Lecture #2 - Metadata Flashcards
What is Meta-Data?
The IEEE glossary says tat Metadata is “data about data”.
e.g. author of a document, the year it was published, where it published
What is the challenge in collecting Meta-Data?
Collecting metadata takes extra work and can only see the benefit when the metadata are used to facilitate further use of the resource.
There can be a long period of time between the collection and the use of metadata, and it is also often not possible to predict whether the metadata collected will be used at all.
Describe how you would model the OO-Modelling of an electric drive.
In the example, OOP must be used. A defined class of an electrical vehicle is defined.
This is very advantageous as we can just define it once and can define a system in our world.
Defining our class, we have different attributes that we define:
- Operating voltage; semantics -> AC or DC (unit V)
- Torque; semantics -> nominal torque, might not be constant (Nm)
- Serial number; Europe has standards and norms for serial number.
- Power; consuming electrical power (W)
Describe the type/instance
So, we’ve established that the class or type is the E-drive. This is how we describe the structures, characteristics and attributes of the E-drive.
We can have instances of the class, with perhaps different serial number.
- Good to re-use patterns that we have agreed on. Standardisation is very helpful.
- Efficient - Quality assurance; Is it good for the quality? Why is OOP good for meta-model itself.
- Problems can be identified in the batch.
- Good for comparing object to object, using the metadata/data sources.
- Different countries, standard in stuck.
Standardisation enhances the data itself. You get to have members from different countries, universities and companies meeting a standard -> allows quality assurance.
Describe the inheritance
Inheritance means we can have two instances of a class with different properties
The class E-drive is made with the following properties:
1. Serial number
2. Type
3. E-power
4. Year of Manufacturer
Now, we can have two different types of electric drives with the use of inheritance:
- Brush-based Electric Drive
- Communication element, which is not in every drive
- No. of brushes
- Every single attribute from the parent class
Therefore, inherited from the electric drive class.
- Brushless Electric Drive
- Type of raumer
- Type of controller
- Every single attribute from the parent class.
Something we use desperately use in meta-data.
Describe the OO Aspects in terms of Association, Aggregation, Composition.
- Association
Professor gives a lecture
- Aggregation
“A is part of B”
Gripper is part of Robot
- Composition
Once cannot exist without the other
Robot cannot exist without the control unit and e-drives.
In technical systems, what is metadata being recognised for?
It’s being recognised as attributes which help engineers classifying, understanding or searching individual instances. i.e. metadata can be used for classes and instances
Give examples of object-oriented metadata formats
Automation Markup Language (AML)
Building Information Model (BIM)
Why do we need semantics about something that is modelled in a data format?
If we have a table for example, we can use data or excel to model it. But we need to agree what the table actually is, using semantics.
When talking about the metamodel for describing information, define: Nodes
Describe resources (e.g. machines, people, objects, non-objects)
When talking about the metamodel for describing information, define: Direct edges
Describe relationships between the resources (e.g. has a parameter)
When talking about the metamodel for describing information, define: Data values
Represented in RDF by so-called literals, which can describe a resource (e.g. data point has value “20”, data point has unit of measurement “hours”.)
When talking about the metamodel for describing information, define: RDF graph
consists a set of subject-predicate-object (SPO) statements
When talking about the metamodel for describing information, define: URI
Every node and every edge needs a unique identifier
