02.193GPPRelease 1999Stage 1Subscriber Identity Module Application Programming Interface (SIM API)TS
The SIM API shall consist of APIs for 3GPP TS 11.14  (pro-active functions) and 3GPP TS 11.11  (transport functions). Figure 3 illustrates the interactions between these APIs.
Figure 3: SIM API Architecture
In this model, the GSM data field structure is viewed as a series of data structures and data access functions to the API. In the physical model of course, they may still be stored in elementary files, but the functions will access these data as values within those data structures.
The following figure mirrors the SIM API architecture, relating each part to the appropriate ETSI/GSM or ISO/IEC specification.
Process ( A series of instructions requiring Toolkit commands and variables )
3GPP TS 03.48 
Transport Security Mechanisms (e.g. applied to SMS Data download)
3GPP TS 11.14 
TLVs (Built from commands and variables)
3GPP TS 11.11 
Transport of TLVs (Envelope, Fetch, Terminal Response)
Interaction with data (Other 3GPP TS 11.11  commands)
ISO/IEC 7816‑3 
Physical interface (e.g. T=0)
Figure 4: SIM API layers
A general requirement of the SIM API is that applets should not interfere with the basic GSM services.