Addressing Non-Functional Properties in Software Architecture using ADL

1. ASWEC 2005 Brisbane Addressing Non-Functional Properties in Software Architecture using ADL Christopher Van Eenoo Osama Hylooz Khaled Khan University of Western Sydney

2. Contents • Motivation • Current state of ADL • Proposed approach • Wright ADL • Major issues • Proposed constructs • Limitations.

3. Motivation • Software architecture reveals the aspects related to systems functionality, their collaboration, and structure • Non functional aspects are rarely addressed at the architecture level • Lack of integration between functional and non-functional aspects in the architecture • Most ADLs do not incorporate quality attributes • Software architecture needs to describe non-functional properties as well as behavioural attributes.

4. Current state • Architectural Definition Language (ADL) specifies the structural composition • Limitations of current ADL features • Non-functional properties are often too abstract and stated informally • Separation of the non-functional requirements from the functional ones is not simple • Non-functional issues are often considered as an ‘after thought’ of the development process.

5. Proposed approach • We propose some ADL constructs using a combination of Wright and CSP notations • ADLs incorporate the non-functional properties • We explore how non-functional issues could be addressed at the ADL level • Not formal yet.

6. ADL Wright • Designed around three basic software architectural elements: • Components • Interface • Ports: interactions with the environment in terms of events • Computation • What actually a component does in terms of events specified in ports • Connectors • Role: behaviour of the participants in an interaction • Glue: how the participants work together to create a composition • Configurations • Instances • Attachment: put together instances • Heavily based on CSP.

7. An example of Wright Systems name Configuration XYZ Component X-Type Port Out = ā→Out § Computation = Out.a→Computation § Component Y-Type Port In = c→Inٱ§ Computation = In.c→b→Computationٱ§ Connector Z-type Role Get = ā→Get § Role Set = c→Set ٱ§ Glue = Get.a→Set.c→Glueٱ§ Instances x:X-type y:Y-Type z:Z-Type Attachments x.Out as z.Get y.In as z.Set End XYZ a component specification a component specification a connector specification The configuration between two components x and y via the connector z

8. Issues addressed • Specification of non-functional properties • Differentiate between the required properties from the ensured properties • Handling of multiple number of properties in one interface element.

9. Base construct • Base construct Non-functional Prop = (REQUIRES {provider.rrqmt}, ENSURES {port/role.erqmt}) • Is read as “The non-functional property Proprequires rrqmt from provider and ensures erqmt on port/role.” • Non-functional, REQUIRES, andENSURESare Wright reserved words • Propis a variable to be replaced with a non-functional property • REQUIRESindicates that the component or connector must receive from its environment • ENSURESindicates that component or connector must provide to its environment • a CSP notation for ‘contains’

10. Furthering the construct • Multiple Unrelated Requirements Non-functional Prop = (REQUIRES {providera.rrqmta}, REQUIRES {providerb.rrqmtb}, ENSURES {port/role.erqmt}) • Multiple Related Requirements Non-functional Prop = (REQUIRES {providera.rrqmta; providera.rrqmtb; providera.rrqmtc}, ENSURES {port/role.erqmt})

11. Furthering the construct – cont’d • Empty Set & Mathematical Notation Non-functional Prop = (REQUIRES {}, ENSURES {port/role.erqmt > x}) • “All” operator Non-functional Prop = (REQUIRES {all.rrqmt}; ENSURES {all.erqmt})

12. Example • Fictional e-healthcare system • 3 components, 3 connectors

13. Example – cont’d • Components - Existing Component GP Port authenticate = authenticate?x  authenticate Port write = start  accept!x  write Computation authenticate.authenticate?x  write.start  computation Component SP Port patient_test_data = data?x  patient_test_data Port compute_diagnosis = start  data!x  compute_diagnosis Computation=patient_test_data.data?xcompute_diagnosis.startcomputation Component PH Port diagnosis = diagnosis?x  diagnosis Port prescription=start  diagnosis!x  prescription Computation = diagnosis.diagnosis?x  prescription.start  computation

14. Example – cont’d • Components with Construct Component GP Port auth = authenticate?x  auth Port write = start  accept!x  write Computation auth.authenticate?x  write.start  computation Non-functional Security = (REQUIRES {Remote_Procedure_Call.encryption}, ENSURES {auth.authentication}) Component SP Port patient_test_data = data?x  patient_test_data Port compute_diagnosis = start  data!x  compute_diagnosis Computation = patient_test_data.data?x  compute_diagnosis.start  computation Non-functional Performance = (REQUIRES {Pipe.BufferSize ≥ 50KB; Pipe.ReadSpeed ≥ 1MB/sec}, ENSURES {}) Component PH Port diagnosis = diagnosis?x  diagnosis Port prescription = start  prescription!x  prescription Computation = diagnosis.diagnosis?x  prescription.start computation Non-functional Security = (REQUIRES {}, ENSURES {Prescription.encryption})

15. Exmaple – cont’d • Connectors - Existing Connector Shared_Variable Role GetTestData = accept?x  GetTestData Role GiveTestData = data!x  GiveTestData Glue = GetTestData.accept?x  GiveTestData.data!x  Glue Connector Pipe Role GetDiagnosis = data?x  GetDiagnosis Role GiveDiagnosis = diagnosis!x  GiveDiagnosis Glue = Getdiagnosis.data?x  GiveDiagnosis.diagnosis!x  Glue Connector Remote_Procedure_Call Role GetDiagnosis = diagnosis?x  GetDiagnosis Role GivePrescription = prescription!x  GivePrescription Glue = GetDiagnosis.diagnosis?x  GivePrescription.prescription!x  Glue

16. Example – cont’d • Connectors with Construct Connector Shared_Variable Role GetTestData = accept?x  GetTestData Role GiveTestData = data!x  GiveTestData Glue = GetTestData.accept?x  GiveTestData.data!x  Glue Non-functionalSecurity =(REQUIRES{GP.authentication}, ENSURES{}) Availability = (REQUIRES {}, ENSURES {GetTestData.WhenRead != GiveTestData.Write; GiveTestData.WhenWrite != GetTestData.Read}) Connector Pipe Role GetDiagnosis = data?x  GetDiagnosis Role GiveDiagnosis = diagnosis!x  GiveDiagnosis Glue = Getdiagnosis.data?x  GiveDiagnosis.diagnosis!x  Glue Non-functional Performance = (REQUIRES {}, ENSURES {GiveDiagnosis.BufferSize ≥ 50KB; GiveDiagnosis.ReadSpeed ≥ 1MB/sec}) Connector Remote_Procedure_Call Role GetDiagnosis = diagnosis?x  GetDiagnosis Role GivePrescription = prescription!x  GivePrescription Glue = GetDiagnosis.diagnosis?x  GivePrescription.prescription!?x  Glue Non-functional Security = (REQUIRES {}, ENSURES {.encryption })

17. Lacks formal rigidity String-like representation of non-functional properties Possibility for redundancy when one requirement pertains to more than one non-functional attribute Difficulty in defining and quantifying the non-functional properties in terms of a continuos scale. Limitations