#+TITLE: PicaRecord -- Object oriented interface to Pica+ records #+AUTHOR: David Maus #+EMAIL: maus@hab.de * About PicaRecord provides an object oriented interface to Pica+ records, fields, and subfields. It does not provide the means to read or write Pica+ records. In order to do so you need to install the packages PicaReader and PicaWriter that are available via the same PEAR channel. PicaRecord is copyright (c) 2012 by Herzog August Bibliothek Wolfenbüttel and released under the terms of the GNU General Public License v3. * Installation PicaRecord should be installed using the [[http://pear.php.net][PEAR Installer]]. This installer is the PHP community's de-facto standard for installing PHP packages. #+BEGIN_EXAMPLE pear channel-discover hab20.hab.de/service/pear pear install --alldeps hab20.hab.de/service/pear/PicaRecord #+END_EXAMPLE PicaRecord depends on the [[http://phix-project.org/][Phix project's]] PSR0 compliant autolader, =Autoloader=. * Usage ** Records, Fields, and Subfields *** Subfields Subfields are represented by the =Subfield= class. A Pica+ subfield is a cons (pair) of an alphanumeric case-sensitive ASCII character and a non-empty string value. The code of a subfield is considered to be immutable and the value must not be the empty string. *** Fields Field are represented by the =Field= class. A Pica+ field is an ordered list of subfields and partially identified[1] by two properties, the field tag and the field occurrence. Both properties are set on instantiation and considered to be immutable. In the following text the /field shorthand/ refers to a string consisting of the field tag, followed by a forward slash (ASCII 47) followed by two digits denoting the field occurrence. For example the field shorthand of the field 021A with an occurrence of 0 is =021A/00=. **** Retrieving subfields =Field::getSubfields()= returns all subfields of a field when called with no arguments. To retrieve specific subfields you can pass an arbitrary number of arguments each representing a subfield code. If you do so the returned array will be constructed as follows: Each element of the returned array corresponds to a subfield code in the argument list. If the field has a subfield with the specified code the element of the returned array contains the subfield. If the field does not have a subfield with the specified code the element of the returned array contains =NULL=. In order to retrieve multiple subfields with the same subfield code you need to repeat the subfield code in the argument list. The first occurrence of the code in the argument list refers to the first subfield with the specified code, the second occurrence to the second subfield and so on. Because =Field::getSubfields()= when called with subfield codes as arguments returns an array with a known size (as much elements as arguments were passed to the function) you can conveniently use PHP's =list()= operation. Example: To retrieve the first and last name of the author encoded in the Pica+ field =028A/00= you can call =Field::getSubfields()= as follows: #+BEGIN_EXAMPLE list($firstName, $lastName, $personalName) = $field->getSubfields('d', 'a', '5'); #+END_EXAMPLE **** Manipulating the subfield list You can use =Field::addSubfield()= to add a field to the end of the subfield list. If the subfield is already part of the subfield list an =InvalidArgumentException= is thrown. For more sophisticated manipulations of a field's subfield list you can use =Field::setSubfields()= to replace the subfield list of a field. A subfield can be deleted using =Field::removeSubfield()= which takes the subfield to delete as sole argument and throws an =InvalidArgumentException= if the field does not contain the subfield. *** Records **** Record classes PicaRecord provides classes for the four record types of /title records/, /authority records/, /local records/, and /copy records/. The relationship of title, local, and copy records is as follows: A title record may contain zero or more local records. Each local record may contain up to 99 copy records. Local records can be identified by the internal library number (ILN) of the library they belong to and retrieved either by =TitleRecord::getLocalRecord()=, which returns an array of all local records, or =TitleRecord::getLocalRecordByILN()= which retrieves a single local record identifed by its first argument. Copy records hold information about particular items (exemplars) and are identified by the number of the item in the local record. You can use =LocalRecord::getCopyRecords()= or =LocalRecord::getLocalRecordByItemNumber()= to retrieve an array with all copy records or a single copy record with a specified item number respectively. All record classes implement the two methods =Record::isEmpty()= which returns =TRUE= if a record is empty (does not contain any fields) and =Record::isValid()= which performs a preliminary validation of the record. **** Selecting and deleting fields =Record::getFields()= returns all fields of the record when called without arguments. If you call it with the body of a regular expression as argument it will only return the fields whose shorthand is matched by the regular expression. =Record::select()= provides a more generic access to a record's fields. It takes a predicate function as argument and returns all fields that fullfill the predicate. A predicate function can be any valid PHP callback that takes a Field as argument and return TRUE if the field fullfills the predicate or otherwise FALSE. =Record::delete()= deletes all fields that match a predicate function (see above). If a record contains other records, i.e. if a record is a title or local record, =Record::delete()=, =Record::select()=, and =Record::getFields()= operate on all fields of the record, including the fields of the contained records. **** Appending fields to a record Append fields to an existing record is not as straightforward as selecting or deleting fields. Each record class has its own restrictions when it comes to appending a field to it via the =Record::append()= function: - you can only append fields with a level of 0 to title and authority records - you can append fields with a level of 1 to local records - you can only append fields with a level of 2 to copy records; as an additional restriction the occurrence value of the field must be equal to the item number of the copy record #+CAPTION: Allowed field levels per record class | Record class | Allowed field level in append() | |-----------------+---------------------------------| | TitleRecord | Level 0 | | AuthorityRecord | Level 0 | | LocalRecord | Level 1 | | CopyRecord | Level 2 | The attempt to add a field with a different level then the allowed level results in an =InvalidArgumentException= to be thrown. * Development If you want to patch or enhance this component, you will need to create a suitable development environment. The easiest way to do that is to install phix4componentdev: #+BEGIN_EXAMPLE apt-get install php5-xdebug apt-get install php5-imagick pear channel-discover pear.phix-project.org pear -D auto_discover=1 install -Ba phix/phix4componentdev #+END_EXAMPLE You can then clone the Git repository: #+BEGIN_EXAMPLE git clone git://gitorious.org/php-pica/picarecord.git #+END_EXAMPLE Then, install a local copy of the package's dependencies to complete the development environment: #+BEGIN_EXAMPLE phing build-vender #+END_EXAMPLE To make life easier for you, common tasks (such as running unit tests, generating code review analytics, and creating the PEAR package) have been automated using [[http://phing.info][Phing]]. You'll find the automated steps inside the build.xml file that ships with the component. Run the command 'phing' in the component's top-level folder to see the full list of available automated tasks. * Acknowledgments The [[http://phix-project.org][Phix project]] makes it easy to setup and maintain a package repository for a PEAR-installable package and integrates important tools such as [[http://phpunit.de][PHPUnit]], [[http://phing.info][Phing]], [[http://pear.php.net][PEAR]], and [[http://pirum.sensiolabs.org/][Pirum]]. Large parts of this package would not have been possible without studying the source of [[http://search.cpan.org/dist/PICA-Record/][Pica::Record]], an open source Perl library for handling Pica+ records by Jakob Voß, and the practical knowledge of our library's catalogers. * Footnotes [1] E.g. a title record may contain zero or more fields with tag =101@= and occurrence =00=; fields with this shorthand indicate the start of a local record.