Difference between revisions of "Facet Based Resource Model"

Latest revision as of 18:15, 26 January 2023

The Information System Model (henceforth IS Model) is used by Information System Resource Registry

Disclaimer

This Model is part of research conducted in the context of a PhD. This wiki page represents just a partial view of the full rationale of the research. To have a complete overview of the rationale of the model, please refer to the PhD thesis which is publicly available at:

https://etd.adm.unipi.it/t/etd-05102019-114151/

https://openportal.isti.cnr.it/doc?id=people______::470484e51fcb9e307a418c800efc44c8

If you need to refer to such work you can cite the PhD Thesis.

BibText:

@phdthesis{frosini2019transactional,
  title={Transactional REST Information System for Federated Research Infrastructures enabling Virtual Research Environments},
  author={Frosini, Luca},
  year={2019},
  school={UNIVERSIT{\`A} DI PISA}
}

An previous paper about this work is:

BibText:

@article{frosini2018facet,
  title={A Facet-based Open and Extensible Resource Model for Research Data Infrastructures.},
  author={Frosini, Luca and Pagano, Pasquale},
  journal={Grey Journal (TGJ)},
  volume={14},
  number={2},
  year={2018}
}

IS Model

The Information System Model (henceforth IS Model) is a graph model with Entities as nodes and Relations as edges.

• Two typologies of entities are envisaged:
  • Resources, i.e. entities representing a description of "thing" to be managed;
    • Every Resource is described by a number of Facets.
  • Facets, i.e. entities contributing to "build" a description of a Resource. Every facet, once attached to a Resource profile captures a certain aspect / characterization of the resource;
    • Every facet is characterised by a number of properties;

• Two typologies of relations are envisaged:
  • isRelatedTo, i.e. a relation linking any two Resources.
  • ConsistsOf, i.e. a relation connecting each Resource with one of the Facets characterizing it;

• Each entity and relation
  • has an header automatically generated for the sake of identification and provenance of the specific information;
  • can be specialized
    • A number of specializations are identified below. Such specializations are managed by the gCube Core services, i.e. Core services builds upon these specializations to realize its management tasks;
    • Other specializations can be defined by clients, the system make it possible to store these additional typologies of relations and facets and to discover them.
• Facet and Relation instances can have additional properties which are not defined in the schema (henceforth schema-mixed mode).
• On relations:
  • Any relation has a direction, i.e. a "source" (out bound of the relation) and a "target" (in bound of the relation). Anyway, the relation can be also navigated in the opposite direction;
  • It is not permitted to define a Relation having a Facet as "source". In other words:
    • It is not permitted to define a Relation connecting a Facet with another one;
    • It is not permitted to define a Relation connecting a Facet with a Resource (as target);
  • A Facet instance can be linked (by ConsistsOf or any specialization of it) from different Resources.

We derived the term Facet directly from the dictionary definition. Merriam Webster Dictionary defines facet as “any of the definable aspects that make up a subject (as of contemplation) or an object (as of consideration)”^[1]. The Free Dictionary defines a facet as “One of numerous aspects, as of a subject” ^[2].

Type Attributes

Any attribute defined in the type schema is characterised by:

• Name : Property Name
• Type : The Type of the Property (e.g. String, Integer, ...). It can be a Basic Type or a Derived Type or a Complex Type
• Description : The description of the Property. default=null.
• Mandatory (M): Indicate if the Property is mandatory. default=false.
• ReadOnly (RO): The Property cannot change its value. default=false.
• NotNull (NN): Whether the property must assume a value diverse from 'null' or not. default=false
• Max (Max): default=null
• Min (Min): default=null
• Regex (Reg)): A Regular Expression to validate the property value, default=null. A good online tool for regex is avalable at https://regex101.com/

Basic Types

Derived Types

The following are obtained using a String as real type and adding a validation regex.

Complex Types

Any property defined by composing basic types, complex types and other complex types. Any complex type can be defined by extending Property type.

Property

It does not define any field. It is just used as a base class.

The Java Interface declaration for such a type is available at:

https://code-repo.d4science.org/gCubeSystem/information-system-model/src/branch/master/src/main/java/org/gcube/informationsystem/model/reference/properties/Property.java

Header

Every Entity and Relation has an Header automatically created/updated by the System.

The Java Interface declaration for such a type is available at:

https://code-repo.d4science.org/gCubeSystem/information-system-model/src/branch/master/src/main/java/org/gcube/informationsystem/model/reference/properties/Header.java

PropagationConstraint

At any time entities and relations can be added or removed to/from a context or deleted. The PropagationConstraint property contained in each relation is a predefined Property type which indicates the behaviour to be held on a target entity when an event related to a context occurs in the source resource or directly to the relation.

Remove values;

• cascadeWhenOrphan: When a remove action is performed on the source Entity of the relation, or directly on the relation, then the same remove action apart on the relation is performed to the target entity if it has no other incoming relations.
• cascade: When a remove action is performed on the source Entity of the relation, or directly on the relation, then the same remove action is performed on the relation and its target entity.
• keep: When a remove action is performed on the source Entity of the relation, or directly on the relation, then the same remove action is performed on relation but never to the target entity.

Add values;

• propagate: When an 'add' action is performed on the source Entity of the relation, or directly on the relation, then the same add action is performed on the relation and its target Entity.
• unpropagate: When an 'add' action is performed on the source Entity of the relation, is performed on source relation only. Trying to perform an 'add' action on the relation has no effects.

Any Relation contains such a property. If the values are not specified at creation time the system initialize it with the following rules:

• ConsistsOf Relation : remove=cascade, add=propagate
• IsRelatedTo Relation : remove=keep, add=unpropagate

The Java Interface declaration for such a type is available at:

https://code-repo.d4science.org/gCubeSystem/information-system-model/src/branch/master/src/main/java/org/gcube/informationsystem/model/reference/properties/PropagationConstraint.java

Encrypted

The Java Interface declaration for such a type is available at:

https://code-repo.d4science.org/gCubeSystem/information-system-model/src/branch/master/src/main/java/org/gcube/informationsystem/model/reference/properties/Encrypted.java

Entity

The Java Interface declaration for such a type is available at:

https://code-repo.d4science.org/gCubeSystem/information-system-model/src/branch/master/src/main/java/org/gcube/informationsystem/model/reference/entities/Entity.java

Resource

The Java Interface declaration for such a type is available at:

https://code-repo.d4science.org/gCubeSystem/information-system-model/src/branch/master/src/main/java/org/gcube/informationsystem/model/reference/entities/Resource.java

Facet

Early ideas and thinking on facets were documented at 2nd Generation Resource Model: Facets

Facets are collections of attributes conceived to capture a certain feature/aspect of the Resource they are associated with. Every facet can define zero or more properties. Besides the per-facet envisaged properties, clients can add new ones.

The Java Interface declaration for such a type is available at:

https://code-repo.d4science.org/gCubeSystem/information-system-model/src/branch/master/src/main/java/org/gcube/informationsystem/model/reference/entities/Facet.java

Relation

Every relation has:

• An Header
• A PropagationConstraint
• Zero or More properties (not necessarily predefined, similarly to Facets).

The Java Interface declaration for such a type is available at:

https://code-repo.d4science.org/gCubeSystem/information-system-model/src/branch/master/src/main/java/org/gcube/informationsystem/model/reference/relations/Relation.java

IsRelatedTo

The Java Interface declaration for such a type is available at:

https://code-repo.d4science.org/gCubeSystem/information-system-model/src/branch/master/src/main/java/org/gcube/informationsystem/model/reference/relations/IsRelatedTo.java

ConsistsOf

The Java Interface declaration for such a type is available at:

https://code-repo.d4science.org/gCubeSystem/information-system-model/src/branch/master/src/main/java/org/gcube/informationsystem/model/reference/relations/ConsistsOf.java

Internal Entity and Relation

For internal use only are defined the following entity and relation:

• Context
• IsParentOf

Context

Model a Context (aka scope) in the same Application Domain.

IsParentOf

This relation has no propagation constraint.

Best practices and guidelines

• On Facet instances "reuse" across Resource Profiles:
  • This can be guaranteed automatically by the system, if and just in the case the system wants to avoid duplication of information. It is based on a configuration policy;
  • This MUST be done only when a change in a facet instance MUST affect a change in all Resources connected to such a Facet.

Maven coordinates

To use the Java library containing the classes modelling the IS Model you can declare the following dependency:

<dependency>
	<groupId>org.gcube.information-system</groupId>
	<artifactId>information-system-model</artifactId>
	<version>[5.0.0,6.0.0-SNAPSHOT)</version>
<dependency>

gCube Model

1. ↑ https://www.merriam-webster.com/dictionary/facet
2. ↑ https://www.thefreedictionary.com/facet