## 3 The SemDaServ Approach
### Artifacts
#### 3.3.4 Data and Information Models  
SemDaServ uses diagrams and modeling elements of the SysML language to model the information and data requirements. The data model is based on the information model and therefore uses the same SysML diagrams. The difference between information models and data models is in the object of study. However, the representation and modeling approach is identical--except for minor differences outlined below. The central element of the data specification is the block definition diagram: This is used to build both the information model and data model. The basic elements of the information model are shown in Figure 11: The SysML element entitled Information Item is at the center of the information flow of the Producing element block (e.g., a sensor) and the Consuming element block (usually a software component of the smart service). These two blocks are linked to the Information Item by the SysML element of Information flow. The information contained in the information flow is modeled by a textual description of the Information Item. The quality requirements for the information are stored as free text by the SysML note element Description. This results in an information flow from the Producing element (source) to the Consuming element (target). This can be a one-to-n relationship, which can be represented by additional information flows of an Information Item additional Consuming elements. The data model results from resolving the Information Items of the information model. The Information Item is replaced by a direct information flow linked to the data variable of the producing and the consuming elements. The variables are modeled as attributes of the blocks. If the information described in the Information Item can be completely covered by one variable, the information flow is modeled at the variable level (by direct linking of the variable using the SysML element Information flow). If several variables are required to realize the information flow, an Information Flow is modeled between the Producing element and Consuming element blocks. The basic elements of the data model are shown in Figure 12. The placeholder <no type> represents arbitrary data types. To resolve the Information Item, the information quality must also be broken down to the data quality. For this purpose, SemDaServ uses the SysML note element Description similarly as in the information model, but in this case, this element is directly linked with the variables. Thus, the data quality is described for each variable. The description of the data quality follows the scheme described in Figure 10. To increase the clarity of all information models and data models, the Note elements can be modeled outside the diagram by using a model-oriented tool. If these initial modeling possibilities are not sufficient in a particular use case, the information model and the data model can be supplemented by additional UML and SysML diagrams: sequence diagrams, for example, can be used to model time-dependent relationships. The use of use case diagrams can help in understanding the use case when the business model description, as well as the product and service structure, are too complex, too complicated, or too superficial from the perspective of the actors involved. The use case diagram can then be used to focus on the essentials--especially from the user perspective. If a large number of detailed quality descriptions arise and/or exhibit a large number of mutual dependencies, the information and data quality descriptions can be combined in a requirement diagram, linked to the associated blocks, and modeled to take these dependencies into account. If it turns out during the data  
Figure 11: Information model. Figure 12: Data model. a block (e.g., an assembly of the SSS, represented as a block in the data model) needs to be considered in more detail, the corresponding block can be linked to an internal block diagram and described in detail.