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N Degrees of Separation:N Degrees of Separation:Multi-Dimensional Separation Multi-Dimensional Separation of Concern (MDSOC)of Concern (MDSOC)

HyperJ: language and HyperJ: language and concepts of general concern concepts of general concern combinationcombination

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Multi-dimensional Multi-dimensional separation of concerns separation of concerns (MDSOC)(MDSOC)

Multi dimensions separation of concerns refers to the ability to identify, encapsulate, and manipulate those parts of software that are relevant to a particular concern (concept, goal, purpose, etc.).

It helps supporting construction, evolution and integration of software.

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Types of concernsTypes of concerns::

The prevalent concern in object-oriented programming is the class, which encapsulates data concerns.

Feature concerns, like printing, persistence, and display capabilities, are also common.

Aspects, roles, variants, and configurations.

Concern means “a particular area of interestConcern means “a particular area of interest” ”

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Multi-dimensional Multi-dimensional separation of concerns separation of concerns (cont.)(cont.) Its goals are to enable:

Encapsulation of all types of concerns in a software system, simultaneously.

Overlapping and interacting concerns. On-demand remodularization.

It compliments existing formalisms, giving developers additional modularization flexibility while continuing to use the formalisms of their choice.

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Hyper/JHyper/J

Hyper/J supports multi-dimensional separation of concerns for JavaTM.

It provides: Ability to specify modules according to

concerns. Synthesize systems and components by

integrating those modules.

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Personnel Software - Personnel Software - RequirementsRequirements

Personnel feature: name Print

Business rules: 1-3 managers for each employee

The payroll feature: Salary information Tax regulations minimum and maximum wage.

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Personnel Software – Personnel Software – Class hierarchyClass hierarchy

name()print()check()position()pay()

EmployeeEmployee

name()print()check()position()pay()

SalesSalesname()print()check()position()pay()

ResearchResearchname()print()check()position()pay()

StaffStaff

name()print()check()position()pay()

ResearchMgrResearchMgrname()print()check()position()pay()

SecretarySecretaryname()print()check()position()pay()

MaintenanceMaintenancename()print()check()position()pay()

SalesMgrSalesMgr

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The tyranny of the The tyranny of the dominant decompositiondominant decomposition

Existing formalisms provide only restricted sets decomposing and composing mechanisms, and these typically support only a single, “dominant” dimension of separation at a time.

We would like the system to encapsulate all relevant kinds (dimensions) of concerns simultaneously. MDSOC.

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Features are Scattered and Features are Scattered and TangledTangled Scattering – a single requirement affects multiple design and

code modules. Tangling – material pertaining to multiple requirements is

interleaved within a single module. In general:

Features are coherent entities from a conceptual and requirement point of view, BUT

Features are not modules in design or code So, I is difficult to:

Find and work with the code for a feature Add a new feature Remove a feature Mix-and-match features

In a Non-InvasiveNon-Invasive way!

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Hyper/J conceptsHyper/J concepts

HyperslicesHyperslices

HypermodulesHypermodules

HyperspacesHyperspaces

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SSetting the context and introducing etting the context and introducing terminology for Separation of Concernsterminology for Separation of Concerns

It is convenient to think of the descriptive material in each artifact as being made up of unitsunits. PrimitivePrimitive unitsunits – e.g. methods of a class, declarations.

A unit might also be a state chart or requirement specification– depending upon the artifact.

CompoundCompound unitsunits or modulesmodules – e.g. classes, interfaces. A single concept is typically modeled by a

collection of many units (primitive or compound).

A single unit often participates in modeling more than one concept.

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Multi-Dimensional Multi-Dimensional Decomposition: Decomposition: HyperslicesHyperslices

A hyperslicehyperslice is a set of units. Hyperslices are intended to encapsulate

concerns in dimensions other than the dominant one.

The modules within it contain all, and only, those units that pertain to a given concern.

Hyperslices can overlap – a given unit may occur in multiple hyperslices.

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Hyperslices in the Hyperslices in the personnel softwarepersonnel software::

position()pay()

EmployeeEmployee

position()pay()

SalesSalesposition()pay()

ResearchResearchposition()pay()

StuffStuff

position()pay()

ResearchMgrResearchMgrosition()pay()

SecretarySecretaryposition()pay()

MaintenanceMaintenanceposition()pay()

SalesMgrSalesMgr

PayrollPayrollhyperslicehyperslice

name()check()print()

EmployeeEmployee

name()check()print()

SalesSalesname()check()print()

ResearchResearchname()check()print()

StuffStuff

name()check()print()

ResearchMgrResearchMgrname()check()print()

SecretarySecretaryname()check()print()

MaintenanceMaintenancename()check()print()

SalesMgrSalesMgr

PersonnelPersonnel hyperslicehyperslice

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Multi-Dimensional Multi-Dimensional Decomposition: Decomposition: HypermodulesHypermodules

Each hypermodulehypermodule is composed of: A set of hyperslices hyperslices A composition rulecomposition rule that specifies how

the hyperslices are to be integrated.

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Multi-Dimensional Multi-Dimensional Decomposition: Decomposition: HyperspacesHyperspaces A hyperspacehyperspace is a concerns space whose

structure supports our approach to multi-dimensional separation of concerns.

Concerns are grouped into dimensions, giving hyperspaces an explicitly multi-dimensional structure.

A dimension of concern is a set of concerns that are disjoint (i.e., they have no units in common).

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Personnel Software - Personnel Software - HyperspacesHyperspaces

CodeCode

Class

Feature

Employee Research Sales SecretaryEmployee Research Sales Secretary

Artifact

PayrollPayroll

PersonnelPersonnel

RequirementsRequirements

DesignDesign

The Hyperspace is a multi dimensional The Hyperspace is a multi dimensional space.space.

Axes are dimensions of concernAxes are dimensions of concern Points on axes are concernsPoints on axes are concerns Software units fall at points in the spaceSoftware units fall at points in the space

Encapsulation and composition via Encapsulation and composition via HyperslicesHyperslices and and HypermodulesHypermodules

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Hyperspaces (cont.)Hyperspaces (cont.) A hyperspace can contain many

hypermodules realizing different modularizations of the same units.

Systems can be composed in many

ways from hypermodules.

Hypermodules are not, in general, complete, executable programs.

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Hyperspaces - AdvantagesHyperspaces - Advantages The explicit identification of concerns and

dimensions, and the alignment of units according to concerns, are significant aids to comprehensibilitycomprehensibility.

Hyperspaces are intended to include artifacts from all phases of the software lifecycle (e.g., requirements, design, code), and the alignment of units promotes traceabilitytraceability.

Changes that add functionalityChanges that add functionality can always be accomplished by adding new units, and either including them within existing hypermodules or adding new hypermodules.

The structure of hypermodules and their composition rules significantly limits the impact of limits the impact of all changesall changes.

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Using Hyper/JUsing Hyper/J – – for personnel softwarefor personnel software

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Class

Feature

Employee Research Sales SecretaryEmployee Research Sales Secretary

PersonnelPersonnel

name()

check()

print()

position()

pay()

Employee

Research

Sales Secretary

Basic Personnel hyperspaceBasic Personnel hyperspace

name()

check()

print()

position()

pay()

name()

check()

print()

position()

pay()

name()

check()

print()

position()

pay()

hyperspace payrollPlusPersonnel composable class Personnel;*.

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Different organization – Different organization – Different requirementsDifferent requirements

No need for payroll information

Different business rules Each employee

must have exactly one manager.

Mix-and-match the payroll feature.

Modify an existing well-formed constraint

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On-demand On-demand remodularizationremodularization

Hyper/J permits developers to identify and noninvasively encapsulate new concerns at any time Including concerns that are scatterd

across, and tangled within existing software.

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On-demand On-demand remodularizationremodularization The developer needs to identify those pieces of the

existing software that are part of the new concern(s)

And express this information in Hyper/J using a concern mappingconcern mapping:

packagepackage Personnel: Feature.Personnel Personnel: Feature.Personneloperationoperation position: Feature.Payroll position: Feature.Payroll operationoperation pay: Feature.Payroll pay: Feature.Payroll

By default, all members of the classes and interfaces in the Java package Personnel belong to the personnel concern in the feature

dimensionThe subsequent statements

override this to say:Any method named position position or

paypay belongs to the payroll concern in the feature

dimension )irrespective of its class(

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Hyper/J creates a hyperslice for each featureHyper/J creates a hyperslice for each feature ))each roweach row((

name()

check()

print()

name()

Position()

pay()

Identification of ConcernsIdentification of Concerns

name()

Position()

pay()

name()

Position()

pay()

name()

Position()

pay()

Class

Feature

Employee Research Sales SecretaryEmployee Research Sales Secretary

PayrollPayroll

PersonnelPersonnelname()

check()

print()

name()

check()

print()

name()

check()

print()

Employee

Research

Sales Secretary

Employee

Research

Sales Secretary

public float pay() {System.out.println ( “Paying” + name() );return _salary; }

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Declarative CompletenessDeclarative Completeness

name()

Position()

pay()

name()

Position()

pay()

name()

Position()

pay()

Class

Feature

Employee Research Sales SecretaryEmployee Research Sales Secretary

PayrollPayroll

PersonnelPersonnelname()

check()

print()

name()

check()

print()

name()

check()

print()

name()

check()

print()

Employee

Research

Sales Secretary

name()

Position()

pay()

Employee

Research

Sales Secretary

Hyper/J inserts abstract declarations for any membersHyper/J inserts abstract declarations for any members referred to, but not implemented within the hyperslicereferred to, but not implemented within the hyperslice

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Composing hyperslicesComposing hyperslices

The developer needs to write a hypermodule declaration:

hypermodule PayrollPlusPersonnelhypermodule PayrollPlusPersonnel hyperslicehyperslice: : Payroll, Personnel;

relationshiprelationship: mergeByName;end hypermoduleend hypermodule

Name the hypermodule

List of hyperslices to be composed

The relationship section lists all the ways in which the

hyperslices are related

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Class

Feature

Employee Research Sales SecretaryEmployee Research Sales Secretary

PayrollPayroll

PlusPlus

PersonnelPersonnel

name()

check()

print()

position()

pay()

Employee

Research

Sales Secretaryname()

check()

print()

position()

pay()

name()

check()

print()

position()

pay()

name()

check()

print()

position()

pay()

Composing hyperslices Composing hyperslices (cont.)(cont.)

What happened with the method name()?PayrollPlusPersonnel.Emplo

yee

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Composing – general Composing – general strategiesstrategies mergeByName

Units in different hyperslices, that have the same name correspond and should be merged.

nonCorrespondingMerge Units in different hyperslices accidently

have the same name, but are not actually related to one another.

This strategy does not work correctly and is disabled! overrideByName

The last unit (according to the specification order) should override the others.

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What about the changes What about the changes to the business rulesto the business rules??

method Personnel.Employee.check : BusinessRule.ThreeManagers

Creates a new dimensiondimension: BusinessRule And creates the ThreeManagersThreeManagers concernconcern

on that dimension.

method SingleManagerPkg.Employee.check: BusinessRule.OneManager

Creates the OneManagers concernOneManagers concern on that dimension.

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Changes for Business Changes for Business RulesRules

Feature

NoneNone

Class

PayrollPayroll

PersonnelPersonnel

Business Rule

ThreeThreeManagersManagers

OneOneManagerManager

Position()

pay()

Employee

name()

check()

print()

Employee

check()

Employee

check()

Employee

Compose for new one-manager check

Compose for original3 managers check

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HyperJ - summaryHyperJ - summary With HyperJ, a program can be decomposed according to

different concerns. New separate modules can be created, in standard Java,

that encapsulate concerns from scratch, without modifying the rest of the program or interfering with the work of other developers.

Modules can also be extracted from existing Java programs.

Selections of these modules can then be integrated to yield programs that are executable on standard JVMs.

Multiple system decompositions can be created simultaneously and new decompositions added at any stage of the software development lifecycle.

HyperJ helps in managing the interactions across different decompositions. HyperJ also provides a powerful composition capability, which can be used to combine separated concerns selectively into an integrated program or component.

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Hyper/J vs. Aspect/JHyper/J vs. Aspect/J Hyper/J is a tooltool Aspect/J is a languagelanguage

Hyper/J supports integration of multiple models Aspect/J supports augmentation of single model

Hyper/J – composing and decomposing can be done at any time.

Aspect/J – incremental changes only