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32 1 Hierarchies and Relationships

Summary

• Namespaces organize multiple vocabularies so that they may be used at
  the same time.


• Namespaces are URIs that are declared in an XML document.


• Each namespace is either the default namespace or it has an abbreviation
  called a prefix.


• Element names and attributes may be qualified by using the namespace
  prefix.


• The default namespace applies to all unqualified elements. It does not
  apply to unqualified attributes.

1.8 Exercises

1. A spreadsheet was exported in comma-delimited format. The first few
   lines look like this:

element_id,sequence_id,organism_name,seq_length,type

U83302,MICR83302,Colaptes rupicola,1047,DNA

U83303,HSU83303,Homo sapiens,3460,DNA

U83304,MMU83304,Mus musculus,51,RNA

U83305,MIASSU833,Accipiter striatus,1143,DNA

Show how these records would be written as XML elements using the

bio_sequencetag.

2. For the spreadsheet in exercise 1.1 above, show the corresponding XML
   DTD. Theelement_idattribute is a unique key for the element. As-
   sume that all attributes are optional. The molecule type is restricted to the
   biologically significant types of biopolymer.


3. Here is a relational database table that defines some physical units: