Each HOMS component is given a unique component number by which it may be referenced. So that these numbers may be of help to users in locating the components they require, part of the component number is a subject classification code for the components. For the purpose of this classification the subject matter of HOMS is divided into 14 sections each designated by a letter. These sections largely follow the major sequence of activities of an operational hydrological service. Sections are subdivided into subsections each of which is given a two digit numeric code. For example H09 denotes a subsection of section H Primary Data Processing, and happens to contain components dealing with the primary processing of sediment transport data.
HOMS aims to provide components for users at all levels of development, therefore the components available must range from the simplest to the most complex. This range is reflected in the component number. Each component is assigned a level of complexity denoted by a single digit in the range 1 to 3. Level 1 is the lowest level of complexity and contains the simplest components. Level 3 denotes the most complex components while components with level of complexity 2 are of intermediate complexity. In certain sections this concept of level of complexity was not judged appropriate and no levels of complexity have been assigned to the components in these sections. In these cases the level of complexity is shown as zero in the component number.
The component number is completed by a two-digit serial number, used only to distinguish components in the same subsection and level of complexity from each other. The complete component number is written in a form similar to the following coding:
S represents a letter (A to L, X or Y) denoting a section, nn is a two-digit subsection number, c is a one-digit level of complexity (1, 2 or 3), xx is a two-digit serial number.
As an example note that component H76.2.05 is in section H, subsection H76, is of medium complexity (level 2) and has serial number 05 .
Each HOMS component description contains three dates, one under the component's number at the top right, and two at the bottom of the description. Their respective meaning is the following:
Bottom left: Date first entered, date in which the component was first entered in the HRM, possibly in a different version that the current one;
Bottom right: Date last updated, date on which the component's description last underwent changes.
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