Service identification and description. 2 Copyright e-Government Program (Yesser) Service...

Service identification and description

Copyright e-Government Program (Yesser) 2

Service identification - Summary Slide

Definition - Service Definition - Interface

Service interface – operation - parameters Example of a service What needs documenting?

From specification to design Service identification + description - the process

Identify Service operations Naming: Service operations Naming: Service operations

Add service operations to the use case steps Create descriptions

Audit Use cases and term model


Definition - Service

A service is executable software which offers a well-defined interface, accessible to other, independently developed and functioning, pieces of softwareA service displays functionality for others in form of operations

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A service has the following properties Use:

A (business) service only exists if the business understands it The service user does not need to know anything but the ”service

agreement” for using the service The service is autonomous – loosely coupled – without a state The service works independently, i.e. that one use of the service is

independent of other uses and of user context Services are a standardised way of modelling functionality across suppliers

and platforms

Technical: Services can be access from all platforms through a well-defined interface There are several ways of implementing a service – e.g. web service Service data can only be accessed through its operations

Thus it is not allowed to access service data by going around the operations (join across service tables is forbidden)


Definition - Interface The interface of the receiving system, to which the using systems must relate and refer

Used in several different places in IT architecture: Between human and computer (e.g. GUI) Between programs Between other elements in IT architecture

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Service interface – operation - parameters

The service interface has the following properties Service contact with the outside world Consists of operations and input / output parameters The interface must be well-documented The interface must be on display and easily accessible

Operations: Operations are the service functionality Without operations, no functionality

Input parameters: The data elements (attributes), which the operation needs to be able to perform

the specified functionality

Output parameters: The data elements (attributes), which the operation returns after performing the

specified functionality


Example of a service

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InterfaceCustomer

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What needs documenting?

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Service description

Service operation description

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From specification -> design

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Logical layer

<definitions xmlns="http://schemas.xmlsoap.org/wsdl/" ……<message name=“CreateRequest"> …… </message><message name=“CreateResponse"> …… </message><message name=“CreateFault"> …… </message>………..<operation name=”Create" parameterOrder="arg1"> <documentation>OpRegister customer in customer file index</documentation> <input name=" CreateRequest " message="tns: CreateRequest " /> <output name=" CreateResponse " message="tns: CreateResponse " /> <fault name="Fault" message="tns: CreateFault " /> </operation> ……….<service name=“Customer"> <documentation> Short service description </documentation> ……. </service>

</definitions>

Operational layer

WSDL = ”Service contract”

Send

List


Service identification + description - the processA

gen

cy

Completedescriptions

Initial state:- use cases identified and specified

Final state:- All services identified and documented

AllServices

Finished ?yesno

Audit Use casesand term model

IdentifyServiceoperations

Link to:-Use Case modeling-Term modeling


Identify Service operations

Identify Service operations For each use case, add service operations Generalise Services – think big picture, consider reuse Create services and operations in the service catalogue Categorise services


Naming: Service operations

Service operations are composed as follows: Term.Sub term_Operation

Term: The term describes an overall operational object, present in the term model. The term is

also the name of the service. The term is never in plural form.

Sub term: The sub terms belongs to the overall operations object; e.g. customer- optional, where

Optional is a sub term to Vehicle. The sub term is only used when it does not represent the overall term that relates to the operation – it is equipment that needs listing/getting/registering, not the vehicle itself.The sub terms is never in plural form, and is separated from the overall term by a ”.” (period).

Operation: The operation is the description fo the task the service performs, e.g. Get, Create, List,

Correct. The list of operations is not final, but will at first be kept at a minimum – though it is vital that the operation that the operation covers the actual task the service provides. If there is no operation to cover the task, one must ”invent” a new oneThe operation is referred to as an imperative verb, and separated from the sub term by a ”_” (underscore). If there is no sub term, use a ”.” to separate operation from overall term.


Naming: Service operations

Read: Read is used to acquire (read) data, an instance, from a data source List: Lists the instances in the database. Create: Creates a new instance, and saves it to a database. Only instances that have

been created can subsequently be retrieved (Get).Update: Update makes content changes to an already created instance.Send: Sends data to a given recipient, when it is necessary to push data.Delete: This operation deletes an instance.


Example of service description template


Example of template for service operation description


Add service operations to the use case steps


Create descriptions

Create descriptions Describe the service Describe the operations Add input and output parameters for each operation –

typically harvested from term model


Audit Use cases and term model

Revise Use cases If there is a need for use case changes, these are re-

vised on the go Make use of professional specialists

Revise the term model If there is a need for term model changes, these are re-

vised on the go Make use of professional specialists

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