Part 1 OCL Common Expressions
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   An introduction to OCL - the Object Constraint Language - through examples. This session also introduces the new MDriven Debugger
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An introduction to OCL - the object contraints language - by example.
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     <strong> Common expressions</strong>
     <strong> Common expressions</strong>
    <ul>
     <span class="navigation-item" data-video="YwNDD-jlkWw" data-start="59" tabindex="0">.create </span>
     <span class="time" data-video="DBEP3oMWsIg" data-start="54" tabindex="0">.create </span>
     <span class="navigation-item" data-video="YwNDD-jlkWw" data-start="82" tabindex="0">.allinstances</span>
     <span class="time" data-video="DBEP3oMWsIg" data-start="77" tabindex="0">.allinstances</span>
     <span class="navigation-item" data-video="YwNDD-jlkWw" data-start="280" tabindex="0">.select</span>
     <span class="time" data-video="DBEP3oMWsIg" data-start="275" tabindex="0">.select</span>
     <span class="navigation-item" data-video="YwNDD-jlkWw" data-start="623" tabindex="0">.asstring</span>
     <span class="time" data-video="DBEP3oMWsIg" data-start="618" tabindex="0">.asstring</span>
     <span class="navigation-item" data-video="YwNDD-jlkWw" data-start="1150" tabindex="0">.representation</span>
     <span class="time" data-video="DBEP3oMWsIg" data-start="1145" tabindex="0">.representation</span>
     <span class="navigation-item" data-video="YwNDD-jlkWw" data-start="109" tabindex="0">at0 and at operator</span>
    </ul>
     <span class="navigation-item" data-video="YwNDD-jlkWw" data-start="132" tabindex="0">assign operator</span>
     <span class="time" data-video="DBEP3oMWsIg" data-start="104" tabindex="0">at0 and at operator</span>
     <span class="navigation-item" data-video="YwNDD-jlkWw" data-start="115" tabindex="0">orderby</span>
     <span class="time" data-video="DBEP3oMWsIg" data-start="127" tabindex="0">assign operator</span>
     <span class="navigation-item" data-video="YwNDD-jlkWw" data-start="188" tabindex="0">orderbyDescending</span>
     <span class="time" data-video="DBEP3oMWsIg" data-start="110" tabindex="0">orderby</span>
     <span class="navigation-item" data-video="YwNDD-jlkWw" data-start="197" tabindex="0">loopvar</span>
     <span class="time" data-video="DBEP3oMWsIg" data-start="183" tabindex="0">orderbyDescending</span>
     <span class="navigation-item" data-video="YwNDD-jlkWw" data-start="265" tabindex="0">ocl editor overhaul support</span>
     <span class="time" data-video="DBEP3oMWsIg" data-start="192" tabindex="0">loopvar</span>
     <span class="navigation-item" data-video="YwNDD-jlkWw" data-start="357" tabindex="0">execution of expressions</span>
     <span class="time" data-video="DBEP3oMWsIg" data-start="260" tabindex="0">ocl editor overhaul support</span>  
     <span class="navigation-item" data-video="YwNDD-jlkWw" data-start="483" tabindex="0">union operator</span>
     <span class="time" data-video="DBEP3oMWsIg" data-start="352" tabindex="0">execution of expressions</span>
     <span class="navigation-item" data-video="YwNDD-jlkWw" data-start="536" tabindex="0"> ocl use in the model (string representation)</span>
     <span class="time" data-video="DBEP3oMWsIg" data-start="488" tabindex="0">union operator</span>
     <span class="navigation-item" data-video="YwNDD-jlkWw" data-start="635" tabindex="0"> collect operator </span>
     <span data-video="DBEP3oMWsIg" data-start="531" tabindex="0"> ocl use in the model (string representation)</span>
     <span class="navigation-item" data-video="YwNDD-jlkWw" data-start="683" tabindex="0"> member of ECOModel Root </span>
     <span class="time" data-video="DBEP3oMWsIg" data-start="630" tabindex="0"> collect operator </span>
     <span class="navigation-item" data-video="YwNDD-jlkWw" data-start="704" tabindex="0"> abstract classes and its inheritance </span>
     <span class="time" data-video="DBEP3oMWsIg" data-start="678" tabindex="0"> member of ECOModel Root </span>
     <span class="navigation-item" data-video="YwNDD-jlkWw" data-start="917" tabindex="0"> specialization .OclType </span>
     <span class="time" data-video="DBEP3oMWsIg" data-start="699" tabindex="0"> abstract classes and its inheritance </span>
     <span class="navigation-item" data-video="YwNDD-jlkWw" data-start="1121" tabindex="0"> derived attribute </span>
     <span class="time" data-video="DBEP3oMWsIg" data-start="912" tabindex="0"> specialization .OclType </span>
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     <span class="time" data-video="DBEP3oMWsIg" data-start="1116" tabindex="0"> derived attribute </span>
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Raw subtitles text
[[Category:MDriven Designer]]
 
[[Category:OCL]]
hi and welcome to the session on ocl
[[Category:OCL Editor]]
 
[[Category:Expressions]]
expressions start with a simple model
[[Category:Derivations]]
 
[[Category:Operators]]
containing of fruits orange as one
{{Edited|July|12|2024}}
 
property
 
weight type integer and gonna start a
 
system running this saving data to an xml file
 
that we save on in temp file "fruit"
 
I'm going to use the new debugger
 
so if you haven't seen this before
 
it's a good introduction to that as well
 
and the new debugger allows you to
 
write actions as long as ocl, so we
 
could do orange.create and then
 
we have actually created one orange object
 
an instance of the class, so let's
 
create some oranges and once we have them we
 
can do orange.all instances
 
which is a common ocl operator to show all
 
instances of a certain class
 
as we see the weight is 0. It's the default value for
 
integer that's not nullable
 
and we can index the list of all instances with
 
the  "at(0) operator
 
so at 0 there's also an at operator, but at(0) is
 
zero based the at operator is one based
 
so starting from zero to count minus 1
 
or length minus one
 
and let's do an action at first object at list
 
assigning the weight to 18
 
so this is the assign operator colon equals and
 
we can set the weight values
 
something like that and then we'd save,
 
now we have saved them to the xml file
 
that we stated initially and in ocl we can
 
do a lot of different operations
 
let's check out the "orderby", orderby(weight)
 
and there's also an orderby this ending
 
and in all these iterations, there
 
can be a loop variable and
 
it's separated with the pipe sign, so that's
 
what you here, the loopvar
 
it is just each object iterating
 
in the loop, so it will be of the type
 
that interested iteration, so orderDescending,
 
or orderby
 
results an operation for first and of
 
course one for last that the given a list
 
just returns one object and you can
 
combine ocl expressions
 
so order descending last
 
the ocl editor has been given an
 
overhaul to better support
 
support you as you type your expressions it's
 
not perfect and we will see some issues with it
 
but it's getting there
 
select is a common ocl operator
 
that we want to limit our results at
 
here we select on the weight larger than 20,
 
but the loop variable is optional,
 
so you do not always need it
 
all kind of comparison operators are
 
available larger than or equal etc.
 
let's add another class, apple
 
also has a weight
 
and if I do apple.all instances apple is
 
not a type name, because I need to
 
reread the model in order to have my
 
executor to know about it
 
so once I re-read and it doesn't give me
 
the error, but there are no apples of course
 
so write action: and then Apple.create
 
get two of those, five and the new debugger
 
here interprets all continuous lines
 
as one expression, so you need to
 
leave an empty roll between
 
expressions that are not supposed to
 
belong to each others
 
and of course it defaults to ocl but as soon as you
 
write action: it will do action language instead
 
which allows you to set values to operate on values to change state
 
normally ocl is totally free from side effects
 
but the action language that is unique for MDriven
 
allows you to operate objects as well
 
with the ocl syntax so we're
 
setting some weights on the apples
 
and we saved that state
 
so Apple.all instances also have the
 
oranges since before
 
these are the oranges
 
these are the apples and what we can do
 
is combine them, the operator called "union"
 
so there we are together, but we don't
 
see not very clear what they are
 
so let's add the default string
 
representation to the classes
 
this is one place where you actually use ocl
 
in the model of course you use it all
 
over the model but this is just one of
 
the places "orange with weight of
 
and then we grab our "selves" weight and append
 
grams, but since weight is an integer
 
we need to convert it to as #sString in
 
order to get use a +operator on strings
 
let's do the same thing for the Apple
 
but right Apple instead save the model
 
yes still don't see anything because we
 
haven't said that we want
 
to see it as string, the default string
 
representation on the obvious now I see them
 
what I can do is use to collect
 
operator, to build a tuple of pieces from
 
the result that I'm working on
 
so the loop variable will be one of the
 
objects in the iteration and that should
 
have weight and I can do that as string
 
if I can spell, but now we see that weigh it,
 
this is not correct weight is not a
 
member of eco model root
 
why does it say EcoModelRoot well
 
because that's the common denominator
 
between apple and orange currently,
 
so here we have discovered a need for an
 
abstraction really apple and orange are
 
really sharing things
 
we should make that available in the model
 
so that we can operate on it
 
so let's interview the abstraction
 
called fruit and we model this with the
 
generalization arrow
 
and we want to add the attribute
 
weight to fruit, but doing so we will find that there's error
 
reported on model,
 
because now orange and apple inherit weight from fruit and they
 
have fruit on their own so that's not allowed
 
but renaming it to new weight instead of weight,
 
so we can see that we get it work
 
new weight, then it's ok but of course
 
the new wa is 0, because we haven't set
 
but now we can do act on the
 
abstraction the fruit fruit.allinstansec
 
as string, that will return both
 
oranges and apples,
 
but it reports common denominator as new weight is the
 
only thing they share
 
so let's say that this is the weight and
 
there is actually no need for a unique
 
weight to apples or unique weight on oranges
 
it's just weight of the fruit
 
then we see the weight on the fruit
 
so this is why modeling is so good
 
because it works exactly as we think
 
about things in daily life, we use
 
abstractions all the time just getting
 
around life, just grabbing a chair on our
 
new office that we've never visited before
 
him instantly knowing that it
 
will work as any other chair is our ability to abstract
 
but having the fruits can we access
 
their specialization what they're
 
actually called what kind of fruit they are
 
yes, there's some ocl-type operator with
 
the type name that gives us this information
 
orange and apple, there we see, so that would
 
allow us to break out the hard-coded orange
 
to self ocl-type typename
 
remove the orange and of course if we do
 
it there we might as well
 
yeah let's, look at this first
 
orange.string is still ok, so if we can
 
do that we might as well move it up to fruit
 
going to remove it from the
 
subclasses just have it on the
 
superclass fruit, so like that, re-read
 
yay works like before but with less code or less ocl
 
the fruit is actually abstract we don't think of fruit as being
 
there's no, nothing existing just
 
being fruit is either orange or Apple in our model
 
so I mark it as abstract and
 
the class name is drawn italic instead
 
I can create apples, but I'm not supposed
 
to be able to create fruit
 
can't instantiate abstract class fruit, this
 
will help us to avoid doing illegal
 
things as our model evolves, orange I can
 
create oranges and apples but not fruits
 
that's ok and I can access fruit all instances or
 
just the oranges or just the apples
 
and I can act on fruits checking their
 
weight and I get us all the fruits
 
having a weight larger than 20 grams both oranges
 
and apples and move this or rather copy it
 
to a new attribute, attributes
 
this attribute is called presentation
 
not going to make it derived, derived
 
attribute can be backed by an derivation ocl
 
and ocl expression this is another
 
place where you commonly use ocl going
 
to set the same thing as in the default
 
string representation, but since I
 
defined it as a derived attribute might
 
as well use it in the default string representation
 
reduce the definitions,
 
re-read the model, since we changed it and
 
now when I execute I see I have a new
 
property on the object fruit called presentation
 
that works for apples and the first
 
Apple is Apple would wait 15 grams
 
let's see, if I can change its weight
 
and watch when I change the weight both
 
the derived presentation and the weight changes
 
this is an extremely large and
 
positive thing with derived attributes
 
they subscribe to every change that you
 
see in the model reduces the amount of
 
code you need to write or the amount of
 
ocl, so that was the first part of the ocl
 
I'm going to come back straight away
 
with another part continuing with
 
the same sample thank you for watching, so far

Latest revision as of 15:44, 10 February 2024

An introduction to OCL - the Object Constraint Language - through examples. This session also introduces the new MDriven Debugger and shows how to get instant results from modeling efforts.

To make your experience smooth, we set the main tags mentioned in the video to the right bar menu of this mini-player. Choose an interesting subtitle on the list and immediately get to the exact theme navigation item place in the video. Now you can pick any topic to be instructed on without watching the whole video.


Common expressions .create .allinstances .select .asstring .representation at0 and at operator assign operator orderby orderbyDescending loopvar ocl editor overhaul support execution of expressions union operator ocl use in the model (string representation) collect operator member of ECOModel Root abstract classes and its inheritance specialization .OclType derived attribute

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