How to model "virtual" attributes and methods in UML

[Larry Hayashi]

I posted this on the enterprise.general list as well but thought it might
be more appropriate here:

I was wondering if anyone out there with experience in UML could help me
with
the following problem:

In our old OO modeling paradigm we had what we called virtual attributes
on classes. These were attributes that could be calculated on the basis of
values of other attributes, associations and attribute values on classes
related by association. . This kind of attribute does not physically store
information, but calculates information whenever it is accessed. For example,
in a OO system of people in a community, children, brothers, sisters, and
grandparents can be virtual attributes since they can be calculated by the
system based on the mother and/or father attributes. In our implementation,
a virtual attribute was to never change the state of the database. It simply
made a calculation and returns one or more objects.

In our older system, we also had methods. Methods changed the state of the
database. Examples of methods in the above example might include "deletePerson",
etc.

So here's my question. In UML, I just want to model the names of and description
of certain virtual attributes and methods. I don't want to code them as that
will be implementation specific. I presume that the equivalent of virtual
attribute in UML is an operation but I am not sure. And I am not sure if
a method would also be an operation. I believe so for both. Some confirmation
would be reassuring.

Thanks for any guidance given!

Larry

[Larry Hayashi]

I've been playing around with operations since I wrote my first post yesterday.
They do not seem to have all the properties I need to define. For example,
if I have a virtual attribute of "siblings", I would look to parents attribute
and find out through backreferences who the other children of those parents
are. I might want to calculate these as ordered ...from oldest to youngest
sibling. It seems to me that this more like an association but the data is
not stored. Is there a way to represent this in UML?

Thanks again for guidance you might have!

Larry

"Larry Hayashi" <larry_hayashi@hotmail.com> wrote:
>
>I posted this on the enterprise.general list as well but thought it might
>be more appropriate here:
>
>I was wondering if anyone out there with experience in UML could help me
>with
>the following problem:
>
>In our old OO modeling paradigm we had what we called virtual attributes
>on classes. These were attributes that could be calculated on the basis
of
>values of other attributes, associations and attribute values on classes
>related by association. . This kind of attribute does not physically store
>information, but calculates information whenever it is accessed. For example,
>in a OO system of people in a community, children, brothers, sisters, and
>grandparents can be virtual attributes since they can be calculated by the
>system based on the mother and/or father attributes. In our implementation,
>a virtual attribute was to never change the state of the database. It simply
>made a calculation and returns one or more objects.
>
>In our older system, we also had methods. Methods changed the state of the
>database. Examples of methods in the above example might include "deletePerson",
>etc.
>
>So here's my question. In UML, I just want to model the names of and description
>of certain virtual attributes and methods. I don't want to code them as
that
>will be implementation specific. I presume that the equivalent of virtual
>attribute in UML is an operation but I am not sure. And I am not sure if
>a method would also be an operation. I believe so for both. Some confirmation
>would be reassuring.
>
>Thanks for any guidance given!
>
>Larry
>

[Tim Ellison]

Just a suggestion, but in the analysis model, you could do the following:

use the stereotype "<virtual property>" or simply "<virtual>". Doing this,
it needs to be well understood by your team what this stereotype implies.



"Larry Hayashi" <larry_hayashi@hotmail.com> wrote in message
news:3c470541$1@147.208.176.211...
>
> I've been playing around with operations since I wrote my first post
yesterday.
> They do not seem to have all the properties I need to define. For example,
> if I have a virtual attribute of "siblings", I would look to parents
attribute
> and find out through backreferences who the other children of those
parents
> are. I might want to calculate these as ordered ...from oldest to youngest
> sibling. It seems to me that this more like an association but the data is
> not stored. Is there a way to represent this in UML?
>
> Thanks again for guidance you might have!
>
> Larry
>
> "Larry Hayashi" <larry_hayashi@hotmail.com> wrote:
> >
> >I posted this on the enterprise.general list as well but thought it might
> >be more appropriate here:
> >
> >I was wondering if anyone out there with experience in UML could help me
> >with
> >the following problem:
> >
> >In our old OO modeling paradigm we had what we called virtual attributes
> >on classes. These were attributes that could be calculated on the basis
> of
> >values of other attributes, associations and attribute values on classes
> >related by association. . This kind of attribute does not physically
store
> >information, but calculates information whenever it is accessed. For
example,
> >in a OO system of people in a community, children, brothers, sisters, and
> >grandparents can be virtual attributes since they can be calculated by
the
> >system based on the mother and/or father attributes. In our
implementation,
> >a virtual attribute was to never change the state of the database. It
simply
> >made a calculation and returns one or more objects.
> >
> >In our older system, we also had methods. Methods changed the state of
the
> >database. Examples of methods in the above example might include
"deletePerson",
> >etc.
> >
> >So here's my question. In UML, I just want to model the names of and
description
> >of certain virtual attributes and methods. I don't want to code them as
> that
> >will be implementation specific. I presume that the equivalent of virtual
> >attribute in UML is an operation but I am not sure. And I am not sure if
> >a method would also be an operation. I believe so for both. Some
confirmation
> >would be reassuring.
> >
> >Thanks for any guidance given!
> >
> >Larry
> >
>