diffenrece between Propertie, values and references

[Hatime Bencharqui]

hi, 

this is my first time in this forum,

my question:

I cant understand the différence between Propertie, values and references,

some exemples use properties athers use vlaues, are they the same.

I need some exemples how we can use both values and properties 

Thanks

[Remy Fannader]

Individuals (objects or running activities) have a continuous identity within some address space. They are characterized by properties defined on their own (size, price,...) but valued when associated to specific individuals ($10, 100 sqf, ...), references are properties whose value point to individuals.

https://caminao.wordpress.com/what-who-how-when-where/what-is-to-be-represented/domains/features/

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[Hatime Bencharqui]

thank you very much

[Hatime Bencharqui]

thank you very much M. Remy 

2016-12-20 9:44 GMT+01:00 Hatime Bencharqui <bench...@gmail.com>:

thank you very much

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Hatime BENCHARQUI
GSM: 06 62 04 12 72 

[Jorge Maxit]

Hatime,

Attached there is a simple example that may help you with the meaning of the words "property or properties"and "references".

The color of the car body is called an attribute (not a property) or "value."  Also, the motor power is a "value".

Start(), Stop(), etc., are called "operations".

The black diamond relates two blocks, one of which (the child) is the property of another (the parent).  

A white diamond relates two blocks, but they don't form an integral part, and one of them is called a "reference" (such as the charging station)

A white triangle denotes a choice.  the block above the triangle is called an "abstract" block, and the name is usually written in italics. 

Hope this helps with your understanding of the meaning of these words in SysML.

Jorge

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[JM]

Remi,

I would avoid the use of the word property to mean "values", such as price, weight, etc.  

The word "property" is generally used to denote the relationship between a child block and a parent block, that is, the child being the "property" of the parent, and shown with a black diamond pointing from the child to the parent.  

Jorge

On Tuesday, December 20, 2016 at 4:12:31 AM UTC-6, Remy Fannader wrote:

Individuals (objects or running activities) have a continuous identity within some address space. They are characterized by properties defined on their own (size, price,...) but valued when associated to specific individuals ($10, 100 sqf, ...), references are properties whose value point to individuals.

https://caminao.wordpress.com/what-who-how-when-where/what-is-to-be-represented/domains/features/

On 18 December 2016 at 23:00, Hatime Bencharqui <bench...@gmail.com> wrote:

hi, 

this is my first time in this forum,

my question:

I cant understand the différence between Propertie, values and references,

some exemples use properties athers use vlaues, are they the same.

I need some exemples how we can use both values and properties 

Thanks

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[Remy Fannader]

Jorge,

To begin with, I didn't use the word "property" for value; then, the term "property" is often used for "attribute" even if it includes also operations in SW design context. Third, definitions are not given but should be considered as conceptual tools to be assessed with regard to purposes.

https://caminao.wordpress.com/about/reflections-for-the-perplexed/

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[Hatime Bencharqui]

thank you mr. Jorge for your explanations, 

[Dan George]

Wow, Remy's statements are always concise but I rarely understand them. This one, however, was concise and I thought it was clear, as well. Something like price or weight is a value type? A property can be of value type or of reference to something that has identity. A value type is something that has a value that is not a "pointer", "link" or reference to some other thing.

MJ, are you saying that property and attribute are not synonyms? Seems like you are saying that in SysML, property and reference are synonyms and attributes are always of value type.

I'd be grateful for more discussion that would clarify how Remy's statement (which I had thought was very clear).

[Tom Pender]

Hi Hatime,

In SysML a block defines the pieces of information that describe the block or that the block knows.

SysML blocks use three types of information, value property,  reference property, and part property. In an instance of block, each slot (an instance of a property) will have a value.

A value property will contain a data type such as such as Integer or Volts.

For example our Car block has a value property named "city_mileage". In one car (an instance of Car) the city_mileage = 17. In another car, city_mileage = 25. When you "get" the value of city_mileage you get 17 or 25.

A reference property represents one end of an association or an aggregation. In each instance the reference property will contain the memory address of the instance at the other end of a link.

For example, our Car has a reference property named "originating_Factory" of type "Factory" (another block) that is at the other end of a link. The value of this property is a memory address. When you "get" the value it will return an instance of Factory. For example, in one car, originating_Factory has a value of "Plant #1". In another car the factory was "Plant #2". When you "get" the value of originating_Factory you Plant #1 or Plant #2.

Footnote: In code these will look the same. But the intent is to use a referenced object as a member of a collection of objects manged by the aggregate. The parts should only be accessed directly by the aggregate object to insure that the collection or group behaves correctly. Other objects have to talk to the aggregate. The same goes for parts (below) but the aggregate object does not own the part. This is often used for logical aggregates such as a "Project_Team" with members where any member Employee can participate in multiple teams at the same time or over time. The problem is that programming languages do not handle aggregation.

A part property works the same as a reference property but can only be used in a composite block.. The part property has the address of a block that is owned and managed by a composite block. (The part object cannot exist apart from the composite object.) For example, our Car block defines a part property named "engine" of type "Engine". In a car, the value would be the address for an instance of "Engine". As in aggregation, a "get" will return an instance of Engine.

I hope this helps.

Tom

[Remy Fannader]

First, properties (aka features) are types used to characterize individuals (objects or phenomena). As a corollary they can only be instanciated (aka valued) when associated to identified individuals. That understanding should not depend on any method or tool.

Second, if characteristics are to be defined independently of values implementation (stored, computed, referenced), the term "property" should cover attributes, operations, and references.

Third, if references are to be used before more can be said about integrity constraints, the term "reference" should cover associations as well as parts.

https://caminao.wordpress.com/how-to-implement-symbolic-representations/patterns/functional-patterns/connector-patterns/

PS. Thanks @Dan, I really appreciate.

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[JM]

Remy,

After reading again my previous email I realized that:

1. I was using terminology of the tool I use, rather than standard SysML definitions. 

2. I used a tone as if I was giving you a tutorial on a subject that is not my area of expertise.

3. I misspelled your name.

I feel sorry and I apologize,

Jorge

[Stephan Roth]

Hello Hatime,

the term "Property" is sometimes puzzling to those who are new to SysML respectively UML. Furthermore, different modeling tools are depicting them in diagrams in different ways. For instance, sometimes the block compartment for values is captioned with "values", and sometimes with "value properties".

First of all, Property is a UML «metaclass» (i.e. a class of the UML meta model) that is derived from abstract «metaclass» StructuralFeature. There is a composition relationship between a Class and zero-to-many Properties, whereby the role name at the association end connected with the Property is "ownedAttribute". From this is following that if one is speaking about attributes of a class, he/she actually means properties of that class which are in the role of the attributes.

For the SysML, numerous stereotypes were defined on the UML «metaclass» Property, for instance: DistributedProperty, ParticipantProperty, ConnectorProperty, FlowProperty. In addition, there are already further specializations of the «metaclass» Property in the UML meta model, such as, for example, «metaclass» Port. As a consequence, the SysML ProxyPort or FullPort are properties as well.

However, long story short: Nearly everything that can appear in one of the compartments of a SysML Block can be considered a Property. Values, references, parts, flow properties, constraints, ports, ... are at the end of the day all properties.

Hope that helps!

With kind regards,

Stephan Roth

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[Пу́шкин Xerophyt]

In the book of Friedenthal, it is called initialvalues. I  tried to follow the same approach, but in EA I got so far that it is called properties.

I am confused, can someone help, if this is the right approach?

[Keith Smith]

its useful to understand that there are:

1.  Classifications of things like a Block which defines a car., or blocks which define wheels

2. usage of things, like the car block using four wheels.  the four wheel usages can be containment (part of the car block) or by reference (used by the car block)

3. Instances of things, like my car in the parking lot which is an instance of the car block and also contains four instances of the wheel block

Now suppose the wheel block defines a tire pressure property.  this could be represented as a simple valueType.

This tire pressure Initial value can be specified.  The initial value is used to initially set the tire pressure "slot" for each instance of a wheel block.

However, the tire pressure "slot" in a wheel instance can be overridden with any acceptable value.

Thus if the initial tire pressure value is 32 psi, but my car has a flat tire, then one wheel instance has a tire pressure slot value of 0 psi.

Many sysML uses miss the fact that a Block and its properties are a definition of something, and not an instance.  In parametrics or other analysis you need to work with instances.

Don't treat initial values as if they are variables.

I hope this helps a little,

Keith

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[jozsef bedocs]

Hi Xerophyt.  I understand your confusion and thank you for raising the question.  Each tool developer has their own interpretation and solution; the differences in appearance and verbiage can be confusing.  I cannot tell for certain the kind of diagram from the posted partial example; but it appears to be a Block Definition Diagram (BDD) vs the Internal Block Diagram (IBD) from Friedenthal's book.  You have accomplished an equivalent difference though the meaning may not be apparent.  Defining initial values on a BDD means that all objects (instances) will have these initial values.  Defining initial values in an IBD means that only this object has these values.  

I hope this provides some clarity.

Best,

Jozsef

[Пу́шкин Xerophyt]

Thanks Jozsef,

both examples are in IBD.

Actually, i still have trouble to understand, when to use :properties or when to use :values.

Thanks for any hint :)

BEst

[Пу́шкин Xerophyt]

Hello Joszef,,

i am using EA v15. When would you recommend to use values or properties? Additionally EA offers to drop elements as Attributes , Properties and Properties(part).

1) I would like to describe which Operating System or Broker Address is used.

2) Than I would like to inherit the behaviour "subscribe" and "publish".

Hope , you can give me some advices.

Am Donnerstag, 9. Juli 2020 19:03:56 UTC+2 schrieb jozsef bedocs:

[jozsef bedocs]

Hi.  

Thank you for the followup.  

Values and Properties characterize a Block.  A characterization could be data that is sent or received.  Data may require further elaboration (etc., min value, max value, resolution, accuracy, units ...)  

Values use a classifier called a DataType.  If the DataType does not need further elaboration in the model, then Values can be used.  DataType does not support having relationships or properties; so, if you need to elaborate data, the Property needs to be used.  Property can be classified to Blocks which provides all of the richness of properties and relationships.  

Best of luck.

[jozsef bedocs]

Hi.  

SysML is a rich language and usually multiple solutions exist.  The language provides for inheritance; however, it is often overly used.  I use inheritance only when forced to do so. 

In the specific case that you describe, publish/subscribe is more a property of interface behavior.  One possible solution would be to use a full port that is classified to an Interface Block.  The Interface Block would contain the behaviors for publish and subscribe.  To learn more, read chapter 7.6 in Friedenthal's book.  

Hope this helps.

Best,

Jozsef