R: Metadata Management

meta {tm} | R Documentation

## Metadata Management

### Description

Accessing and modifying metadata of text documents and corpora.

### Usage

    ## S3 method for class 'PCorpus'
    meta(x, tag = NULL, type = c("indexed", "corpus", "local"), ...)
    ## S3 replacement method for class 'PCorpus'
    meta(x, tag, type = c("indexed", "corpus", "local"), ...) <- value
    ## S3 method for class 'SimpleCorpus'
    meta(x, tag = NULL, type = c("indexed", "corpus"), ...)
    ## S3 replacement method for class 'SimpleCorpus'
    meta(x, tag, type = c("indexed", "corpus"), ...) <- value
    ## S3 method for class 'VCorpus'
    meta(x, tag = NULL, type = c("indexed", "corpus", "local"), ...)
    ## S3 replacement method for class 'VCorpus'
    meta(x, tag, type = c("indexed", "corpus", "local"), ...) <- value
    ## S3 method for class 'PlainTextDocument'
    meta(x, tag = NULL, ...)
    ## S3 replacement method for class 'PlainTextDocument'
    meta(x, tag = NULL, ...) <- value
    ## S3 method for class 'XMLTextDocument'
    meta(x, tag = NULL, ...)
    ## S3 replacement method for class 'XMLTextDocument'
    meta(x, tag = NULL, ...) <- value
    DublinCore(x, tag = NULL)
    DublinCore(x, tag) <- value

### Arguments

`x` | For `DublinCore` a `TextDocument`, and for `meta` a `TextDocument` or a `Corpus`.
`tag` | a character giving the name of a metadatum. No tag corresponds to all available metadata.
`type` | a character specifying the kind of corpus metadata (see Details).
`...` | Not used.
`value` | replacement value.

### Details

A corpus has two types of metadata. Corpus metadata (`"corpus"`) contains corpus specific metadata in form of tag-value pairs. Document level metadata (`"indexed"`) contains document specific metadata but is stored in the corpus as a data frame. Document level metadata is typically used for semantic reasons (e.g., classifications of documents form an own entity due to some high-level information like the range of possible values) or for performance reasons (single access instead of extracting metadata of each document). The latter can be seen as a from of indexing, hence the name `"indexed"`. Document metadata (`"local"`) are tag-value pairs directly stored locally at the individual documents.

`DublinCore` is a convenience wrapper to access and modify the metadata of a text document using the Simple Dublin Core schema (supporting the 15 metadata elements from the Dublin Core Metadata Element Set http://dublincore.org/documents/dces/).

### References

Dublin Core Metadata Initiative. http://dublincore.org/

### See Also

`meta` for metadata in package NLP.

### Examples

    data("crude")
    meta(crude[[1]])
    DublinCore(crude[[1]])
    meta(crude[[1]], tag = "topics")
    meta(crude[[1]], tag = "comment") <- "A short comment."
    meta(crude[[1]], tag = "topics") <- NULL
    DublinCore(crude[[1]], tag = "creator") <- "Ano Nymous"
    DublinCore(crude[[1]], tag = "format") <- "XML"
    DublinCore(crude[[1]])
    meta(crude[[1]])
    meta(crude)
    meta(crude, type = "corpus")
    meta(crude, "labels") <- 21:40
    meta(crude)

[Package tm version 0.7-5 Index]