd:gMonth`	`javax.xml.datatype.XMLGregorianCalendar`
`xsd:gDay`	`javax.xml.datatype.XMLGregorianCalendar`
`xsd:gYearMonth`	`javax.xml.datatype.XMLGregorianCalendar`
`xsd:gMonthDay`	`javax.xml.datatype.XMLGregorianCalendar`
`xsd:duration`	`javax.xml.datatype.Duration`
`xsd:yearMonthDuration`	`javax.xml.datatype.Duration`
`xsd:dayTimeDuration`	`javax.xml.datatype.Duration`
`xsd:byte`	`java.lang.Byte`
`xsd:short`	`java.lang.Short`
`xsd:int`	`java.lang.Integer`
`xsd:long`	`java.lang.Long`
`xsd:unsignedByte`	`java.lang.Short`
`xsd:unsignedShort`	`java.lang.Integer`
`xsd:unsignedInt`	`java.lang.Long`
`xsd:unsignedLong`	`java.math.BigInteger`
`xsd:positiveInteger`	`java.math.BigInteger`
`xsd:nonNegativeInteger`	`java.math.BigInteger`
`xsd:negativeInteger`	`java.math.BigInteger`
`xsd:nonPositiveInteger`	`java.math.BigInteger`
`xsd:hexBinary`	`byte[]`
`xsd:base64Binary`	`byte[]`
`xsd:anyURI`	`java.net.URI`
`bamm:curie`	`io.openmanufacturing.metamodel.datatypes.Curie`

xsd:string

java.lang.String

xsd:boolean

java.lang.Boolean

xsd:decimal

java.math.BigDecimal

xsd:integer

java.math.BigDecimal

xsd:double

java.lang.Double

xsd:float

java.lang.Float

xsd:date