# SCM-IoT: An Approach for Internet of Things Services Integration and Coordination
## 5 Discussion
### Lack of Dynamism  
CPNs are an abstract computational model that allows describing and studying the relationships between parts of a system characterized by their concurrent, asynchronous, distributed, parallel, non-deterministic, and stochastic properties. For the construction of IoT systems, CPNs support tools for modeling, visualization, analysis, validation, and verification of behaviors within a system, as they provide: hierarchical descriptions, interactive simulations, and an intuitive and attractive graphic representation. Although the abstract model in CPN allows describing the expected functionality of each service, they also have severe limitations due to the lack of sound dynamics. An example of these limitations is its inability to include logical conditions in service requests correctly interpreted at simulation time, such as passing the condition \"\(p<p^{\prime}\)\" as a parameter in an update request. The reason is that the variables \"\(p\)\" and \"\(p^{\prime}\)\" that appear in this expression do not have a denotation as parameters in the update transition U (Figure 2), since it depends entirely on the names of the variables used in the annotations corresponding entry arches. In other words, there is no way to denote a transition in CPN as a strictly evaluated function that can return zero, one, or more output values. In such denotation, the function's formal parameters may correspond to the annotations on the input arcs, and the values evaluated by the function may correspond to the annotations on the output arcs. Unfortunately, the CPNs do not impose order in the entry (and exit) places and arches. Although modern programming languages use keywords to designate formal parameters directly, CPNs do not use keywords either in the input arcs or in the input places. Finally, there is still the problem of defining an appropriate semantics for this mechanism that combines functions without side effects in the set of tokens of the CPNs. In summary, CPNs limit the expressive capacity in the dynamism of the abstract model that IoT systems require, where interoperable components can be integrated with service demands under arbitrary conditions. On the other hand, BPEL exhibits the same lack of dynamism that prevents accepting requests that include conditions of interest during the subscription. The limitations in both models impose severe limitations on the dynamism in the provision of services demanded by the IoT. A solution to solve the lack of dynamism in the provision of services lies in the possibility of compiling or dynamically interpreting the expressions included in the service provision rules. From the relational database model perspective, the SCM-IoT model notebooks can be implemented as tables and the editing services as SQL data manipulation and query language commands. Still, SQL expressions must be compiled before being executed, which could be done dynamically after subscription. However, the problem with this possible solution is that it demands more computational infrastructure for the component where the database administrator resides. However, the SCM-IoT model does not limit the dynamism to establish an interaction structure between clients and editors, making it possible to discover an editor that offers the most convenient publishing services for the client's applications. In order to find an editor offering the required services, it is possible to start by discovering the most suitable table structure for the client's application. For this purpose, the ANTARES algorithm [84] can be used to discover the table with the topics required by the application and then identify the corresponding editor. Following this approach, a natural language processing algorithm [85] can be used to build an overlay network among clients (information producers and subscribers). Advanced selection and discovery information services can also be offered in a virtual structure built on an initially unstructured environment.