Software product line (SPL) is a software engineering paradigm for software development. A software product within a product line often has specific functionalities that are not common to all other products within the product line. Those specific functionalities are termed “variant features” in a product line. SPL paradigm involves the modeling of variant features. However, little work in SPL investigates and addresses the modeling of variant features specific to user interface (UI). Unified Modeling Language (UML) is the de facto modeling language for object-oriented software systems. It is known that UML needs better support in modeling UIs. Thus, much research developed UML extensions to improve UML support in modeling UIs. Yet little of this work is related to developing such extensions for modeling UIs for SPLs in which variant features specific to UI modeling must be addressed. This research develops a UML extension -Web User Interface Modeling Language (WUIML) to address these problems. WUIML defines elements for modeling variant features specific to user interfaces for Web-based SPLs. The model elements in WUIML extend from the metaclass and BasicActivity of the UML2.0 metamodel. WUIML integrates the modeling of variant features specific to user interfaces to UML. For example, in a Web-based patient registration software product line, member products targeting British users may use British date format in the user interface, while member products targeting United States users may use United States date format in the user interface. Thus, this is a variant feature for this product line. WUIML defines a model element, XOR, to represent such exclusive or conditions in a product line user interface model. WUIML would reduce SPL engineers’ efforts needed in UI development. To validate the WUIML research outcome, a case study was conducted. The results of this empirical study indicate that modeling UIs for Web-based SPLs using WUIML is more effective and efficient than using standard UML.
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Software product line (SPL) (Chastek, Donohoe, Kang, & Thiel, 2001; Clements & Northrop, 2002; SEI, 2005a) is a software engineering paradigm to develop software products. One important step in the SPL paradigm is the modeling of the functional features of software products across the product line. The features are called common core. An even more important step in the SPL paradigm is the modeling of the specific functional features within a particular member product in a product line. These specific functional features are called variant features because they are the features that differentiate member products in the product line. Then based on the model, a product is ‘assembled’ by reusing the common core and selected variant features.
Unified Modeling Language (UML) (OMG, 2003b, 2004) (Rumbaugh, Jacobson, & Booch, 2005) is a standard object-oriented modeling language. UML includes multiple views and diagram types to capture software functionalities from user perspective. However, UML seems to have not been developed for modeling user interface specific issues (Kovacevic, June 1998; Silva & Paton, 2003). One of the usages of user interface models is that in model-based user interface management systems (MB-UIMSs) (Pedro A. Szekely, Piyawadee Noi Sukaviriya, Pablo Castells, Jeyakumar Muthukumarasamy, & Salcher, 1996; Tony Griffiths et al., September 1999), user interface models can be used to generate user interface codes. There are extensions of UML (Blankenhorn & Jeckle, 2004) (Nunes, 2003) (Silva, 2002) to make UML better support user interface modeling. Yet these extensions often assume the modeling of a single system instead of a SPL. On the other hand, although standard UML (OMG, 2003b, 2004) seems to have not been developed to support the modeling of SPLs, there are works (Gomaa, 2004; Gomaa & Gianturco, 2002; Tewfik Ziadi, Loïc Hélouët, & Jézéquel, May 2004) on extending UML to improve UML supports in modeling SPLs. Yet these works do not focus on user interface modeling. Currently, many software products are Web-based. However, some (Silva, 2002) observe that there are specific modeling challenges for modeling user interfaces of Web-based software systems.
Thus, it is not clear how to model variant features for user interface specific issues in Web-based software product lines. This is an important barrier to overcome if software product line development of Web-based products is to take greater advantage of software reuse objectives: increased quality, decreased effort, or decreased time to market. Therefore, this paper is concerned with reporting research about developing a UML extension, Web User Interface Modeling Language (WUIML) that decreases effort by increasing effectiveness and efficiency needed in using UML to model user interfaces for Web-based software product lines. User interface development has been found (Myers, 1989) to account for a significant amount of overall software development work. WUIML would improve SPL software engineering paradigm in the user interface development perspective by reducing engineers’ efforts needed in user interface modeling.