=Paper=
{{Paper
|id=Vol-2542/MOD20-TuD3
|storemode=property
|title=Advanced Features for Model Visualization in the UML and OCL Tool USE
|pdfUrl=https://ceur-ws.org/Vol-2542/MOD20-TuD3.pdf
|volume=Vol-2542
|authors=Martin Gogolla,Haleh Havakili,Carsten Schipke
|dblpUrl=https://dblp.org/rec/conf/modellierung/GogollaHS20
}}
==Advanced Features for Model Visualization in the UML and OCL Tool USE==
https://ceur-ws.org/Vol-2542/MOD20-TuD3.pdf
Joint Proceedings of Modellierung 2020 Short, Workshop and Tools & Demo Papers
Modellierung 2020: Tools & Demo Papers 203
Advanced Features for Model Visualization
in the UML and OCL Tool USE
Martin Gogolla,1 Haleh Havakili,2 Carsten Schipke3
Abstract: The tool USE (UML-based Specification Environment) offers functionalities for UML
model validation, verification and exploration. The tool supports to describe system structure and
behavior with class models, protocol state machines and imperative operation implementations on
the modeling level, utilizing OCL constraints (a) for class and state invariants as well as (b) for
operation and transition contracts. Validation and verification relies on the construction of object
model snapshots. This contribution focuses on advanced visualization features that have recently
been developed for object models. Using these new features, it is now feasible (a) to take advantage
of various automatic layout options for object models and (b) to express advanced views on object
models concentrating not only on classes but utilizing also associations.
Keywords: UML; Class model; Object model; Object model visualization features
1 Introduction
The tool USE (UML-based Specification Environment) [US20] offers essential functionali-
ties for model validation, verification and exploration of UML and OCL models. The tool
allows the developer to catch system structure and behavior with class models, protocol state
machines and operation implementations on the modeling level, utilizing OCL expressions
(a) for class and state invariants, (b) for operation and transition contracts and (c) for
imperative operation implementation on the model level [GBR07, GHD18]. Recently, USE
has added new options for object models, i.e., object diagrams, that comprise (a) automatic
layout options and (b) advanced views based on associations, in addition to views based on
classes available formerly.
The automatic layout options allow the developer to choose from various basic layout
forms (horizontal, vertical, swimlane) with variations (e.g., top to bottom, left to right). The
automatic layout is parameterized by interactive settings for horizontal and vertical object
distances. The automatic layout is applied only to objects and links visible at the time when
the automatic layout is called and thus interacts with options for building views discussed
below. For the layout, links are interpreted as being directed, and the direction (e.g., top to
bottom) and with this the placement of objects follows the specification in the textual USE
class model in which the roles from an association are declared in a particular order.
1 University Of Bremen, Database Systems, Germany gogolla@uni-bremen.de
2 University Of Bremen, Database Systems, Germany havakili@uni-bremen.de
3 University Of Bremen, Database Systems, Germany schipkca@uni-bremen.de
Copyright © 2020 for this paper by its authors.
Use permitted under Creative Commons License Attribution 4.0 International (CC BY 4.0).
204 Martin Gogolla, Haleh Havakili, Carsten Schipke
Building views in an object model, i.e., the process of hiding objects and links and optionally
successively showing them again, is now supported by utilizing associations. Links from
particular associations can now systematically be hidden and displayed again, whereas
formerly this was possible only for objects from particular classes. Furthermore, links of a
particular association kind (compositions, aggregations, whole-part associations, association
classes, reflexive associations, n-ary associations, ...) can be systematically considered
and handled together. Displayed objects can be divided into important and for a particular
purpose less important objects by showing the less important objects in a different color in
contrast to colouring for prominent objects.
In our approach, object models play a central role within the validation and verification
process, for example to show (counter) examples for suspected properties like model
consistency or invariant independence. Therefore powerful features for visually catching
important aspects and easy applicability of them are of crucial importance in our approach.
The object model options that are now available in USE seem to us more flexible and
expressive than the possibilities available in comparable approaches for object model and
instantiation visualization like Alloy [Ja19], EMF2CSP [Go12] and EMF [SBP08].
2 Recent USE Extensions and Improvements for Visualization
Figure 1 shows a first USE screenshot in which the new options for automatic object layout
are demonstrated. The class model (A) describes political parties that can participate in
elections for an area that is divided into certain districts, as shown in the figure center. The
voting result is recorded with an association class that (as usual in Germany) distinguishes
between the number of first votes (for a candidate of a party) and second votes (for the
party itself). Both Party and District objects show in derived attributes the accumulated
sum of first and second votes for the Party and District, respectively. For example, the
top-most Voting link-object in the object model in the left reflects that the (liberal) party
‘FDP’ received in the German federal state Hessen (HE) in year 2017 during the election for
the Bundestag about 238.000 first votes (number of votes given in 1000 votes), ‘FDP’ in
Germany received in total about 3.241.000 votes, and in Hessen about 3.262.000 people
casted a first vote ballot. The default, clumsy object model (B) in the top middle together
with the ‘Object count’ and ‘Link count’ windows (C) in the top right reveal that 118 objects
are present (16 Districts=FederalStates + 6 (main) Parties + 96=16*6 Votings). From these
118 objects the ones connected to Hessen are selected through the ‘Selection by OCL
expression’ window (D), and these objects are automatically layouted with the ‘Horizontal
layout’ and the indicated spacing parameters (E). The result (F) is displayed in the left
‘Object diagram’ window. Additionally the Voting objects have been selected and are shown
in light gray in order to put emphasis on the Party objects and the single District object.
Advanced UML Model Visualization Features 205
Fig. 1: New USE object model features for automatic layout and view handling (A).
206 Martin Gogolla, Haleh Havakili, Carsten Schipke
Fig. 2: New USE object model features for automatic layout and view handling (B).
Advanced UML Model Visualization Features 207
Figure 2 pictures a second USE screenshot emphasizing the new options for building
object model views. The class model (A) describes a social network with a Friendship
connection between Person objects. It has features for creating and commenting postings,
and two invariants restrict the allowed object models. The automatically generated object
model (see [GHD18] for details on the generation concepts) is shown with two different
object diagram views that focus on different aspects of the model: the Friendship aspect and
the PosterPosting resp. Commenting aspect. The two different diagrams have been achieved
(B) by visualizing only the Friendship links and (C) by visualizing only the PosterPosting
and Commenting links; both diagrams have utilized an automatic layout whose concepts
have been discussed before. The newly added USE options (D) allow the developer, for
example, that in the lower object diagram the shown links (PosterPosting and Commenting)
could be hidden and that the hidden links (Friendship) could be shown.
Object model usage: In order to emphasize the import role of object models in our setting,
let us sketch invariant independence (each single invariant cannot be deduced from the other
invariants; details see [GHD18]): As the two invariants in Fig. 2 are independent, USE
supports proving independence by automatically calculating two object models (not shown
here); one in which the 1st invariant holds and the 2nd invariant fails; and one in which the
1st invariant fails and the 2nd invariant holds.
3 Conclusion
We have demonstrated how the UML and OCL modeling tool USE has been extended and
improved recently by new visualization features for automatic object model layout and for
building sophisticated object model views utilizing associations and links.
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