Facet Based Resource Model

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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.

Is-model.png

Is-model-er.png

  • 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;
  • 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].


Properties

Any Property defined in the 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

Type Java type Description
Boolean java.lang.Boolean or boolean Handles only the values True or False.
Integer java.lang.Integer or int or java.math.BigInteger 32-bit signed Integers.
Short java.lang.Short or short Small 16-bit signed integers.
Long java.lang.Long or long Big 64-bit signed integers.
Float java.lang.Float or float Decimal numbers.
Double java.lang.Double or double Decimal numbers with high precision.
Date java.util.Date Any date with the precision up to milliseconds.
String java.lang.String Any string as alphanumeric sequence of chars.
Property ? extends org.gcube.informationsystem.model.reference.properties.Property This is an Object contained inside the owner Entity and has no Header. It is reachable only by navigating the owner Entity.
Property list List<? extends org.gcube.informationsystem.model.reference.properties.Property> List of Objects contained inside the owner Entity and have no Header. They are reachable only by navigating the owner Entity.
Property set Set<? org.gcube.informationsystem.model.reference.properties.Property> Set (no duplicates) of Objects contained inside the owner Entity and have no Header. They are reachable only by navigating the owner Entity.
Property map Map<String, ? extends org.gcube.informationsystem.model.reference.properties.Propertyd> Map of Objects contained inside the owner Entity and have no Header. They are reachable only by navigating the owner Entity.
Byte java.lang.Byte or byte Single byte. useful to store small 8-bit signed integers.
Binary java.lang.Byte[] or byte[] Can contain any value as byte array.

Derived Types

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

Type Java type Description
Enum java.lang.Enum or enum by default it is represented using the String representation of the Enum. So that the primitive type used will be String. The enumeration is checked by setting Regexpr property. The Regular Expression is auto-generated and it will be something like ^(FIRST-ENUM-STRING_REPRESENTATION|SECOND-ENUM-STRING_REPRESENTATION|...|LAST_ENUM_STRING_REPRESENTATION)$.

Otherwise (if indicated using an annotation), it can be represented using the Integer value of the Enum. So that the primitive type used will be Integer. The enumeration is checked using Max and Min properties.

UUID java.util.UUID String representation of the UUID. The check is obtained using the regular expression ^([a-fA-F0-9]{8}-[a-fA-F0-9]{4}-[a-fA-F0-9]{4}-[a-fA-F0-9]{4}-[a-fA-F0-9]{12}){1}$
URL java.net.URL String representation of the URL. No check actually.
URI java.net.URI String representation of the URI. No check actually.
TypeVersion org.gcube.informationsystem.utils.TypeVersion A type representing and validating a version in the following format X.X.X Major(Integer).Minor(Integer).Revision(Integer) (e.g 1.0.0, 2.3.0, 2.0.1). The check is obtained using the regular expression ^[1-9][0-9]{0,}\.(0|([1-9][0-9]{0,}))\.(0|([1-9][0-9]{0,}))$.

Complex Types

Any property defined by composing basic types derives from 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.

Header extends Property
Name Type Attributes Description
uuid UUID Mandatory=true
NotNull=true
ReadOnly=true
This UUID is be used to identify the Entity or the Relation univocally.
createdBy String Mandatory=true
NotNull=true
ReadOnly=true
The user that created the Entity or the Relation. It is initialized at creation time.
creationTime Date Mandatory=true
NotNull=true
ReadOnly=true
Creation time.
lastUpdateBy String Mandatory=true
NotNull=true
The user that made the last update to the Entity or the Relation. At creation time, it assumes the same value of creator.
lastUpdateTime Date Mandatory=true
NotNull=true
Last Update time. At creation time it assumes the same value of creationTime.


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.

PropagationConstraint extends Property
Name Type Attributes Description
remove Enum Regex=(cascadeWhenOrphan|cascade|keep) It indicates the behaviour to implement for the target Entity when a 'remove' action is performed on the source Resource. Remove actions are: (i) the operation of removing an instance from a context; (ii) the operation of deleting an instance (it has an impact on all contexts).
add Enum Regex=(propagate|unpropagate) It indicates the behaviour to implement for the target Entity when an 'add' action is performed on the source Resource. Add action is the operation of adding an instance to a context.


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:


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
Encrypted extends Property
Name Type Attributes Description
value String The encrypted value. The resource registry store safely the value. When received the value is decrypted using the key of current context and store the value safely. When the value is read, the resource-registry retrieve the value and encrypt it with the key of current context.

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

Abstract Entity
Goal: This is the base type for any entity.
Properties
Name Type Attributes Description
header Header Mandatory=true
NotNull=true
ReadOnly=true
A distinguishing string to be used by clients to identify the access point of interest.

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

Abstract Resource extends Entity
Scope: This entity is conceived to describe every "main thing" to be registered and discovered by the Information System.
Source Relation Multiplicity Target Description
Facets
Resource ConsistsOf 1..n Facet Any Resource consists of one or more Facets that describes the different aspects of the resource.
Relations
Resource isRelatedTo 0..n Resource Any Resource can be related to any other 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.

Abstract Facet extends Entity
Goal: This is the base type for any Facet.
Known Usage
Source Relation Multiplicity Target Description
Resource ConsistsOf 1..n Facet Any Resource consist of one or more Facets which describes the different aspects of the 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/Facet.java

Relation

Every relation has:

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

IsRelatedTo extends Relation
Source Relation Multiplicity Target Description
Resource IsRelatedTo 0..n Resource A relation linking any two Resources.

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

ConsistsOf extends Relation
Source Relation Multiplicity Target Description
Resource ConsistsOf 1..n Facet A relation connecting each Resource with one of the Facet characterizing it.


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

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

Context
Goal: Models a Context (aka scope).
Properties
Name Type Attributes Description
name String Mandatory=true
NotNull=true
The name of the context. Two Context with the same name can exist but they cannot have the same parent. In other words, a Context cannot have two children with the same name.
Known Usage
Source Relation Multiplicity Target Description
Context IsParentOf 0..n Context ...

IsParentOf

This relation has no propagation constraint.

Source Relation Multiplicity Target Description
Context IsParentOf 0..n Context ...

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

An example of instantiation of the IS model is the gCube Model.
  1. https://www.merriam-webster.com/dictionary/facet
  2. https://www.thefreedictionary.com/facet