We consider here the class of compact , isolated , high–velocity H i clouds , CHVCs , which are sharply bounded in angular extent with no kinematic or spatial connection to other H i features down to a limiting column density of 1.5 \times 10 ^ { 18 } cm ^ { -2 } .
We describe the automated search algorithm developed by de Heij et al .
( 2002a ) and applied by them to the Leiden/Dwingeloo Survey north of \delta = -28 ^ { \circ } and by Putman et al .
( 2002 ) to the Parkes HIPASS data south of \delta = 0 \hbox { $ { } ^ { \circ } $ } , resulting in an all–sky catalog numbering 246 CHVCs .
We argue that these objects are more likely to represent a single phenomenon in a similar evolutionary state than would a sample which included any of the major HVC complexes .
Five principal observables are defined for the CHVC population : ( 1 ) the spatial deployment of the objects on the sky , ( 2 ) the kinematic distribution , ( 3 ) the number distribution of observed H i column densities , ( 4 ) the number distribution of angular sizes , and ( 5 ) the number distribution of line widths .
We show that the spatial and kinematic deployments of the ensemble of CHVCs contain various clues regarding their characteristic distance .
These clues are not compatible with a location of the ensemble within the Galaxy proper .
The deployments resemble in several regards those of the Local Group galaxies .

We describe a model testing the hypothesis that the CHVCs are a Local Group population .
The agreement of the model with the data is judged by extracting the observables from simulations , in a manner consistent with the sensitivities of the observations and explicitly taking account of Galactic obscuration .
We show that models in which the CHVCs are the H i counterparts of dark–matter halos evolving in the Local Group potential provide a good match to the observables , if account is taken of tidal and ram–pressure disruption , the consequences of obscuration due to Galactic H i and of differing sensitivities and selection effects pertaining to the surveys .

A representative sample of CHVCs has been studied with high angular resolution ( sub-arcminute ) using the WSRT and with high N _ { HI } sensitivity ( < 10 ^ { 17 } cm ^ { -2 } ) using the Arecibo telescope .
The picture that emerges is a nested morphology of CNM cores shielded by WNM cocoons , and plausibly surrounded by a Warm Ionized Medium halo .
These observations lead to indirect contraints on the distances , ranging from 150 to 850 kpc .