Defining the measures

INRIA-Futurs, 05 Nov 2004

Defining the measures

From the begining, we have to make the distinction between two differents points of view on the measures: the user viewpoint and the system viewpoint. From the user's point of view, we are concerned of the characteristics and the metrics which can be observed and which have a direct influence on the user: the quality of services, the ease of use and the costs. From the system point of view, the measures concern the system's architecture, for example at the mirrors level. In the first step we shall focus on the user's viewpoint.

We have studied some ISO standards propossed for the measurement process (in general, such as: production process, distribution process, etc.) and we tried to aply the methodology on our particular case of software distribution. As a general rule, we have to define first the goal(s) of measurement. A quality model has to be chosen afterwards and we have to built up a tree of characteristics.

After a long discussion on the goals of EDOS project, we have accordingly defined the goals of measurement as follows: Two major goals are identified, namely to improve the quality of services (from the user viewpoint) and to lower the administration costs (from the system viewpoint).

I) Improve the QUALITY OF SERVICES

• for a new version we define:
• the FRESHNESS of the version - expressed as delay (time distance)

DEF: how fresh is the version that the user gets it (with notification) in respect to the reference version available at the moment when the user adressed his request.

• the CONSISTENCY of the version - expressed as distance (edit distance)

DEF: the edit distance between the user's version and the reference version completely consistent and coherent.

• for the ease of use we define:

a) the TIME needed to get a new version - influenced by the parameters as availability of the resource, speed of the transfer, size of the resource. This measure is highly dependent on the characteristics of the resource requested by the user. b) the EFFORT needed to get a new version - reflected in two actions find the source, the choice of the mirror. c) the user's COST - expressed in: space, runtime and bandwidth.

II) Lower the COSTS:

• space, runtime and bandwith (from the system viewpoint)

As a complementary comment, the customize and atomicity aspects can apply to all the parameters defined above.

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Another remark that came up was concerning the need of distinction that we have to make between the different categories of users that we address. Therefore, we distinguished three categories of users:

• Developers: the users that actively contribute to the developement of the new Mandrakelinux release. This ones are interested on the very last versions of software, even that the consistency is not fully guaranteed.
• Regular users: the users that need stable versions.
• Custom users: particular users that request customized versions of software.

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Topics Wp4 Wp5

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