Similarity: a point, feature, or detail in which two items are alike
Self-similarity: the property of having a substructure analagous or identical to an overall structure [WHOLE: windowframes neighbouring skyscrapers are viewed diamondlike in perspective /IN BETWEEN: diamond curtain wall of library / PART: diamond grid]
[definition of similarity and self-similarity by thefreedictionary.com]
[Interpretation of photos of Seattle library by architect OMA, 2004]