# Metadata Management Accessing and modifying metadata of text documents and corpora. ```r ## 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 [https://dublincore.org/documents/dces/](https://dublincore.org/documents/dces/)). ## See Also `meta` for metadata in package `NLP`. ## References Dublin Core Metadata Initiative. [https://dublincore.org/](https://dublincore.org/) ## Examples ```r 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) ```

meta function